Natural and Man-Made Fibres

Transcription

1 Natural and Man-Made Fibres Sangita Srivastava, M.Sc., D.Phil. Associate Professor and Head Department of Home Science University of Allahabad Allahabad, India Pushpa Publishing House Vijaya Niwas, 198, Mumfordganj, Allahabad , India

2 Natural and Man-Made Fibres First Edition 2012 Pushpa Publishing House All rights reserved. No part of this book may be reproduced in any way or by any means without prior permission of the Publisher. ISBN-13: Price: INR Published and printed by Pushpa Publishing House, Vijaya Niwas, 198, Mumfordganj, Allahabad , India.

3 Dedicated to My Parents Professor R. N. Srivastava and Dr. Pratibha Srivastava

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5 Preface This book is being brought out for students who are pursuing courses in apparel and textile designing. Before taking a step towards apparel designing, it is of great importance to know about different textile fibres. The book covers in its varied chapters all details about fibres - natural and man-made. This book covers the story of all natural fibres beginning from where they are obtained, and how many processes the fibres undergo before the yarn making and fabric making process. It is interesting to study how each fibre has properties different from the other. A lot of fibre properties make an appearance in the fabric due to the environment in which the fibre was grown and also because of its molecular structure. Some changes on the surface of the fibre can be brought about by the use of finishes which enhance their appearance and make the fabrics perform better. I have tried my best to cover almost all man-made fibres and natural fibres to give a comprehensive detail about the properties each one of them possess, and how and where they are used. The author owes immense gratitude to Pushpa Publishing House, for publishing this book, and all those who have been involved in the shaping-up of this book. I am thankful to my research scholar Ms. A. Fatima for her constant help from time to time.

6 Preface I am greatly indebted to my husband Justice Vikram Nath for his constant encouragement and valuable advice. I should say he has been the wind beneath my wings. I am also thankful to my office staff Ms. Neeta for her understanding approach in the Department of Home Science, University of Allahabad at various testing times. I am sure that the students will find it as a useful and valuable book in the field of clothing and textile. Sangita Srivastava

7 Contents Chapter 1: Textile Fibres 1 Chapter 2: Cellulosic Fibre - Cotton 21 Chapter 3: Linen (Flax) - Cellulosic Fibre 31 Chapter 4: Minor Cellulosic Fibres 39 Chapter 5: Wool - The Protein Fibre 51 Chapter 6: Silk - The Queen of Textile Fibres 63 Chapter 7: The Non-Thermoplastic Man-Made Fibres - Rayon 79 Chapter 8: Man-Made Fibres 89 Chapter 9: Polyesters 105 Chapter 10: Yarn 119 Chapter 11: Finishing 131 Chapter 12: Laundry 143

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9 Chapter 1: Textile Fibres F ibres are the basic fundamental units which are the components of yarn. The yarn is then woven, knitted or bonded to make a fabric. All fibres have merits and demerits or we may say they are a mixture of good and bad qualities. There is no perfect fibre. One type of fibre cannot posses all good qualities. For example, if it is absorbent it will have no crease retention. Nylon is a strong fabric but it does not absorb moisture, hence it cannot be used in the summer months. Until the turn of twentieth century, all fibres were obtained from natural resources. The most common fibres into usage were cotton, silk, linen and wool. However, wool and linen were more in use because of easier manufacturing. Cotton was difficult to spin by hand because of its short length. Silk was always expensive. When spinning and weaving became power operations, cotton became the most widely used fabric. A position it holds even today. In the last hundred years, as new textile fibres are hitting the market every other day, the consumer is the king having umpteen choices to choose from. What should be the qualities of a good fibre? A fibre to be spinnable must have sufficient length, pliability, strength, and cohesiveness to form a yarn. Milkweed and kapok are examples of fibres that are too brittle to spin into yarns. Extremely long fibre or filaments need not be cohesive since the fibres are not spun into yarns in the conventional way. Fibres must also be abundantly available and constant in supply for use. All fibres are long and have diameter in microns. Natural fibres

10 Natural and Man-Made Fibres lack uniformity because of weather conditions, nutrition and soil fertility. That is why they vary in quality also. In today s world, researches are being done to produce textiles which can perform more technical functions. Nanotechnology has made headway in preparing a special jacket for soldiers. The textile will immediately sense blood on itself and convey message to the mobile phone which starts making emergency calls. Also, cotton fibres with stain resistance, which may require no laundry, have been prepared using nanotechnology. Man-made fibres are more uniform in size and quality because it is possible to control the entire production process. The production process can be varied or improvised as per requirement. Fibre weaknesses can be minimized during yarn production. Finishes are used to enhance texture, appearance and feel of the fabric. Nanotechnology has created a range of new textiles for medical and surgical purposes. Cotton is being made such that it catches no dirt and stain and also the softness and pliability of cotton is not altered because of this surface finish. Fibre structure Fibres differ from one another In physical structure includes length, diameter, surface contour, crimp, cross-section shape and molecular arrangement. Fibre length Fibres are obtained from the manufacturers in the following form. Filament Monofilament and multifilament Staple Natural 2

11 Textile Fibres Man-made staple Filament tow Filament Silk is the only natural filament fibre. All man-made fibres are extruded from the spinneret as filament, but some are reduced to staple and used in the form only. While others are used as both filament and staple. Yarns made from filament are of two types. Multifilament and monofilament. Multifilament yarns are made up of a number of tiny filaments twisted together. The size and number of the filament may vary. Yarns of this type are smooth and give a smooth surface texture, softness, lustre, luxurious drape. They are used in lingerie, blouses, and other dresses. Monofilaments yarns are composed of a single solid strand of great strength and smoothness. Very sheer hosiery is made from these monofilament yarns. Large monofilaments are used for car seat covers and screenings, also other such things. Staple fibre All staple fibres either natural or man-made are short in length, and are measured in inches. They range from three quarter of an inch to fifteen inches. The word staple derives meaning from the fourteenth century as a descriptive term for merchandize. Later it came to mean basic commodities in a particular business. Still later it was used to express the length of wool and cotton fibres. During World War I Germany began the practice of cutting artificial silk into short lengths for use in cotton and wool type fabrics as there was shortage of these fibres. The word staple as applied to these cut fibres and is now the standard name for any fibre of a length 3

12 Natural and Man-Made Fibres expressed in inches. All natural fibres with an exception of silk are staple. Filament tow Filament tow is a collection of many parallel filaments without twist which are grouped together in rope form. Light tow of 500 to 500,000 denier is made into staple fibre by the tow-to-top direct spinning system. The tow is fed into a machine through leveling rolls, passes between two rolls which travel at a faster rate of speed and create tension that causes the fibres to break at their weakest point. The strand is then drawn out to yarn size, twisted and wound on bobbin. Direct spun yarns have high degree of strength and uniformity than conventionally spun yarns. Dense compact rainwear fabrics can be made by using the direct spun yarns in the filling direction. When these shrink they bring the warp yarn closer. Man-made filament and staple are spun by different equipment, often in different factories, because of the different number of holes needed in the spinnerets. Fibre diameter The finer the diameter of a fibre the finer the fibre. The thicker the fibre the more body it has the stiffer it is. Fineness is a major factor in determining the quality. It is measured in microns. Diameter Range for Natural Fibres Cotton Flax Wool Silk 16 to 20 microns 12 to 16 microns 10 to 70 microns 11 to 12 microns 4

13 Textile Fibres The diameter of man-made fibres is determined according to end use. It is controlled by the size of the spinneret and by stretching during or after spinning. The fineness of the man-made fibre is measured in denier. For any fibre the higher the denier the more coarse the fibre. Surface contour refers to the surface of the fibre along its shaft. Natural fibres grow in certain shapes and are not uniform throughout their length. Man-made fibres within certain limitations can be made in any desired shape. They are exactly the same diameter throughout, they can be altered into thick or thin as per the requirement. Fibre shape is determined by end use. For blending natural fibre with, man-made the man-made fibre is prepared to be of the same thickness as that with which it has to blend. Wool is the only fibre which has a broken surface caused by overlapping sections like fish scales or shingles, no man-made fibre has so far been produced with the effect of broken surface. Cross-sectional shape The cross-sectional shape is important because it contributes to the surface appearance of the fibre. It contributes towards imparting properties like lustre, bulk, and body to the fibre. It also affects the hand or the feel of the fabric. Circular shape is achieved by extruding the spinning solution through circular holes, by melt spinning process. Or by stretching when it is wet. These fibres make compact rather than spongy yarns. Circular cross-sections with serrated edges result from shrinking of the fibre in a coagulating bath during wet spinning. Many serrations give high lustre. 5

14 Natural and Man-Made Fibres Figure 1.1. Cross-section of fibres. Polygonal shape is found only in flax. It gives lustre to the fibre. Oval Shape also gives good cover and a pleasing hand that is neither silky nor harsh. Triangular shape occurs in silk and has been achieved in some of the new man-made fibres by using a highly viscous solution, melt spinning through triangular holes, but it cannot be stretched after spinning. Lobular or multiform shape probably results from evaporation of the solvent during dry spinning. It gives a good hand. Dog bone or dumbbell makes wool like yarns and fabric. Flat ribbon like shape is used for crisp lustrous fabric and imitation straw. Wild silk is somewhat of this shape. Y shaped cross-section give excellent cover and bulk. It is used for stuffing where warmth is required. 6

15 Textile Fibres Hollow centre fibres give buoyancy. They are seldom used on clothing but are excellent for life jackets. Other fibre shapes are possible and if a new shape adds a new property to a fibre, it may well be prepared. The scope for further shapes is ever there. Crimp Crimp is that property of fibre which imparts waviness along the length of the fibre. Fibre crimp increases cohesiveness, resiliency, and resistance to abrasion and gives increased bulk to the fibre. A fibre may have mechanical crimp, natural or inherent crimp and latent or chemical crimp. Mechanical crimp Mechanical crimp is imparted by passing the fibres through fluted rollers to produce a two-dimensional wave. The bends in this crimp are angular as compared to rounded in the natural crimp fibres. To make the crimp permanent heated rollers are used. Natural crimp occurs in wool and cotton. Cotton has twodimensional twist called convolutions. Latent or chemical crimp Latent or chemical crimp exists in the fibre in an under developed state. Until the garment is immersed in water and it coils and curls. Some of the man-made fibres like rayon, acetates and orlon posses this latent crimp. Man-made Figure 1.2 Natural 7

16 Natural and Man-Made Fibres Molecular arrangement It is about how the molecules in a fibre are joined together and the length of the molecule help to determine the property of a particular fibre. Fibres are made of long straight chain molecules called linear polymers. The arrangement of molecules resembles the arrangement of fibres in a yarn. The molecules may be parallel to the fibre axis or at right angles to the axis or spiral as they are in cotton and flax. This is called molecular orientation. Most of the fibres are parallel making the fibre crystalline. If the arrangement is not orderly than it is amorphous. When the man-made fibres are drawn from the spinneret the molecular structure is usually amorphous. Drawing and stretching aligns the molecules parallel to each other and also make the fibre more compact. It also henceforth reduces the diameter. When the linear molecules are packed together there is greater attraction between the hydrogen atoms of the chain. This is called hydrogen bonding. These bonds are weak cross-links but because they are so many of them they make the fibre stronger. Fibres which are highly oriented are stronger fibres e.g. Nylon. Figure 1.3 Chemical composition Cellulose fibres are poly hydroxyl alcohols. Protein fibres are composed of various amino acids. Acetates are polyesters of cellulose. 8

17 Textile Fibres Nylon fibres are polyamides. Polyester fibres are esters of dihydric alcohols. Acrylic fibres are addition polymers of acrylonitrile. Modacrylics are co-polymers of acrylonitrile and other substances. Nytril fibres are addition polymers of vinylidine dinitrile. Saran fibres are addition polymers of vinyl chloride. Vinal fibres are addition polymers of vinyl alcohol. Spandex fibres are elastomers composed of poly ureththane. Olefin fibres are addition polymers of ethylene, propylene or other olefin units. We can see that there are chemical differences in the molecular arrangement of fibres. These differences explain the reactivity of fibres, each different from the other. Fibre Properties Abrasion Resistance Abrasion resistance is the property of the fibre to withstand the rubbing or abrasion it gets in everyday usage. Inherent toughness, natural pliability and smooth filament surface are fibre characteristics that contribute to abrasion resistance. The following fibres are arranged in order of their resistance to abrasion: nylon, polyester, acrylic, wool, cotton, rayon, acetate. Strength The strength of a fibre is defined as the ability to resist strain and stresses and is expressed as tensile strength. Or as tenacity (grams per denier). Strong fibres have long molecular chains. Degree of polymerization is the term used to describe the length of the 9

18 Natural and Man-Made Fibres molecule chain. The D.P. of cotton is about 10,000 while that of regenerated cellulose is 300 to 500. Strong fibres are highly oriented while weak fibres contain large sections of amorphous area. Strong fibres make strong yarns. Thus, the fine strong fibred yarns may be used in the production of sheer fabrics extremely sheer nylon hose are possible because of the high strength of the fibre. Ramie, flax, nylon, dacron and vinyon are high tenacity fibres. While silk, cotton, zefran, dynel, creslan, orlon, saran are fibres which have medium tenacity. Rayon and wool are low in strength. Cohesiveness Cohesiveness is the ability of the fibres to cling together during spinning. This is an important property in staple but not in filament. Cohesiveness occurs because of natural crimp and unevenness in the fibre structure. Resiliency Resiliency is the property of the fibre or fabric to spring back to its original shape after it is stretched or deformed. This may happen over a period of time. A resilient fabric has good crease recovery, and hence requires no ironing. Resilient fabrics also retain high bulk and do not pack well when in use. This property enhances the beauty of the fabric and it is also easy to care fabric. All these properties of resiliency, elasticity, pliability and elongation are due partially because of the natural crimp in the fibre. All protein fibres have molecular crimp. Nylon has a folded molecular structure as it comes from the spinneret and it is cold drawn to retain some of the crimp. Cross-linkages and side chains help to explain these properties. Cross-linkages help to prevent the molecules from sliding over one another. Man-made, cotton and flax can be chemically cross-linked. 10

19 Textile Fibres This is on the basis of wash and wear finish. However, too many cross-linkages may affect the fibre adversely and it may become very harsh. Stability Stability is an important property a fibre must have for its easy care and upkeep. Stability is the retention of sizes. A stable fibre does not stretch, sag or shrink. Stable fibres make a stable fabric and a stable fabric can be converted into any useable apparel. Plasticity Plasticity is the property of a fibre to enable the user to shape it permanently or semi permanently by moisture, heat and pressure, or by heat and pressure alone. This property relates to the ease of beauty and care as well as the durability of the fibre. This is important from the consumer stand point. Wool has this property because of its scale structure and its lack of stability. Thermoplastic fibres are those which soften on heating. These fibres can be permanently shaped by heat. Thermoplastic fibres are all heat sensitive but vary in degree of sensitivity. They should not be washed in hot water. When the fibres are heated they either decompose or melt. Melting consists of separating the molecules. It is believed that cellulose fibres do not melt because of the large molecule size and because of the strong attraction forces of the hydroxyl groups. Protein fibres do not melt because of the presence of crosslinkages. Heating causes the molecule to vibrate with such force that they tear themselves apart or melt. Thus, we know how heat sensitivity affects production and care of fabrics. Comfort The properties of fabric which are associated with comfort are 11

20 Natural and Man-Made Fibres density, absorbency, hygroscopicity, and conductivity of electricity and heat. Absorbency Absorbency is the property of the fibre to take up moisture and is expressed in terms of moisture regain. This is the amount of moisture that a bone dry fibre will absorb from the air under standard conditions of temperature and moisture. Absorbent fibres make fabrics which are comfortable because they take up the perspiration readily. That is why they feel comfortable on hot and humid days. Absorbent fibres do not build up static electricity which also makes them more comfortable in dry, cold weather. Dry cold fibres are hydrophilic or water loving while non-absorbent ones are hydrophobic or water hating. Absorbency is an important property from the beauty point of view since they are easier to dye; absorbency is also related to resiliency. They tend to wrinkle more. Absorbency is due to the chemical structure of the fibre. This has many hydroxyl groups available, are very absorbent. Protein fibres which have many hydroxyl groups are very absorbent. Proteins fibres which have reactive amino (NH2) and (COOH) groups are very absorbent, highly oriented groups are not absorbent. Highly oriented groups are less absorbent than fibres with many amorphous areas. Since the water molecules get no space to penetrate. Wicking and wetting Wicking is that property which refers to conduction of moisture along the fibre or through the fibre. The fibre itself does not absorb the moisture. This property is related to surface wetting and nonabsorption of moisture by the fibre. 12

21 Textile Fibres Electrical conductivity This is related to the buildup of static electricity charges on the fibre. A good conductor does not build up static electricity charge. Heat conduction Heat conduction is largely a yarn or fabric property. Since fabrics are neither warm nor cool. However, because of the physical structure of the fibre they tend to make cool or warm clothing. Heat comes from the body if fabrics permit the body heat to escape like in cotton and flax they are cool fibres, if they do not permit body heat to escape they are warm fabrics for example wool. Beauty and hand Fibre properties related to beauty and hand are terms used to describe the fabric like soft, lofty, warm, silk like, and wool like are descriptive words which in other words is also known as hand. Loft Loft or compressenal resiliency refers to the ability of the fibre, yarn, or fabric to spring back to its original thickness after being compressed. In fibres loft is because of crimp. This property is good in sweater, blankets and shawls. Cover Fibres with irregular cross-section and with crimp curl or twist to give better cover for protection purposes. Cover means concealment or protection on the surface. Body The overall look or rigidly firm appearance of the fibre may be termed to be the body of the fibre. 13

22 Natural and Man-Made Fibres Drape The manner in which the cloth hangs is called the drape of the fabric. It may be soft and limp, or stiff, and buoyant. Fabrics which have a nice fall on the body are said to have a good drape, and for example silk has a good drape. It falls on the body with very elegant lines. Lustre Lustre is light reflected from the surface. It differs from shine in that it is more subdued since the light rays reflecting on the surface are broken up. Smooth flat fibre reflects more light than round or rough fibres. Fibres with many striations have high lustre, for example Rayon. Yarns of long fibres which are laid together with little or no twist reflect more light than yarns with shorter length. Manufactured fibres are delustred to make them close to look natural. Oil or pigment is added to the solution before it is extruded out of the spinneret. Lustre Shine Figure 1.4 Colour Affinity to take and hold colour is largely contributed to the chemical composition of the fibre. Absorbent fibres take dye more readily than non-absorbent ones. 14

23 Textile Fibres Chemical resistance The chemical reactivity of each fibre depends on the arrangement of the molecules it contains. Dry-cleaning solvents, perspiration, soap, synthetic detergents, bleaches, atmospheric gases, soot, and sunshine may all cause chemical degradation on some or all of the fibres. Alkali strengthens the cotton fibre. Alkali and chlorine may be used to make wool shrink resistant. Scientifically controlled use of chemicals brings about beneficial mordants and finishes. Resistance to moth and mildew Fibres without natural resistance should have protective finishes to prevent moth and mildew. Also, often it is due to the chemical composition of the fibre. These properties enhance the usage of protected fabric for clothing. Flammability Flammability depends upon the air incorporated in the fibre. Combustible finishes and dyes make the fibre flammable. Anti flammable dyes must be used to protect the fibre and make it nonflammable. Elasticity Elasticity is the property of any stretched fibre to return to its normal shape soon as it is out of use. e.g. socks. Pliability of flexibility Pliability refers to the fibre to softly fold in any possible direction. It is because each fibre has the ability to fold that it can be converted into a three-dimensional outfit. They are easy to twist in to yarns. 15

24 Natural and Man-Made Fibres Stiffness and rigidity This property is just the opposite of pliability. Rigidity is important to any fibre because it determines the insertion of any twist to the fibre. Elongation Elongation is the deformation caused due to stretching. It is expressed as percentage of original length. For example if a fabric is 100 cm and it can be stretched to 110 cm before it breaks then its elongation is 10 percent. 10 percent elongation is desirable. Elongation varies at different temperatures it is different when wet and when it is dry. The table below shows the elongation of certain fibres under standard condition. Dry fibre Percent elongation Wool 25 to 35 Acrilan 35 Dynel 39 Vycron 31 to 35 Creslan 32 Fortel 3o to 35 Nylon 26 to 32 Nylon staple 16 to 42 Rayon 15 to 30 Silk 20 Acetate 25 Cotton 5 to 9 Flax 6 to 7 Glass 2 Avril 5 to 9 Dacron 16 to 42 16

25 Textile Fibres Classification of Textile Fibres Fibres may be broadly classified into 3 groups: a. Natural fibres. b. Man-made fibres (non-thermoplastic). c. Man-made fibres (thermoplastic). Figure

26 Natural and Man-Made Fibres Figure

27 Textile Fibres Nature is abounded with different kinds of fibrous materials. Man has learnt to extract and synthesize fibres from available natural resources and also chemicals. The fibre which is the basic single unit out of which all fabrics are prepared, has properties which are inherent to the material from which it has been extracted. Some such properties are length, strength, pliability, diameter, abrasion resistance and nature of the surface area. Along with all these properties the fibre must be pleasant to the touch both as to texture and temperature, absorbent to some extent so that they can be dyed and be comfortable to wear; can be cleaned, they should be light weight if used for apparel, resilient, durable and available at an affordable price. No fibre is perfect. All of them are lacking in a few or many of these characteristics. Modern production methods have overcome some of the difficulties in making fibres into fabrics. Blending is done to impart properties of two different fibres to produce a good yarn for a fabric. All fibres, whether natural or man-made are chemically known as polymers. Polymers are the result of a process called polymerisation. It is defined in Hackh s dictionary as a reaction in which two or more molecules of the same substance combine to form a compound the new molecular weight being a multiple of that of the original compound [monomer] or the structural arrangement in which two or more different monomers or types of groups are present in alternate sequence in a chain [copolymer]. In simple polymerisation, units (molecules) of the same compound combine to form the long chain. In hetropolymerisation, polymerisation occurs between two different kinds of units, only one of which is capable of polymerisation by itself. A simple compound A and another simple compound B can form a long chain of polymer A A A A A A A 19

28 Natural and Man-Made Fibres or make a series of B B B B B B B Both of these are simple polymers. But if we can, in some way, make units of A combine with B into a molecular chain, we have a copolymer A B A B A B A B If we introduce a compound, C, which we cannot make polymerisation happen by itself, it can cause it to combine in a chain with either A or B or with both, we have a hetropolymer, e.g. A A A C A A A C A A A The natural fibres are simple polymers (cotton, linen) or copolymers (wool, silk) and among the man-made fibres may be found all three types of polymers. This explanation helps to understand the complex nature of textile fibres in a simple way. 20

29 Chapter 2: Cellulosic Fibre - Cotton I ndia was the first country to manufacture cotton. Among the latest finds at Mohenjo-Daro were a few scraps of cotton were found sticking to the silver vase. This shows that cotton had been produced in India as far back as even the fourth millennium B.C. Historians speak of the beautiful painted and printed cloth which was sold in Egypt and some parts of Europe long before the time of Alexander. Figure 2.1 It is generally accepted that wool first came into use and cotton came later. It is not known when India first started to trade with Europe, but the word Carbasina (Sanskrit word Karpasa) for cotton suggests that it must have been in use before 200 B.C. To the Greeks who came to India with Alexander India was a land of mystery. They were so surprised to see cotton that they called it

30 Natural and Man-Made Fibres wool produced in nuts. They wrote wild trees in India bear fleeces in their fruits, surpassing those of sheep in beauty and excellence. Properties of cotton Cotton is the seed hair of the shrub which bears the botanical name of Gossypium, a member of the mallow family. The shrub grows to 6 feet tall height. From 80 to 110 days after planting the plant bears beautiful creamy white blossoms, which turn pink and fall off and are replaced by a green triangular pod called boll. The fibre develops within the boll. The boll is the size of a walnut. The mature boll bursts open from the fibre pressure, exposing the fluffy mass of white cotton fibres. Cotton is classified according to fibre length, fineness, lustre and geographical location. Figure 2.2 After cotton is picked several steps are necessary before it can be spun into yarn, like ginning, baling, grading marketing, opening, picking, carding, combing, drawing, roving, spinning winding and spinning and twisting. 22

31 Cellulosic Fibre - Cotton Figure 2.3 Ginning: Ginning is the process by which seeds are removed. Several ginning machines have been designed. Shown in figure is a ginning machine. Roller gins are used for long-fibre cottons and saw gins are used for intermediate and short fibre cottons. Eli Whitney, is famed for the invention of cotton gin, an invention of great importance in the development of cotton industry. A ginning process, carried out at the seed crushing mills removes the linters. Baling: After ginning the cotton is compressed into bales, usually square in shape, the bales are covered with burlap to protect the fibre and are banded with steel bands to keep the bale in shape and to make it manageable for handling. Bales vary in weight from 250 lb to 500 lb for square bales. Grading: Quality of cotton according to staple, microns colour and foreign whiteness and spottiness. Grading determines the quality rating of cotton and the price. It will bring to the market in relation to the price of standard grades in that particular season. 23

32 Natural and Man-Made Fibres Grading is done bale by bale. Grade is based on colour, foreign matter and preparation. Degree of whiteness, spottiness and other discolourations of various types affect the colour rating. There are six colour variations for upland cotton grey, extra white, white, spotted, tinged, and yellow stained. Foreign matter consists of broken leaves, bits of twigs, sand and dust. Preparation refers to the quality of ginning, whether fibres have been cut, tangled, bunched etc. and is designated as A, B, C. The classes for grading of cotton from best to poorest are middling fair, strict good middling, middling, low middling. Staple: An average staple length is determined from three properties. The average length, character which includes strength, maturity and fineness. The effect of these qualities on texture and properties of fabric and in converting fibres to yarn. The average length is very important to the manufacturer in making the necessary adjustment to his machinery. Character: Character of cotton includes strength, fibre maturity, fineness, spirality, convolutions, ability of the fibre to cling together and body (softness, harshness, hardness). Marketing: Marketing includes all transactions from the time the cotton leaves the producer until it is accepted at the mill. Some cotton is sold directly from producer to mill, but most of it goes through a series of selling operations. Most cotton is actually handled often in bales of 100 of the same grade around the cotton markets of world. The largest being New York, Liverpool, New Orleans, Memphis and Houston. In India, cotton is produced in Orissa, Maharashtra, some places in Punjab. Many of the series of marketing steps are the small markets or in the cotton exchanges. The spot markets are the small markets dotted through the cotton producing areas and cotton mill areas of the country where the cotton farmer sell their cotton to small merchants or to 24

33 Cellulosic Fibre - Cotton cooperatives. The cotton sale is an organization something like the stock exchange, deals only in futures market with no actual cotton bales and sometimes no samples of cotton are present. But future sales made on the basis and grading. Properties Microscopic Cotton fibres have twisted flattened appearance much like a twisted ribbon. As it grows the fibre develops a primary and a secondary wall. The centre part is the lumen. The Lumen carries liquid to the living cell. When the boll opens the liquid dries up rapidly causing the lumen to collapse. The fibre then assumes the characteristic twisted or spiral form. Long fibre cottons have more twists per unit length than other cottons and mercerised cottons of all types often show fewer twists than the unmercerised cotton. Chemical properties The chemical composition of typical cotton is 94% cellulose, 1.3% protein and 0.9% other things including sugars. The cellulosic content of raw cotton varies Figure 2.4 from 88% to 96% depending on the variety of cotton soil and growing condition. Cotton fibres are very absorbent. This accounts for their comfortableness, especially in hot climate. In the process of absorbing the fibres tend to swell considerably in cross-section area. Their length is little affected. This fact is utilized in some of 25

34 Natural and Man-Made Fibres the finishing processes. Cotton is decomposed by strong acids hot or cold and is deteriorated by weak, hot acids. Strong sulphuric acid is used for parchmentizing by the Haberlein process. Permanent organdy finish is given by this process. Fabric is dipped in sulphuric acid for a momentary treatment. Figure 2.5 Internal structure of cotton The cotton fibre which are visible to the naked eye, when viewed under high magnification as with electron microscope are shown to be comprised of many layers of tiny fibrils arranged in definite spiral pattern with the different layers at right angles to each other. This structure as the fibre ripens may account to the twisting of the fibre as it dries. The picture shows the layered structure of cotton fibre as revealed by the microscope after staining and swelling treatment. 26 Figure 2.6

35 Cellulosic Fibre - Cotton Mercerisation Mercerisation is a process which was discovered by John Mercer in 1853, a calico printer. Mercerisation is accomplished by dipping the fabric in 18 to 23% solution of caustic soda for one half to two minutes at room temperature with the cloth held under tension. Mercerised cotton has increased lustre and increased strength. The fibre becomes more cylindrical. Mercerised cotton is stronger, has increased affinity to dyes so that less dye is needed, dyes more evenly has greater affinity for resins and other finishing compounds and is more sheer in appearance. It soils less easily than unmercerised cotton. Physical properties of cotton Cotton fibres are most often creamy white in colour, although the colour varies with variety, type of soil in which it is grown and the climate. Rain and dust on the open boll stain the fibre. Egyptian cotton has a reddish brown cast and is darker in colour than the Sea Island upland cotton. Usable cotton fibres of different variety vary in length from 0.5 to 2.5 inches, and in diameter from 6 to 26 microns, with specific gravity of 1.50 to Cotton is thus one of the shorter fibres intermediate in width and its density is higher than most of the other fibres. Cotton has medium tensile strength compared to other fibres, but when wet its strength increases as much as 30%. The increase in strength is very important when working in tropical or very humid climates where moisture and perspiration are likely factors that must be taken into consideration. Cotton has medium abrasion resistance and high flex resistance. Cottons low resiliency means that cotton fabric will wrinkle and that wrinkles will not straighten out but will require ironing for removal. Cotton may be stored for long periods with no 27

36 Natural and Man-Made Fibres apparent loss of strength and this also may cause yellowing. Prolonged exposure to sunlight causes great loss of strength. Cotton scorches if ironed with very hot iron. This causes damage and loss of strength. Cotton is readily refreshed by washing and ironing. It is considered to be the least expensive fibre in terms of upkeep, because cotton without damaging the fibre can be sterilized in boiling water or in a steam autoclave it is usually considered to be the most antiseptic of all fibres. It is widely used in hospitals for operating room materials and uniforms also for the fact that cotton presents no problem of dangerous accumulation of static electricity. Biological properties Under conditions of high humidity mildew, bacteria, yeast will grow on cotton. Starched cotton is more likely to be attacked than unstarched cotton. This attack weakens the fibre and also leaves behind a disagreeable odour. Silverfish and termites also attack cotton. Cotton fabrics may be treated to protect them from attacks by microorganisms, but the treatment may change the appearance and texture of the fabric so much that its uses are limited. These treatments are important for outdoor fabrics such as lawn tents, lawn furniture, and camp furnishing where appearance is not as important as end usage. Major cash crop Cotton is the major cash crop of India with the death of antidumping regulations. India expects a substantial increase in its textile trade. Caught in the spinning wheel are the 3 countries US, China and India. The biggest problem is that U.S. The United States gives big subsidies to its cotton farmers. So India is importing cheap raw cotton. The strange thing is that while India is now importing raw cotton it is also exporting, mainly to Bangladesh and China - through a private procurement and export 28

37 Cellulosic Fibre - Cotton regime, due to which the local farmer is affected. More than 70 countries globally produce and export cotton. Of these eight countries are responsible for almost 80% of global output. The world s cotton market is dominated by the U.S. which is the second largest producer after China. Despite these reasons India started exporting cotton in In 2005, India exported 800,000 bales. Export from India is increasing. The cotton exported from India is middling staple. It is of a very ordinary quality. Cotton farming in India (SWOT analysis) Cotton plants grow almost all over India. Black cotton soil of south India is the best soil for growing cotton. Part of Orissa, some places in Gujarat, Punjab and Haryana seem to be favourable. Cotton requires a humid climate and a rainfall of 12 to 15 cm. Approximately 700 kg/hectare cotton is produced all over the world. America, Australia and Brazil produce about 1200 kg/hectare. The per hectare yield of India is 300 kg/hectare. Although cotton is an important cash crop of our country but the reason for this low productivity are many. Poor agricultural processing. Dependence of farming on rain water. Poor irrigation facility. Poor ginning. Although large land mass of India about 9.5 million acres is used for the cultivation of this cash crop, it also guzzles a lot of water. One cotton plant needs 700 to 1300 mm water depending on the growing period in the early stages. Only 35% of the area is irrigated rest is rain fed. Due to poor farming facility the produce is of a very inferior quality. Cotton exported from India is medium staple cotton, which is a below average variety of cotton. 29

38 Natural and Man-Made Fibres Uses Cotton plant in Indian tradition is much more than the source of raw material for textile above. Cotton flowers give us nectar and if bee keeping is planned, it gives highly flavoured healthy and tasty honey. Cotton seed oil is a well-known edible oil. It is also used in Vanaspati formulations. In Ayurveda, equal quantity of ginger is used for external application to relieve pains due to rheumatism and arthritis. Roots of cotton plants are used for female diseases. Leaves are good for green manuring. Oil cake is a cattle feed and a good raw material for industrial adhesive besides being a good manure. Figure 2.7. General steps in manufacturing cotton textile goods. 30

39 Chapter 3: Linen (Flax) - Cellulosic Fibre I t is known that linen was produced in Egypt long ago to be a developed art by 3400 B.C. A robe of this fabric is said, could be drawn through a small finger ring. From ancient Egypt, with the rise of sea travel and trade the use of linen spread around the Mediterranean Sea. In due time France, Belgium and Holland became famous for the quality of the linen produced. Ireland became predominant. The Irish climate is ideal for the spinning and weaving of linen as dampness keeps the fibre tough rather than brittle. Figure 3.1 Botanical name of linen is linum usitatissimum, a name indicative of its many early uses. The term flax is derived from Anglo Saxon and old high German words. Linen designates both plant and fibre. Flax is a slender straight stemmed plant with narrow, medium green lance like leaves which grow to a height of

40 Natural and Man-Made Fibres 2 to 4 feet. The longest stemmed varieties are planted for fibre. The plant branches near the top into few branches, which in turn bear the half inch wide blossom and the seed boll. The different varieties may be coloured pink, purple, white or azure blue. The white and the blue are of commercial importance. Blue flowered flax is considered to have better spinning qualities than white. Flax grows in a temperate climate under a wide variety of climatic conditions but does best with cool, even temperature and considerable rain fall, it requires a growing season of 85 days to 100 days. The height of the plant, the fibre length and the quality of the fibre varies greatly with soil and climatic conditions. Flax does not require a rich soil the seedbed must be carefully prepared. Once planted no special care is required except to keep the weeds down. While the plants are young, flax is subject to some rather severe plant diseases. So it is usually rotated from field to field rather than grown in the same field year after year. Flax fibres occur in bundles just inside the relatively stiff cuticle outer wall and surrounding the woody central part of the stem. The fibres are bound together within the bundles by a cellular tissue sometimes called the phloem and by gums and waxes. These substances are largely removed during processing allowing the individual flax fibres to be separated. Formerly flax cultivation was almost entirely a series of hand operation but now, as in other agricultural endeavours it is becoming more mechanized. The stage at which flax is harvested depends on the end product desired. Flax for seed is harvested when stems and seed bolls are quite dry and are yellowish brown in colour but still moist and supple. 32

41 Linen (Flax) - Cellulosic Fibre Processing Flax stem is then put to pulling, retting and scutching. Pulling: Pulling is the removal of the whole plant including the root system from the soil. Unbroken stems are required for maximum fibre length and also to prevent staining of the fibres within the stem during the drying and retting processes. This is also now a mechanized procedure. Retting: Retting is a process by which the brittle outer cuticle layer of the stem is broken down and at least partially destroyed by fermentation through bacterial action and by moisture allowing the fibre groups to be removed. There are several methods of retting all of them slimy odorous and unpleasant, making this a most disagreeable process of flax production. Removing the cuticle by chemical treatment is called chemical retting but the fibre extracted is of a poor quality. Dew retting: This is a slower process than other processes. Since it is slower than other processes it takes 2 to 3 weeks. Water for retting must be clean and free from minerals. Especially iron that Figure 3.2 might discolour or damage the fibre and it should preferably be soft water. During retting the water penetrates to the inner parts of the stalk via small flaws in the cuticle or bark causing the inner cells to swell and burst the cuticle. This in turn increases moisture absorption and permits greater penetration of bacteria which act 33

42 Natural and Man-Made Fibres upon pectin s, the substances surrounding the fibre bundles, changing them into soluble sugars. Running and stagnant water retting are carried out in similar fashion. The flax bundles are placed in crates that are weighed down with stone to keep the entire length of the stem submerged in water after bacterial action commences and gases form. Tank retting: This is another form of retting, which is carried on in specially built tanks. Constant lukewarm water temperature is maintained. In tanks, fermentation can be closely controlled by maintaining the ph of water. The water penetrates to the inner part of the stalk via small flaws in the cuticle or bark causing the inner cells to burst and swell. This in turn increases moisture absorption and permits greater penetration of bacteria which act on pectins surrounding the fibre bundles. After retting the fibre bundles are dried with drier. Decortication: Although decortication is a process of scraping the cuticle and woody centre it is also used for substitute retting. Scutching: Scutching is the process of removing the dried retted fibre from the woody remainder of the plant stem. The first step is the breaking operation in which the butted parallel stems are passed through a series of fluted rollers, which break up woody portion of the straw into fine pieces called shives which can Figure

43 Linen (Flax) - Cellulosic Fibre be beaten out and which leave the long linen fibres largely undamaged. The resulting long fibres are called line or flax. Flax fibre has been designated by five grades according to fibre length and colour, general conditions and lustre. A good quality spinning fibre is fine soft strong and has a somewhat cold and oily feel and a glossy sheen. The fibre is strong, absorbs moisture and has good wicking ability. When blended with cotton it makes an excellent fabric for summer wear. Properties Physical properties It is the strongest of all vegetable fibres. It is stronger wet than dry. Colour of linen varies from a creamy white to brown, the depth of colour largely depending on time and condition of retting. It may be bleached to white. Linen fibre varies from 12 to 30 inches in length and 5 to 28 microns in diameter. Linen has low elongation and resilience. Ironing when quite damp is necessary to restore its freshness. It crushes and wrinkles readily unless treated for crease resistance. It becomes softer and more lustrous with frequent laundering. Because of its strength linen is a very durable fibre. Untreated linen feels cool to the touch and is one of the most absorbent fibres owing to its wicking ability. It absorbs rapidly and is quick Figure 3.4 to dry. It is one of the most comfortable fabrics for warm climates. Linen is sometimes considered to be an expensive fabric, but today it is competitive in price with many other fabrics. Its durability should be taken into account when considering its cost. 35

44 Natural and Man-Made Fibres Linen fabrics can be flattened and made more lustrous and soft during manufacture by a beating process called beetling, in which the fabric is pounded with hundreds of tiny hammers. This process does not harm the fibre, but destroys part of the cementing substance between the fibres and gives it more sheen and smoothness by reducing the space between the weave. Linen is being blended with cotton to make the blue denim jean more comfortable the good qualities of linen e.g. absorbency and also its property of wicking have rendered significant boost to blending cotton and linen to make jeans comfortable in summer. Linen can be distinguished from other commonly used textile fibres by its distinctive appearance. As seen in cross- sections the fibres are round to polygonal usually five sided with rather rounded corners. Linen has a natural lustre it does not need mercerisation. It can be satisfactorily bleached or treated with a resin for crease resistance and other properties. It is the strongest of all vegetable fibres. Linen is a very durable fibre because of its strength and good quality. It is readily refreshed on ironing. Microscopic structure When viewed through microscope linen can be distinguished from other commonly used textile of bamboo or various types of cane, because of transverse lines or nodes, a characteristic of most of the bast fibres. Immature fibres are oval in shape with much larger lumen. Raw flax Figure

45 Linen (Flax) - Cellulosic Fibre fibres are composed of about 71.5% cellulose, 10.7% water, 9.4% gums, pectin etc. 6.0% extract, 2.4% fat and waxes, and 1.3% ash. When boiled off and bleached linen becomes pure cellulose. Linen may be attacked by mildew, resin finishes tend to cut down on the likelihood of microorganism attack on both linen and cotton. Uses and by-products It is largely used as apparel, ladies blouses, shoes, handbags, hats, textile furnishing which include drapery and upholstery fabrics, towels and damask and other napery and rug. Industrial uses include sewing threads for leather goods. Linen has long been in use for fire hose because of its great strength, low elasticity and quick absorption of water, so that it becomes wet quickly and can be handled comfortably (temperature wise) and is not likely to catch fire as long as water is going through it. By products of linen are from the seeds. The most important by product is linseed oil. This is a valuable oxidizing (thus drying) ingredient in many outdoor paints. Flax seed is an important ingredient in some medicines and drugs. 37

46

47 Chapter 4: Minor Cellulosic Fibres H arris in the handbook of textile fibres has listed 8 seed and fruit hair fibres, 38 bast fibres and 40 leaf fibres and a great many additional miscellaneous vegetable fibres. There are several bast fibres of considerable commercial importance. They are called soft fibres. In this group we shall consider jute, kenaf, hemp, ramie, sunn, milkweed, kapok. Among the leaf fibres often called the hard fibres we shall consider abaca, pina, sisal, henequen. Bast The bast fibres are plants tall slender growing to a height of 5 feet to 16 feet, with stalk ½ to ¾ inch in diameter. Height varies for different plants with geographical area, soil, climate, and conditions of growing season. The plants have relatively few leaves, which are borne near the top. The fibre grows inside the cuticle of the stem as does linen in the flax plant. The individual fibres are short but because cementing substance is not removed, the fibres overlap and may be removed and used as long continuous strands, limited only by the lengths of the stems. Properties common to all are not repeated in the following chapters on minor cellulosic fibres. Jute Jute ranks next to cotton in the amount of fibre produced in the world and in commercial value. It is the world s most plentiful,

48 Natural and Man-Made Fibres cheapest and weakest fibres. Jute is grown mainly in Pakistan, India and Brazil. Before partition of India, India produced almost all the supply of jute. Microscopic structure of jute resembles that of flax, but it usually lacks the cross markings characteristics of bast fibres. Raw Jute is 60 to 64% cellulose, with a high lignin content which accounts for the woody nature of the fibre. Jute is hand cut, the fibre is removed by retting and stripping from the remainder of the Figure 4.1 deteriorated stalk tissue by one of four hand methods. Then it is washed repeatedly to remove bits of bark, gum etc. and dried in the shade. Sunlight weakens the fibre. The colour and quality of the fibre depend considerably on the degree of maturation of the plant when harvested. Jute is a week fibre, it is harsh brittle with low elongation and little elasticity. Colour is from creamy white to dark brown. It has considerable lustre, darkens and weakens with exposure to light. When it is humid it is easily attacked by moth and midew. Jute is weaker when wet than dry. Jute is relatively a cheaper fibre so it is used for Figure 4.2 bagging and wrapping fabrics. Much fibre is used for rope twine, cord, and backing for carpet and rugs. Recent uses in hand purses and apparel have given the fabric a boost. Burlap is the fabric made from jute. It has many uses: it is used as under covering for upholstered furniture for bulletin 40

49 Minor Cellulosic Fibres boards, slip, covers. It has limited use in apparel. Recent researches have blended jute with cotton to bring it into apparel use, and also in home furnishing. Hemp Hemp is a bast fibre from the Cannabis sativa family from the Moracea family. But the name is also applied to number of other plants. Hemp is an important crop in Italy these days. Figure 4.3 The production and manufacture is similar to flax. It matures in 90 to 120 days, with the male plant maturing one or two weeks earlier than the female plant. Male and female plants must be harvested at the same time by mechanical methods and often by hand method. Hemp grows best on moderately rich sandy loam, and needs considerable rain fall, 3 inches per month. It may be produced for seed oil. Italian hemp is about 78% cellulose. Colour of hemp varies from creamy to yellow, grey, greenish or brown depending on quality and methods used in harvesting. The largest use of hemp is in cordage. Sunn Sunn is the fibre from Crotalia Junacea plant of leguminosie family. Sunn requires a growing period of 100 to 110 days. The 41

50 Natural and Man-Made Fibres plants have been grown for fibre since prehistoric times in India and Pakistan. The fibre is more difficult to handle than jute, because it rots very quickly after retting is complete. It is used as fish net, twins, rug yarn and in paper making. Mathews Textile Fibres (p. 324) says lack of care in fibre preparation has perhaps been one of the factors deterring wider use of the fibre. Figure 4.4 Ramie Ramie is plant commonly known as china grass, grass linen, grass cloth and rhea, is a bast fibre from the Boehmeria nivea of the Urticaceae family. Ramie is a fibre which has the greatest potentiality of all the Figure 4.5 minor cellulosic fibres for apparel and furnishing, but numerous difficulties remain to be overcome. Ramie grows best in a warm moist climate, with temperatures ranging from temperate to subtropical. Rich well drained soil is preferred. Strong winds cause the stalks to rub against each other, damaging the fibre. Fibre is removed from the stalk by decortication; it is dried in sun and air. It is then degummed in which process it is boiled in a chemical solution usually made with caustic soda. After degumming the fibre is 42

51 Minor Cellulosic Fibres rinsed, neutralized, washed and dried. One plant will produce stalks over an area of 16 to 20 square feet. Ramie fibre is lustrous and has high strength. It is white in colour. Ramie is said to have exceptionally high resistance to bacteria, fungus and mildew. Decorticated ramie is 83% cellulose and when properly degummed it may be 96% cellulose with little or no lignin. Ramie can be used wherever linen is used, for clothing, upholstery, fabrics and home furnishing. It is also used for fishnets, cords, sewing threads, canvas, packaging, fire hose, and filter cloth. The shorter waste fibres are used for making paper. Abaca 95% of the world s supply of abaca is from Philippines. For many years the efforts to grow abaca in other parts of the world failed. Abaca is called Manila hemp. Abaca is the species of Musa plant family Figure 4.6 to which the familiar commercial banana belongs. The importance of this group of plants to the economy of their country has been described by B. Montgommery in Mathews book of Textile Fibres (p. 361). Plants of the genus Musa of which there are a large number of species, are among the world s most useful plants. They furnish an important proportion of the world s supply of cordage fibres as well as fibres for coarse and some fine fibres. The fruits are important in the diet of the people of many countries, in some countries the 43

52 Natural and Man-Made Fibres flowering bud is eaten as a vegetable. And the leaves are used as lining for cooking vessels. The juice of the plant is used as dyestuff. By the people of some countries and the leaves are used as lining the cooking vessels and wrapping food and other articles sold in shops, for polishing floors, and as both rain and sun umbrellas. Abaca fibre is of good quality strong, lustrous and varies in colour from white through browns, red, purple, depending on variety. Fibre strands vary from 3 feet to 6 feet in length. Its elongation is higher than most of the bast fibres. Of special significance to marine users that abaca is quite buoyant and that it has an unusually high resistance to the effect of salt water microorganisms. Abaca is the most extensive export crop. The propagating roots are continuously sending out new shoots. Abaca is the only leaf sheath fibre of commercial importance. The Abaca plant grows to a height of 15 to 25 ft, in clusters of 12 to 30 stalks to a mat. Abaca requires well drained moderately rich soil and a subtropical climate with considerable sunlight, heavy rainfall evenly distributed throughout the year and a general absence of strong winds because the shallow root system allow the plant to topple very easily. Uses Abaca is mostly used for ropes and cordage of various kinds, for packaging material and for fishing and cargo nets. It is used for braids of hats, slippers and handbags. It is also used for hats, rugs, curtains screens in paper auto seats and furniture. Coir Coir is derived from commercial coconut. It is the outer husk surrounding the nut. Coconut husks are split with knives and the 44

53 Minor Cellulosic Fibres ripe nuts removed from the woody portion of the husk by pounding and hackling and by a breaking process similar to that used for bast fibres and a stripping process against spikes on a rotating drum. Coir is hard, tough, brown in colour 4 inches to 10 inches long and quite coarse in diameter. The longer fibres are made into yarns for cordage, fishnets and coarse cloth. Short and broken fibres are baled for use as mattress fibres and upholstery stuffing. Coir fibre has a natural affinity towards dye stuffs. Coir being a vegetable fibre shows more sensitivity towards basic colours. Basic colours are not stable to sunlight. Even then they can be applied to indoor mats and upholstery material which is not exposed to sun light. Coir belongs to the group of minor cellulosic fibre. Sisal Sisal is obtained from the plant Agave sisalana, a member of the family amaryllidaceae. It is native to Mexico. Chief sisal producing countries are Tanzania, Brazil, Kenya, Haiti, Angola, Mozambique and Indonesia. The long narrow, stiff leaves of the sisal grow out as a rosette from a very short thick stem. The leaves are 4 to 6 ft long and 4 to 7 inches across at the widest part, and are concave enough to Figure 4.7 have a horse shoe shape. Plants are propagated from rhizomes or from bulbils tiny plants that develop from buds in the axils of the flower stems as the blossom whither and the old plant dies. 45

54 Natural and Man-Made Fibres Leaves must be cut when ready decorticated, washed and dried at once to remove the gum which would otherwise harden and prevent proper preparation of the fibre. Sisal strands of good quality fibre average 40 to 50 inches length and 0.08 to 0.15 inch diameter. The fibres are white, lustrous somewhat less strong than abaca, somewhat stiff, and show resistance to salt water microorganisms. Sisal absorbs moisture very rapidly. Sisal ropes sink more rapidly than abaca ropes. It is 66% to 72 % cellulose. Uses It is used for ropes, hats, cordage, handbags, shoes of good quality, white fibre. Henequen It is derived from the leaf of Agave fourcroydes, where it has been used since prehistoric times. Mexico is the leading producer of henequen, with Cuba being the next. Henequen leaves like sisal grow as a rosette from a thick central stem and there is a close parallel to sisal in the age and manner of harvesting. The steps involved in preparing the fibre and in appearance and structure of the strands. Henequen however has only fair strength and elongation, compared to sisal, nor does it have good resistance to salt water microorganisms. Uses It is used for ropes, tying and wrapping twines, bagging, hammocks, shoe soles and a number of other items. Milkweed Often called floss for its silky appearance and feel, is obtained from the plant of Asclepias syriaca or its relative of the 46

55 Minor Cellulosic Fibres Asclepsidaceae family. These familiar plants grow wild throughout America and many areas of the world, or they may be cultivated. Their potential value of soil conservation plant is very high. The fibre to which seed is attached is tightly packed into cylindrical green seed pods that burst open when ripe, scattering the tiny seeds over a wide area because of the parachute like propulsions of the attached fibre. During World War II many children patriotically collected milkweed pods for the government as the fibre in great demand for life belts and life Figure 4.8 jackets for the armed services on all kinds of sea duty and for service personnel being transported by water. The supply of kapok which was earlier being used for their purpose was cut off during hostilities. The milkweed fibre in the jackets linning served a double purpose, to provide insulative warmth onboard ship or to keep the wearer afloat if forced in water. Each fibre is a single smooth cylindrical air filled (thus buoyant) hollow rod with a somewhat distended base. It is very light in weight, to inch in diameter, very lustrous white to yellowish white in colour and moisture and vermin resistant. Because of the nature of its fibre and its buoyancy it does not lend itself to spinning and weaving. According to test data of a few years from the Department of Health of the State of Maryland, a sample of milkweed fibres floated in hydrant water for 41 days with 30 times its own weight attached. Another sample floated for 44 days with 33 times its 47

56 Natural and Man-Made Fibres weight attached. When the second sample was dried and reimmersed it floated for 30 days. Kapok Kapok is derived from the seed pod of the tree Cieba pentranda of the Bombaceae family of plants, which grows to a height of about 100 feet and starts producing harvestable pods when 5 to 7 years old. Its productive life is 50 years or sometimes even more. Fibre is obtained from either India or Java, although the latter is preferred. Compressed java kapok is said to be able to support up to 36 times its weight and Indian kapok 10 to 15 times its own weight. The ripe pod is tan in colour, similar to a milkweed pod in appearance. The pods are picked from the trees and just before they are ripe enough to burst open, scattering the fibre. They are cut open, the seed and the fibre separated by hand and the fibre sun dried inside wire netting to prevent it from blowing away. The fibres of mature kapok do not cling to the seed as do cotton and milkweed fibres to their seed. The descriptions of the fibre are almost the same as for milkweed, except that its fibre is somewhat shorter and finer in colour. Kapok is very resilient, a mattress 3 by 6½ requires only 17 lbs of kapok as compared to 30 to 60 lbs of straw. Further, it does not retain moisture which is very important in moist climate. Urena Urena is derived from the bast fibre from the plant Urena Lobata of the malvaceae family. The family to which kenaf also belongs. Mathews Textile Fibres book says: Urena grows wild sometimes becoming a noxious weed, in tropical and temperate zones in South and North America, Asia, Indonesia and Philippines, Madagascar and to a much larger 48

57 Minor Cellulosic Fibres extent in the Belgian Congo and in French equatorial Africa. The use of urena fibre in Belgium is of great antiquity. The principal producing areas being Espirito Santo, which accounts for about three fourths of the total, and Para, Rio de Janeiro and Sao Paulo. The use of urena fibre in most of the other areas where the plant grows also covers a long period of time. The first attempt to cultivate the fibre also met with no Figure 4.9 success. A second attempt was made in 1929 by a Belgium textile firm, in the province of Leopoldville and proved to be very successful. Urena grows best in hot and humid climate, on soil with adequate potash content, away from shade and where water will not stand on its roots. It matures in 120 to 150 days and is harvested when in full bloom (pink flowers) by about the same method as jute, except that the stalk must be cut a distance above the ground because of the high degree of lignification of the base of the stalk. Retting generally takes 9 to 12 days for urena. Urena is creamy white, lustrous, fine soft and flexible. Strands of fibre are 3 feet or more in length and almost as strong as jute it has the same uses as jute or other fibres. Experimenting in growing, harvesting and grading urena have been carried on in different countries and have been in Belgian Congo. Urena can prove to be a good fibre provided quality can be standardised. 49

58

59 Chapter 5: Wool - The Protein Fibre W ool is the first fibre that man learnt to make into fabric, either by felting or matting. Wool is the hair or fur covering of the sheep. Originally, sheep had two coats a coarse protective wiry coat and a soft warm fleecy undercoat of very fine texture. History clearly shows that Mesopotamia was the birthplace of wool. The early Romans encouraged sheep farming and wool weaving in England in A.D. 80. Soon the British woollen clothes gained reputation. Woollen Kashmiri shawls are as old as the epics of India. Tradition has it when Lord Krishna went to Kurus as a delegate from the Pandavas, the presents of Dhritrashtra to him were ten thousand shawls of Kashmir. Figure 5.1 Martin wrote the gossamer muslin of Dacca and beautiful shawls of Kashmir adored the proudest beauty of the court of

60 Natural and Man-Made Fibres Caesar. In ancient India, cotton was not known to the Vedic people, but wool was an important material. Fine wool was obtained from places near Gandhar and the region in which the river Ravi (the tributary of river Indus) flowed. The Abhiras brought woollen clothes of various designs manufactured in Cina and Valhika which were the provinces between Sutlej and Indus rivers. The people in the Indus valley during the third millennium B.C. used wool for their warmer textiles and cotton for their lighter ones. No textile of this age could be preserved because of the saline nature of the soil of the valley, only the statues found in sight give sufficient proof that hand spun and hand woven shawls were in fashion then. The Moghul kings gave great impetus to the wool industry in Kashmir. The emperors of the Moghul period were patrons of fine art and culture. During Akbar s time specially Kashmir shawls were sent as valuable gift for kings every time. By the end of the 18th century the Kashmir shawls had a vast market in Persia, Afghanistan, Russia and Europe. So popular was the shawl in Europe that England thought to shift the shawl industry to Paisley. This however gave a serious blow to the industry and by the end of the 19th century Kashmiri shawls became a thing of the past. Fortunately, today the shawl industry is again reviving. The popular woollen goods are the Pashmina shawls, both woven and embroidered, the Shahtus, Gabha, Namda, Lohi, etc. Thousands of Namdas are exported to the United States and earn valuable foreign exchange. At present, the wool manufacturing countries are Australia, New Zealand, The British Isles, South America and South Africa. Not only wool but also hair from the camel, goat and rabbit is used for making woollen fabrics. Varieties of wool and their origin All wools are classified as fine, medium, long and carpet wool. 52

61 Wool - The Protein Fibre Fine wool: The merino sheep is the outstanding example which supplies this type of wool. Fine wool may vary in length from 1½ to 5 inches. We get this wool from merino sheep. The original merino sheep were from Bikaner, India, these were taken to Australia. They are noted for softness, fineness, strength, elasticity and superior spinning and felting qualities. They are used for high quality flannel, knit goods, broad cloth, meltons and other face finished fabrics. Medium wool: These are by Oxford, Hampshire, Suffolk and Dorset. Long wool: Large sheep such as the Lincolns Cotswold from Leicester produce long strong, lustrous wool. The fibre length varies from 5 to 6 inches for a Romney marsh, 10 to 15 inches for a Cotswold. This is coarse wool with poor felting quality, they are used for coarser tweeds, serge, overcoating, blankets, braids and worsteds. Carpet wool: This wool is procured from various crossbreeds. As the name implies it is largely used in the manufacture of carpets and rugs and for other coarse fabrics, horse blankets, coarse upholstery fabrics, etc. Structure of wool Figure

62 Natural and Man-Made Fibres Wool is a natural protein fibre. It is composed of a chain of amino acids combined by condensation (eliminating water) through peptide linkage to form chains. Wool is composed of five elements in approximately these percentages: carbon 50%, oxygen 22-25%, nitrogen 16-17%, hydrogen 7% and sulphur 3-4%. In addition, there is a very small amount of mineral matter present in the fibre. The weakest part of wool are the sulphur linkages, they are the parts most readily attacked by oxidizing and reducing agents, and even by light. Most clean wool is off-white in colour, although grey, brown and black wooled sheep are not uncommon in the various breeds. Wyoming wool is the whitest produced in the United States. Colour is due to the pigment in the cortical and medullary areas of the wool; the scales are not pigmented. Lustre is due to the nature and transparency of the scale structure of wool; it varies among animals and breeds, with the area of a fleece and with climatic conditions. Wool is made of three distinct parts. The outer horny transparent flattened scales. A cylindrical cortical layer (cortex which makes up the soft plastic bulk or body). 54 A medulla or central air filled canal. These are made visible under a microscope. The scales vary in size and shape and the free ends projecting outward and upward towards the tip of the fibre. In the finest wool, the scales encircle the fibre and fit one into another like stacked cups and bowls. In coarser wool, the scales overlap like shingles on a roof, and there may be several encircling rows depending on the diameter of the fibre. The scale structure make wool identifiable.

63 Wool - The Protein Fibre The scale structure forms a protective hide for the more delicate part of the fibre and gives it form and a certain degree of rigidity. The cortical layer is responsible for the strength and elasticity of the fibre. The medulla increases the insulative property of the fibre by incorporating a built-in air space. Wool like human hair is an outgrowth of the skin. It grows from the hair follicle which also has sebaceous glands attached and which serve the same function as those adjunct to human hair. Molecular structure of wool The protein fibre have complicated molecules composed of varying numbers and kinds of amino acids, which have combined to form long chains. 20 amino acids have been identified in wool. Larger amounts are glycine, alanine, serine and tyrosine. These are largely the group that form proteins called keratin. Wool contains a large amount of glutamic acid (16%) has considerable amount of cystine, leucine, serine, arginine, aspartic acid, proline, threonine, glycine, tyrosine, valine and alanine. The general chemical formula for amino acids is: Figure 5.3 The folded chain structure of wool is believed to straighten out when pull or pressure is exerted on the wool fibre, and to revert to its original position when released. The unfolding refolding ability of the chain would account in large measure for the high degree of elasticity, elongation, resiliency, and crease resistance of wool fabrics. The side chains between molecules are believed to hook together to give still more resistance to packing or crushing. The cystine side chains, composed in part of sulphur are believed to form stable links at the sulphur atoms between different chains. 55

64 Natural and Man-Made Fibres Other linkages occur between molecular chains also but they are less stable than the sulphur bonds. The following diagram is a possible linkage between molecular chains, showing both sulphur and salt linkage as theorized by Astbury and Speakman (Figure 5.4). 56 Figure 5.4

65 Wool - The Protein Fibre Figure 5.5. The ziz-zag molecular structure of wool. Properties Wool is said to be a poor conducter of heat. However, the amount of heat conducted along the fibre is not the important factor in the warmth of wool. Wool fibres do not pack well because of the natural crimp. This makes the wool fabric porous and capable of incorpoting much air giving the fabric a lofty hand. Absorbency: Absorbency is defined as the ability of a fibre to take up moisture and is expressed in terms of moisture regain, which is the percentage of moisture that a bone dry fibre will absorb from the air under standard conditions of temperature and moisture. Absorbent fibres make fabrics which are comfortable on hot humid days or in damp climate. Absorbent fibres do not build up static electricity, which also makes them more comfortable in dry cold weather. Absorbent fibres are hydrophillic or water loving while non-absorbent fibres are hydrophobic or water repellent. Absorbency is important from the beauty stand point since it makes easy dyeability possible. Absorbency is also related to resiliency. Fabrics made from the hydrophilic fibres tend to crush more when damp. Absorbency is due to the chemical composition and the molecular structure of the fibre. Cellulose fibres which have more hydroxyl groups (OH), protein fibres which have reactive amino (NH2) and carboxylic groups are very absorbent. Fibres which have few reactive groups are not absorbent. Highly oriented groups are less absorbent than fibres with many amorphous areas, since there is no space for water 57

66 Natural and Man-Made Fibres molecules to enter. Wool does not take up water quickly. Wool can absorb 30% of its weight without feeling wet. Resiliency: This is greater when it is dry. This property is important in the manufacture of fabric because it permits energetic mechanical treatments in finishing woollens and worsteds. Press retention is good. It holds crease well. Crease is set by moisture, heat and pressure. Wool fibres are weak but fabrics are durable. Felting: It is a term applied to progressive shrinkage of wool. Felting occurs when wool is subjected to heat, moisture and friction (conditions present at the underarms of sweater and shirt and soles of socks). To make felting possible a fibre must have a surface scale structure. Felting is also a disadvantage as it makes washing of wool difficult. Amphoteric nature: This means it will unite and react with both acid and basic dyes. Wool is very stable to acids but it is harmed by alkalies. In the manufacture of fabrics acids are used to remove cellulosic impurities. This process is called carbonizing. Elongation: Elongation of wool is 20 to 50% and both elongation and elasticity are higher when the wool is wet. Processing Shearing: It is the process of clipping the fleece from a living animal. Sheep are sheared once or twice a year, depending on their locality by travelling crews. An expert shearer can clip 100 to 200 sheeps a day. In most parts of the world shearing is done only once a year in late spring or early summer. Shearing is a high paying job in range areas. Skill is reqired to sheer the sheep and leave as much wool on its body to protect the animal from the sun and the rain. 58

67 Wool - The Protein Fibre Pulling: Pulled wool is obtained from animals which are sold for meat. The pelts are washed and brushed and then treated chemically to loosen the fibre. The yield of pulled wool is one fifth of sheared wool. Wool as it comes from the sheep is called grease wool, as it contains impurities such as sand dirt, grease and dried sweat. The grease in stages of purification is used for a wide variety of other commercial products, such as medicines softeners, toilet preparations. Sorting: Wool is sorted according to quality and dirt is removed by machine known as duster. The best quality of wool comes from the shoulder of the sheep and the sides of the sheep and the poorest quality from the lower legs. Physical structure Fibres of wool vary in length from 1 inch to 14 inches and in thickness from 10 to 70 microns. 18 to 30 micron fibres are used for clothing, coarser wool is used to make rugs. High quality wool does not imply high durability. Identification Figure 5.6 The alkali test A hot 5% solution of alkali will destroy wool completely, as it disintegrates the fibre and it becomes slick, turns to a jelly like mass, and goes into solution. Alkali is sold in the market as lye. The wool with a blend will dissolve leaving behind only the fibre that has been blended. 59

68 Natural and Man-Made Fibres Recipe for lye 1 tablespoon lye. 1 pint water. Heat to boil. Burning test Pure wool burns with the odour of burning hair. Care Garments should be allowed rest between wearings so that they shrink back into shape. Hanging over hot water removes wrinkles. Garments should be hung so that the air can circulate freely because they tend to hold odours. Wool does not soil readily. They should be brushed after each wear. Wool should never be rubbed too hard during washing. Wool garments should be placed on a flat dry surface for drying for good shape retention. Wool cannot take the rough treatment given to cotton. While washing it has to be delicately washed. By-products of wool Wool has a very valuable by-product, largely recovered from the yolk. Yolk is made up of wool grease and perspiration. The grease of wool is an unusual kind of wax, in purified form it is called Lanolin. Lanolin has a peculiar quality in its ability to penetrate human skin, carrying with it pharmaceutical or other desired products. It is also used in leather goods trade. Speciality wool The Cashmere goat This animal lives in the Tibetan region of the Himalayas. It receives its name from the province of Kashmir. The hair of this goat has a distinct silky gloss and is smoother and warmer than 60

69 Wool - The Protein Fibre Figure 5.7 wool. Kashmir woollen goods are of two varieties. The fleece of the domestic goat is called the Pashm and that of the wild goat is called Asli or Shahtus. The hair is combed by hand for the animal in the moulting season. Only a small part of the fleece is very fine probably not more than ½ a pound [per goat]. Mohair The importance of mohair a product of the angora goat is shown by the fact that pounds of this fibre is clipped in Texas, Oregon, Missouri, Arizona and California in the United States. The mohair fibre is white in colour. It is long lustrous, fine and strong and possess excellent spinning qualities. Figure 5.8 Mohair lacks the felting quality of wool. This limits its use in apparel only. The Llama The Llama is an aristocratic member of the camel family. It is valuable as a fur bearing animal and is also known as the beast of burden. Although Llamas will refuse to carry more than a limited number of pounds, they are used in many instances because it costs nothing to feed them and their quality of hair is a valuable textile fibre. The Llamas occur in the pacific coastal region of 61

70 Natural and Man-Made Fibres South America. The Llamas and the Alpacas are the domesticated species. The Guanaco and the Vicuna are the wild species. The natural habitat of Llama is the southern Ecuador, Peru, Bolivia and northern Argentina. The entire body of the Llama is covered with a thick coat of long hair, but the hair close to the body is fine hair. The Alpaca Alpaca is another member of the camel family which furnishes a Figure 5.9 fibre of commercial value. Both Llama and Alpaca fibres are similar to mohair in character. Alpaca fibres constitute a large portion of wool fibre, other than the sheep, appearing on the market. This wool is white, grey, fawn, brown or black in colour. Other Important Hair Fibres Fur fibre is now used as novelty fabric. The most important of these Figure 5.10 are the angora rabbit and the common rabbit. Fur fibres of the muskrat, beaver, raccoon and squirrel are used as fabric. Hair fibre although of minor importance are those of the hog, cow, horse, and even human hair. These are occasionally used for construction of novelty fibre. 62

71 Chapter 6: Silk - The Queen of Textile Fibres T he manufacturing of silk dates back to 2640 B.C. Silk has been considered one of the most elegant and luxurious of fibres. It is still recognised as such all over the world. It is called the queen of all textile fibres. There are several species of silk producing caterpillars, but the mulberry silkworm, or bombyx morri produces most of the commercial silk fibre. These mulberry silkworms have been cultivated for many centuries. There are other associated varieties which live on the scrub oak and produce the fibre known as wild silk. Antiquity Figure 6.1 Silk was discovered by a Chinese empress in 2640 B.C. The Chinese carefully guarded the secret of the silk cocoon for 3000 years. They wove beautiful fabrics which were sold to Eastern

72 Natural and Man-Made Fibres traders at a high price. In 300 A.D., refugees from china took cocoons to Korea and started raising silk- worms. Japan learnt about silk from Korea. The industry spread through central Asia into Europe, and by the 25th century Italy was the silk center of Europe. This was later taken over by France in the 17th Century. Weaving of silk became important in England when the huge number of weavers emigrated from France to England in Sporadic attempts were made by the United States to cultivate silk. But the climatic condition of the north was not able to grow mulberry trees and in the south cotton was being cultivated because of the country s need. Since the introduction of nylon for hosiery, half of Japan s market for silk was lost. Silk can be produced in any temperate climate, but it has only been successfully produced where there is cheap and abundant labour available. In India, Kashmir and Karnataka produce a lot of mulberry silk. Other varieties of silk Eri, Muga are produced in the northeast of India. Tasar silk is produced in Uttarakhand. India produces more than 7% of the worlds silk output. Production of mulberry silk in India has been on the rise and growth has been gaining momentum on account of abundant natural resources and cheap labour. Still techniques of cocoon production is considered to be of low level by international standards. Though 70% of the world mulberry silk is produced by China and Japan, India can boast of producing all kinds of silk viz. muga, mulberry eri and tasar. Presently eri silk is being produced primarily in Assam. Eri silkworms are hardier than mulberry silkworms and can be reared with greater ease. The rearing of these worms requires very little investment. The fabric formed from the eri worm is as soft as cotton and as warm as wool. Eri silk is preferred for winter clothing. The yarn has poor affinity to dyes and the bleached yarn 64

73 Silk - The Queen of Textile Fibres shows yellowing over years. Eri fabric lacks crease resistance and shows sagging properties and therefore it is not preferred as normal dress material. Eri culture has a high potential as a subsidiary occupation to augment farmers income in north-eastern India. Eri silk can be processed into the most comfortable warm clothing. Eri is also spun in combination with muga or tasar silk waste or cut cocoon to give a rigid texture and an attractive look for use in suiting or upholstery. Figure 6.2 In respect of mulberry silk in India, Karnataka s share is about 63% while that of West Bengal is about 12%. The remaining 12% is produced elsewhere in the country. In Karnataka, the principal districts for the production of silk are Kolar, Bangalore, Mandya, Tumkur and Mysore. Andhra Pradesh is fast improving its silk production. Sericulture is introduced in large scale in Vishakhapatnam, Mahbubnagar and Anantapur districts of the state. In Tamilnadu, sericulture was originally confined to 65

74 Natural and Man-Made Fibres Dharampuri and Coimbatore districts but later extended to Ramnadhpuram and other districts also. In Uttarakhand, majority of cocoons are produced in Doon Valley. In Manipur, cocoon was reared by one community called Loi. However, the productivity of mulberry silk in India is the lowest as compared to China and Japan. In order to enhance the productivity, Karnataka has launched a very ambitious project of Rs. 80 crore under the sponsorship of world bank known as Operation Silk. Apart from increasing the production, silk exchange centers were set up with a view to put a stop to the exploitation role of middlemen and traders. A price stabilization and development fund would ensure a fair return to the farmer and also hold the price line. Sericulture is an agro based industry with considerable employment potential. A very significant characteristic of this industry is its ability to provide gainful employment to sizable sections of rural masses without dislodging them from their home stead. It assures cent percent employment to women. The industry qualifies very well as cottage based rural industry, which can be practiced using community ownership and common working place utilizing local labour and resources. Employment potential can be created in the rural areas by increasing the sericulture activities right from mulberry cultivation up to production of the fabric. The industry also gives inputs to other industries like nutrients to agriculture, raw material for soap, fruit processing industry, timber, besides production of various important products like surgical gloves. The silk industry gives social respect to women ensuring healthy environment and sustainable development. 65% of the silk produced is utilized by the Indian women due to their interest in fashion and silk. It is an industry by the women and for the women. 66

75 Silk - The Queen of Textile Fibres Among the large varieties of silk goods produced in India for the domestic and export markets are: Mixed/blended silk fabrics. Dress material. Sarees. Scarves and stoles. Made-up articles like cushion covers and bed spreads. Silk carpets. Silk garments. The world market for silk and silk products is a lucrative and growing one. Developing countries that already produce silk in various forms or that have the potential to do so should explore the requirements for products and develop market in this sector as one of the means to increase their export earnings. More than 90% of the world market for silk garments is accounted for by women s clothing. This covers a wide range of items from lingerie to high fashion evening wear. Silk goods for men include shirts, ties, socks, underwear and to a limited extent, knitted goods. The main importer of silk is U.S.A. to the tune of 25% of the total Indian silk exports, followed by Germany, U.K., Switzerland, U.A.E., Italy, Singapore, Japan, Canada, Austria, The Netherlands, Belgium, Poland, Australia, etc. The main items of export are dress material, made-up articles (pillow covers, cushion covers, scarves, curtains, bedcovers and silk paintings), ready-made garments, sarees and ties. The items are mainly exported from New Delhi, Kolkata, Mumbai, Chennai and Bengaluru. 67

76 Natural and Man-Made Fibres Silk Industry The silk manufacturing industry is divided into four parts sericulture, reeling, throwing and manufacturing. Sericulture Sericulture is the name given to production of cultivated silk. The sericulture process begins with the silk moth which lays eggs on especially prepared paper. The eggs are kept in cold storage until they are needed for hatching. Hatching takes place continuously throughout the mulberry growing season. Thus, making it possible to keep labour and equipment at a minimum. The eggs are hatched into caterpillars, which are put on special mats and fed fresh mulberry leaves. The newly hatched worm is about three millimetres long, almost black in colour and weighs about.005 gram. Only the tenderest young leaves can be fed to the young worms. If the leaves are wet, they must be wiped dry. Fresh leaves must be supplied every hour and tray kept clean. The temperature and the humidity of the room where the worms are kept must be controlled. During its growth the worm passes through four sleep and wake cycles. During those four sleep periods it ceases to eat. These are followed by moulting when it sheds its out grown skin. During wake period, it is a voracious eater and grows rapidly. The fully developed worm is milky white in colour. It increases in weight approximately 10,000 times. It ceases to eat and lifts its head to in search of some thing on which to spin its cocoon. The worm first spins a net and then forms a case or shell called the cocoon. To do this it doubles itself on its back, with its feet on the outside and with many movements of its head spins the cocoon by secreting a viscous fluid produced by the two glands in its body. The silkworm makes more than one movement of its head in one minute, some 300,000 turns are required to spin the cocoon. The worm can no longer be seen but it can still be 68

77 Silk - The Queen of Textile Fibres heard working away until the cocoon is spun in two to three days. The fibre is spun back and forth in the form of figure eight. The caterpillar changes into cryssalis. This is the third stage of life, if the crysallis is not destroyed, a moth develops in about two weeks. This moth secretes an alkaline solution which so weakens the fibre that they are easily broken and it can push its way out to the bottom of the cocoon, though this place has less strands but many are broken in this process. The mother moth spends the few days of its life just laying eggs. One ounce of eggs will produce from 100 to 150 cocoons. The discovery of an effective method of killing the crysallis without injuring the silkworm was an important step in the production of silk. Sericulture is carried on by highly specialized methods for two distinct purposes, first the production of disease free eggs for breeding, and second the production of raw silk for use in the industry. Raising of worms for the production of silk requires well equipped establishment. Figure

78 Natural and Man-Made Fibres When the silkworm is grown, it spins a fibre cocoon around itself. The bulk of the silk moths are killed inside the cocoon by boiling and only those which are needed for reproduction are allowed to emerge. The pierced cocoons are used for staple fibres. The silk fibre is a double strand of thread held together by a gum serecin, a water soluble substance secreted by silkworm. The serecin is a very important part of the silk fibre. It serves as a warp sizing for the silk yarn as they are threaded on the loom and woven in to grey goods. Because of the serecin the silk yarn can be used without twist. When the serecin is removed from the fibre in the degumming process, the fabric structure becomes more mobile. The low twist and the mobile structure are major factors in the dry tactile hand and the liveliness, suppleness and drape of silk fabric. Zero twist yarns are important in the good covering power of silk. Triangular cross-sections, longitudinal striations and fine denier are other important factors that contribute to the aesthetics of silk. Reeling Reeling or unwinding silk from the cocoon is done in an establishment called the filature. Automatic reeling is done by lacing the cocoon threads through a guide to a chemical bath which softens the thread. The filament go around a revolving horizontal roller, which dries and winds them onto a spool or cone ready for weaving on delivery. The automatic reeler also has a cocoon finding mechanism which regulates the size and uniformity of yarn. The machine increases production many times and cuts labour. In India, bulk of the reeling is done adopting charka and cottage basin. In the case of charka reeling large number of people are employed. In large basin reeling yarn quality is improved to a large extent. During the process of reeling large quantities of silk waste are obtained. This is composed of inner and outer layers of cocoon which are removed during reeling. In local hybrids 20 to 70

79 Silk - The Queen of Textile Fibres 30% silk comes as waste. The silk waste is divided into three parts: 1. Blaze and unreelable cocoons. 2. Reelable waste. 3. Throwesters waste. Before spinning a cocoon, the larva builds a hammock an anchorage to hold its cocoon. These are the first threads secreted by the silkworm, when it mounts a cocoonage to form its cocoon. The quality is poor and the quantity is small, but it can be used for noil spinning. Some wastage occurs while finding the end of cocoon filament before reeling. This is known as Knubbs or Kibizzo, although the term basically refers to reeling waste in respect of univoltine quality. Throwing Throwing is the process of combining several reeled strands to make a yarn. The number of strands are combined and the amount of twist they are given is determined by the use to be made out of the yarn. Thrown or reeled silk yarns are classified as singles, tram and organzine. Singles: Singles are strands of raw silk consisting of three to ten double filaments to which twist may not have been added. Tram silk: It consists of two or more strands of singles slightly twisted together. These are generally used for filling and are often made from imperfect fibres. Organzine: It is formed by twisting yarns in opposite directions. As this is used for warps it needs to be strong and is therefore made from the best strongest fibres. Silk and sericulture remained as a sector for women in almost all third world countries. It is also noticed that till this tradition continued, position of women in their respective family was higher 71

80 Natural and Man-Made Fibres and atrocities on women was almost unknown. But with introduction of modern technology like filature, spinning mills and modern textile mills. Role of women in economic activities was reduced, they consequently lost their status and atrocities increased. It also caused widening of gap between absolute poor and absolute rich. If we have to consider benefit of our society, we shall have to consider the social cost of women development. Chemical structure of silk Approximately 66% of raw silk is the fibre of fibrion, 22% sericin, 11% water and 1% oil and colouring matter. In order to free the fibrion from its glue like case of serecin and render it capable of acquiring dyestuff and a satisfactory finish that will enhance the beauty and sheen of the silk, it is Figure 6.4 necessary to find a solvent for sericin. Silk like wool is a protein fibre. Therefore, it yields amino acid upon hydrolysis CO-NH groups. It is quite similar to wool in general behaviour. Heat: Silk can be heated to a higher temperature than wool without disintegration. However, if white silk is held at 231 F for fifteen minutes it becomes pale yellow. For this reason, silk garments must be dried carefully after laundering and should be pressed quickly with an iron that is not too hot. Silk disintegrates above 330 F. Silk is attacked by the ultraviolet rays of the sun and acid forming gases and moisture. Weighted silk is more quickly injured 72

81 Silk - The Queen of Textile Fibres than pure silk. After six hours of exposure to an ultraviolet lamp silk loses 50% of its strength. Water does not permanently affect silk fibre. It decreases about 20% strength when wet. It regains its original strength after drying. The fibre swells, but does not dissolve when steeped in warm water. Acids: Silk is more readily affected by the action of strong acids such as sulphuric, nitric, and hydrochloric than wool, dissolving readily in these reagents. Dilute solution of nitric acid produces a bright yellow colour on silk similar to that formed with wool. Silk is affected by hydrochloric acid in any form. This fact permits the use of this acid in separating wool from silk in analysis. If silk is treated with concentrated sulfuric acid only for a few minutes and then rinsed and neutralized, it shrinks and has less lustre but shows little loss in strength. Dilute acids are readily absorbed by silk. They increase the lustre and develop a scroop. Tannic acid is used as a mordant and in weighting. Bleaches: When entirely degummed the silk fibres need little bleaching. If the fibre is not white or incase some of the gum is retained bleaching is done with the same reagents which are used for wool namely sodium peroxide. Javelle water makes silk yellow and tender. Javelle water contains sodium hypochlorite which tends to decompose and liberate chlorine. Chlorine is a good oxidizing agent. It attacks stains and colours and in case of silk attacks the fibre also. Dyestuff: Dyestuff are absorbed by silk more readily and at a lower temperature than any other natural fibre. Since it is a protein fibre it possesses both acid and basic properties and therefore reacts with both basic and acid dyes. 73

82 Natural and Man-Made Fibres Perspiration: Silk garments often break under the armpit or across the shoulder before the remainder of the garment is worn out owing to the effect of perspiration. Deodorants which contain aluminium chloride also cause a tendering of the fabric. Perspiration becomes alkaline and tenders the silk. Weighting: Silk fabrics, if woven in the gum are somewhat stiff, and yellow. When the gum (serecin) is removed prior to the finishing and dyeing process, 20-25% of the weight of silk is lost. Silk manufacturers sometimes use metallic salts in processing silk. Stannic chloride is used for weighting unless the material to be used is to be dyed black. In that case, iron salt and logwood are used. Physical characteristics of silk It is the most expensive textile fibre. It is stronger than any other natural fibre. It retains 80% of its strength when wet. It has the advantage of being the lightest in weight. Silk is the longest, lightest in weight, strongest for equal cross-section and finest of all natural fibres. Silk absorbs moisture from the atmosphere. Silk is a poor conductor of electricity. Scroop, that peculiar crackling sound which is emitted when silk is rubbed together or squeezed in the hand, may be said to be acquired rather than natural. One of the properties of silk that makes it a practical fabric for garments is the ease with which it can be cleaned. The smooth surface and freedom from short fibres causes it to shed dust and give a good appearance. 74

83 Silk - The Queen of Textile Fibres Characteristics of Silk Fibre Microscopic appearance Length Diameter Colour Lustre Strength Longitudinal-double transparent filament yards 9 to 11 microns Light to dark cream High grams per denier Elasticity High (15-20%) Heat conductivity Scorches easily Water absorbency 30% Standard regain 11% Effect of moisture Effect of sunlight Attack by mildew Attack by moth Attack by carpet beetle Effect of acids Effect of alkali Cross-section Reduces strength by 20% and increases elasticity Very sensitive Yes No Yes Less resistant than wool More resistant than wool Triangular SWOT Analysis of Silk Industry in India Strengths The silk industry enjoys a growing domestic market since silk is a part of a culture and recognised as a symbol of purity one product viz., saree consumes over 85% of silk produced and saree as a garment is one of the most elegant dresses in the world. 75

84 Natural and Man-Made Fibres Silk being a natural fibre enjoys increased patronage in the highly ecology and environment conscious world. Silk is exclusive and considered a luxury item along with gems and jewellery. It would therefore enjoy the support from the upper strata and growing middle class. Silk is an important bridal wear. There appears to be no dearth for traditional saree designs for creating exclusive items. Hand-woven silks are extremely popular in the west export markets which are wide open with no threats of quota like other fibres. Silk is only 0.2% of the total textile fibres produced and this percent share is expected to decrease with steep increase in production of other fibres. This situation would maintain an increase in demand for natural silk. With lightweight silk becoming popular for dress material and printed sarees the market for silk is getting broad based within the country. India holds a monopoly in the production of yarn dyed silk. Weakness The industry in all sectors of production is highly decentralized. It is also seen as a cottage industry activity. The decentralized nature of the industry has failed to attract the attention of business and commercial banks, resulting in poor financial support to the activity. The producers such as rearers, reelers, weavers, dyers and printers do not have the capacity to invest to adopt new 76

85 Silk - The Queen of Textile Fibres technology. The obsolete and outdated equipment used cannot do quality production, and is not cost effective. No availability of skilled labour. Opportunities Silk as a natural fibre is more acceptable to both domestic and export markets. The domestic consumption of silk is estimated to cross 25,000 MT in the next few years. If quality aspects are kept in view, sky is the limit for India silk. Garment export is steadily increasing. Tremendous opportunity exists in the export of garments besides quantity increase. Garment manufacturing has provided maximum opportunities for gainful employment to women Threats The inability of the silk industry to react to the changing needs in terms of quality in the domestic and export market is a major concern. The basic producers being financially weak may not be in a position to face the stiff challenges of the market in the coming years. The market demand for better and better quality products of lower prices is bound to exert a lot of pressure on the production activity. Heavy dependence on imported silk yarn for export is risky. Any change in Chinese policy could jeopardise Indian export. Exporting unit are not very innovative in design and colour combination. This could be a drawback in the ever-changing trends and taste in the export market. 77

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87 Chapter 7: The Non-Thermoplastic Man-Made Fibres - Rayon A ll the man-made fibres have some process in common. They have been produced from non-fibrous material, in the process loose their fibrous nature to being in viscous state to be reformed into fibre. This is done to by forcing the solution through the device called spinnerets. All the fibre then coagulates or hardens within a reasonable time after leaving the spinnerets so that they will not stick together and may be wound on bobbin or cones, or be deposited in pots as cakes of yarn to be readied for conventional processing into fabrics. The non-thermoplastic group of man-made fibres include several subgroups: those of cellulosic origin, alginates, minerals, and protein based fibres. The largest group at present are the fibres of cellulosic origin all of which are identified as rayon in the Federal Trade Commission (FTC). The non-thermoplastic fibres, except for the mineral fibres may be cared for much as cotton, linen, silk or wool whichever they most resemble, both in visible characteristics and in their reaction. They are not softened by heat so will not melt if ironed although they will scorch if ironed at sufficiently high temperature. As a group they are soft absorbent, pliable, comfortable to wear, do not pill, do not accumulate static charge and are not subject to attack by moths. In longitudinal view under the microscope, in common with most other man-made fibres they look alike. All appear as smooth rods, black specked if delustred but with no characteristic by which the individual fibres can be positively identified.

88 Natural and Man-Made Fibres The Rayons (Cellulosic Fibre) Rayon is a manufactured fibre composed of regenerated cellulose in which substituents have replaced not more than 15% of the hydrogen of the hydroxyl group. By this definition rayon includes viscose rayon, cuprammonium rayon, Fiber E fortisan, Topel, corvel Fiber Fm 27, Avril (Fiber 40, Zantrel). It is an interesting fact that much of the rayons early development is tied to the attempt to develop filament for incandescent electric lamps, then newly discovered by Thomas Alva Edison. Many developments of rayon explore in considerable detail the early suggestions and attempts for making artificial silk without the benefit of silk worm. Dr. Robert Hooke and Rene F. Reaumur who predicted such a possibility in 1664 and 1710, respectively. F. G. Keller (1840) inventor of a mechanical process for producing wood pulp, and Louis Schwabe (1840) who experimented with a crude type of spinneret for drawing thread for drawing various solutions through holes in thread form. Nitrocellulose was the first to be produced successfully and commercially. The early history of this kind is of importance. In 1855, Georges Aeudamers (Switzerland) patented a process of transforming nitrocellulose solution into fine threads. The rayon and staple fibre handbook has given this account of Chardonnet s work: From a textile point of view, Count Hilare de Chardonnet began his work in 1878 and obtained his first French patent on November 11th, 1884, cumulating all the efforts of his predecessors Hooke, Reaumur, Audamers Ozanam, Weston, Huges, Powell, Evans, Wynne, Crooks and Swinburne. His labour won him by general acclaim the title of father of rayon industry. 80

89 The Non-Thermoplastic Man-Made Fibres - Rayon He was a purposeful research worker, a pupil of Pasteur and trained at the Ecole Polytecnic of Paris. Chardonnet made a careful study of the silk worm and its method of producing silk. He based his procedure on this study to exhibit the fruit of his labour in The great Paris Exhibition attracted the attention of capitalists, who provided the funds for the first artificial silk factory at Bensancon, his birthplace, using the nitrocellulose process. Within two years many technical problems were overcome in connection with large scale production, denitration and rendering the filament non-inflammable. This marked the birth of the commercial rayon factory. The process was crude and many improvements and modifications had to be made. But Chardonnet lived to see the fruit of his labour. He saw the commercialization of rayon before he died in Improvements have been made ever since the first rayon was produced by Chardonnet. Today we have rayons which have little resemblance to their originals. We now have rayons varying in lustre from dull to very bright, in a wide range of deniers from very fine to coarse. To date rayon is consumed in large amounts for fabric usage and is very cheap compared to cotton. How is rayon used? Rayon and acetate both found usage in home furnishing 27%, juniors wear 17% and boys wear 9% and girls wear 2%. Most of the rayon and acetate was used for tires, cords, transportation upholstery, tents, carpets rugs, curtains, bedspreads, coats, knitted wear, woven underwear, suits, blouses, skirts and other items. A large amount went into nightwear and underwear. The rayon fibre has a number of properties in common with each other and with cotton and linen. They burn readily with a yellow flame and with the odour of burning paper or cotton leaving a little cobwebby residue which crumbles into fine, powdery grey ash. The rayon 81

90 Natural and Man-Made Fibres may be successfully fire retardant treated, they are all sensitive to acids but are not generally damaged by alkali. Most of them have low resiliency and elasticity and without special crease resistant treatments wrinkle considerably and need to be ironed frequently. Crease resistant treatments are very commonly applied to many of the fabrics made from these fibres. Manufacturing process of rayon Preparation of cotton linter cellulose: linter are small fibres adhering cotton seeds. They are removed after ginning. They are removed at the mill where the seed has to be used for oil and other products. All linters are removed from the process called mill run or in two ginning processes. If the two are used the first ginning cuts are used by the mattress industry or for cheap qualities of cotton fabric. The second and the shorter cut is less expensive and is cleaner. It becomes the cotton for chemical cotton, much of which is utilized in the man-made industry. The initial quality of the linters depends on their quality of the linters and the condition in which the seed has been received at the mill. Different lots of linters are blended to achieve a uniform quality of chemical cotton. The cleaned blended linters are carried to the digester where the fibres are mixed with dilute caustic soda solution (NaOH) then are carried into the digesters for cooking process. Temperature, pressure, time, and proportion depend on the product desired, all processes are carried out under carefully controlled conditions. At the right time the linters are removed from the digester and washed in soft water to stop the action of the alkaline solution. The cooked linters are then bleached with chlorine, rewashed thoroughly and dried. The method of utilizing these linters for the manufacture of linen differs for each process and the difference in method results in characteristic differences in the quality of fibres and hence fabric. 82

91 The Non-Thermoplastic Man-Made Fibres - Rayon Spinnerets are also called spinning jets, must be made with extreme care and polished until no possibility of the slightest roughness remains anywhere. The instruments of making holes in the spinnerets are finer than the human hair and the holes should be uniform in size and exceedingly smooth. Spinnerets are made from platinum and platinum alloy for viscose rayon and other processes where fibres coagulate in chemical baths but may be made of steel or other metals for air or water coagulating processes. Viscose rayon Figure 7.1 Viscose rayon is largely cellulose which is prepared by processing wood or cotton, but in dissolving the original cotton or wood and regenerating the cellulose in a new fibre the degree of 83

92 Natural and Man-Made Fibres polymerisation has been reduced. This accounts for many differences in properties, especially the greater sensitivity of rayon than cotton to physical and chemical change. Viscose rayon can be made from purified cellulose, which is prepared from processing wood or cotton linters or a mixture of the two. When received at the rayon plants the cellulose sheets are unpacked and stored in rooms where the temperature and relative humidity are under control. A pound of viscose fibre requires approximately these amounts of various raw material 1.15 lbs of wood cellulose, 1.0 lbs of sodium hydroxide, 0.4 lbs of carbon disulfide, 1.5 lb of sulphuric acid, 1.0 lb of sodium sulphate, 0.2 to 0.5 lbs of glucose or corn sugar and 800 to 1700 lbs of soft chemically pure water. Sodium sulphate adds strength and is said to be responsible for the serrated cross-sectional shape. The glucose or corn sugar gives pliability and softness to the yarn. The coagulated fibres are lead through a guide to a bobbin or to a spinning pot that rotates rapidly inserting a little twist into the filament by centrifugal force, throwing the resulting yarn to the outside edges of the pot so that the cake of the yarn is built from the outside edges of the pot so that the cake of the yarn is built from the out side in toward a hollow center (Figure 7.1). The diameter of the fibre is dependent on the amount of stretch imparted. The size of the holes also do have an influence on the diameter of the fibre. The stretch orients the fibre into making the molecular chains more parallel, thus increasing crystallinity and giving added strength and rigidity. At the same time reducing pliability. Coagulating the fibres in a liquid bath is known as wet spinning. After being coagulated in the acid bath as filaments and collected in pots, on bobbins the fibres or yarns are washed to remove all traces of chemicals. Sometimes they are bleached 84

93 The Non-Thermoplastic Man-Made Fibres - Rayon although most rayon come through processing in a nice white colour. Fibres in all forms are than dried on a trip through a tunnel dryer. Fibres and yarns are then ready for handling on regular equipment in the same way as other fibres of comparable length. Oil is often added to the fibres as a lubricant before packaging to soften and protect them in weaving and spinning. Instead of individual steps for this process a continuous method has been developed and is in use in several plants. By this method the filaments as they come in coagulating baths are run over a series of moving reels with very accurate controls, where continuous sprays of the various finishing solutions fall upon each filament along a fixed part of the route; by the time the last reel is reached the filament has had all the treatments, are dry and ready for twisting and winding in skeins or on cones. The reels are adjustable so that any degree of stretch may be applied to the fibre, which is still not set from their coagulating bath. Properties Under the microscope in longitudinal view, viscose rayon fibres appear much as smooth glass rods although under high magnification striations may be visible parallel to the fibre length. In cross-section the fibres may be round, oval or flat but all show serrated edges. The typical serrated edge is a positive means of identifying the fibre. Elongation varies from 9 to 30%. Rayon exhibits a property called creep or delayed elasticity. It takes days to get back in its shape after it has been stretched. Elasticity and resiliency both are low, so that rayon wrinkles badly unless treated with special finishes. Resin treatments on rayon are more successful than any other man-made fibre and is usually quiet permanent. The specific gravity of rayon is 1.52 about the same as cotton which is medium 85

94 Natural and Man-Made Fibres among fibres. It is very absorbent and exhibits about 11 percent hygroscopicity. It dyes in darker colours than cotton does. Dyes must be chosen carefully for mixtures and blends, or the rayon will have exhausted the dye even before the other fibre has had a chance of even getting wet. Rayon does not accumulate static electricity. Resin finishes may alter some of these properties. Viscose looses some strength on prolonged exposure to sun light. It is more resistant to light than silk but less than acetate orlan, and fortisan. Rayon can be satisfactorily laundered like cotton and can be ironed at the same temperature as cotton. Boiling and sterilising the fabric is not advisable. Clean dry viscose is not attacked by moth and mildew. Cuprammonium process The first step is to moisten the cellulose with dilute caustic soda then to mix the cellulose thoroughly with semi gelatinous form of copper hydroxide. The right proportions of copper ammonia and cellulose are necessary if the cellulose has to dissolve eventually as a spinning solution. These proportions are approximately, 4 percent copper, 29 percent ammonia and 9 to 10 percent cellulose. The free liquid is pressed out and the mass washed with water, which does not affect the copper hydroxide that is left on the cellulose fibres. The mass is then squeezed through a metal sieve and placed in a vacuum tank where all air is removed to prevent oxidation during the next ripening stage. The air free mass is mixed with ammonium hydroxide and left to ripen for 24 hours. During this stage, Schiweitzrs reagent, a dark blue solution is formed by reaction between the ammonia from the hydroxide and the copper hydroxide deposited on the cellulose. The mixture dissolves the cellulose and forms a thick viscous fluid that is the spinning solution (Figure 7.2). 86

95 The Non-Thermoplastic Man-Made Fibres - Rayon Figure 7.2 The spinneret used is made of nickel and has larger holes than those used for viscose. In addition to the spinneret the apparatus consists of a long glass funnel with a glass nippled end, a source of constantly running soft warm water introduced at a top area of the funnel and a coagulating trough containing a weak acid solution. From the coagulating bath the filaments are wound on bobbins or collected in spinning pots for final washing and drying, or may be carried on through a recently developed continuous process for these final treatments. Properties The microscopic appearance is different from that of viscose rayon. Rest of the properties are the same. When seen through the 87

96 Natural and Man-Made Fibres microscope in cross-section, cuprammonium fibres appear as tiny, smooth featherless circles. White cuprammonium does not yellow with age because it has traces of copper remaining, it is more resistant to mildew and mould than other cellulosic fibres. Figure 7.3 Uses Cuprammonium rayon is used for sheer dresses and curtain fabrics, for tricot lingerie and hosiery. It is blended with silk and with cotton. 88

97 Chapter 8: Man-Made Fibres M an-made fibres were first made experimentally in Europe in Commercial production of man-made fibres began in the United States in Production of a new fibre is a long and expensive procedure. First, a laboratory research program is set to discover a new material. When a promising material is made it is patented to give the producer exclusive rights to the process for a period of 16 years. Laboratory procedures must then be converted into large scale production. This is usually done in a very small plant called a pilot plant. All the man-made fibres have some processes in common. They have been produced commercially from non-fibrous material, or if fibrous to begin with, have somewhere in processing lost their fibrous nature and must then reform into fibre must then coagulate or harden within a reasonable amount of time after being extruded from the spinneret. After leaving the spinneret the fibres must be wound on bobbins or cones or are deposited in pots as cakes of yarn. The man-made fibres are divided into two groups: non-thermoplastic and thermoplastic. The non-thermoplastics form several subgroups, the largest group being of cellulosic origin, all of which are identified as rayon. The non-thermoplastic fibres except for the mineral fibres may be cared for much as cotton, linen, silk, or wool whichever they most resemble, in their visible characteristic and their reaction. They are not softened by heat, so they do not melt on ironing. As a group they are absorbent, pliable, comfortable, to wear, do not pill, do not accumulate static electricity and are not subject to attack by moth. In longitudinal look under the microscope they all look alike.

98 Natural and Man-Made Fibres Heat Sensitive Fibres Acetate Modacrylic Vinal Nylon Nytril Vinyon Polyester Olifin Spandex Acrylic Saran Although all the eleven fibre families differ in chemical composition and structure, they are grouped together because they have many common properties of which heat sensitivity is the most outstanding. These fibres are also referred to as synthetic or thermoplastic, or chemical fibres. Heat sensitivity is that property of a fibre that causes it to shrink, soften, or melt when heat is applied. These properties are not common with cellulosic or protein fibres. The fibres differ in their degree of heat sensitivity and even within a family the individual types may vary. For example, Orlon 38 type will shrink 20% or more when heat is applied. Whereas regular orlon has very little shrinkage. This high shrinkage property is used to advantage in factory process to create bulky yarn or to give three-dimensional effects in pile and upholstery fabrics. To create these effects blending is done with low shrinkage fibres. On applying heat these heat sensitive fibres cringe to give a buckle appearance. Fabrics made from heat sensitive fibres were at first considered difficult to stitch. But as compared to wool less work was required to sew these fabrics. They just required some different techniques. Nylon, for example, resists crease so it should be top stitched or edge stitch the crease. When sewing nylon lower temperature is required. Use very light pressing on seams. Use soft pressing pads to prevent glazing. 90

99 Man-Made Fibres Seam pucker which is caused by higher elasticity of the fabric or by nylon thread, must be controlled by changing the tension and stitch size. The needle should be smaller in size. Do not mark the fabric with waxy chalks it leaves an oily mark on the fabric which is difficult to remove. Heat setting Heat setting is defined as a heat treatment that gives shape and size that will not change under conditions of intended use. The heat used for setting must be higher than any temperature that will be used later. Since higher temperature than that will cause the fabric to loose off its set. Heat setting may be done on the yarn, fabric or completed article. Heat setting before scouring prevents wrinkles during scouring. All heat setting is done before or during dyeing. During the heat treatment the yarn or the fabric, or garment must be held in shape in which it is to be set. It must be allowed to shrink to some extent during setting or there will be possible future shrinkage as the molecules readjust themselves to their original unstretched condition. Heat setting is done in boiling water, in a steam oven or hot air. The time of treatment and the degree of heat determine the success of the process. Interestingly fabric effects are achieved by combining or altering heat-set and non-heat-set yarns in fabric. The thermoplastic fibres have a lot of properties in common. They are relatively non-absorbent and hygroscopicity is low, therefore they are uncomfortable to wear in hot climates, particularly if closely woven or knitted. They are easily washed and quick drying. They tend not to stain easily. The water soluble stains wash out readily. This is not always the case with oil bound stains. Because of low moisture absorption and non-conductivity or 91

100 Natural and Man-Made Fibres none at all, when conditions are right the thermoplastic fibres accumulate charges of static electricity and their accompanying annoyances. Most of them have excellent wrinkle resistance. Because of low absorption, new classes of dyestuff and new methods of dyeing have had to be developed for most of these groups of fibres. Seam fraying is about the same problem as it is in silk and other man-made fibres. In some instances however seam edges may be heat sealed on thermoplastic fibre fabrics. The thermoplastic fibres as seen under the microscope have all the same longitudinal appearance as other man-made fibres with no distinguishing characteristic for the different fibres. All these fibres are immune to the attack of mildew and moth, moulds. They are also non-allergic to human beings. Pilling Static electricity also tends to cause the picking up and retention of lint and dirt which may be held in pills giving a garment a soiled and rough appearance. Staple fibres are more subject to pilling than filament fabrics because the number of exposed fibre ends is so much greater. Texturizing processes reduce the problem of pilling. Static electricity Static electricity is generated by the friction of fabric rubbing against itself or against other objects. If the electrical charge is not conducted away, it tends to build up on the surface. Then when the fabric comes in contact with a good conductor, the shock or rapid transfer occurs. This transfer may produce sparks that in gaseous atmosphere may prove to be hazardous and can cause explosions. This is always a hazard in hospital operating rooms. Nurses are forbidden to wear nylon or acetate uniforms in operating rooms because of danger from ether fumes. 92

101 Man-Made Fibres People who live in areas of extreme cold and dryness find it particularly annoying since it is increased under these conditions. Static electricity causes soil and lint to cling to the surface of the dry fabric and dark colours become very unsightly. Brushing simply increase the difficulty. The resins used for crease resistance. Nylon Nylon is a generic name applied to a number of related products. Nylon 6,6 was produced by the DuPont Company. It is a manufactured fibre in which the fibre forming substance is any long chain of synthetic polyamide having recurring amide groups as an integral part of the polyamide chain. Nylon is composed of carbon oxygen, hydrogen and nitrogen as are the protein fibres. But since it is not made of amino acids its properties are not like that of silk or any protein fibre. In chemical structure, it is composed of long straight chains with neither side chains nor cross-linkage. Thus, the chains pack closely together In the fibre, accounting for its smooth rather slippery quality. Figure

102 Natural and Man-Made Fibres Nylon is polymerised by condensation reaction, under pressure of adipic acid and hexamethylene diamine. The molecules of the two substance hook together alternatively (copolymerisation) that is a molecule unit of acid and a molecule unit of diamine, with the elimination of water. The following formula demonstrates the polymerisation of a unit molecule of nylon. Many such units make up the nylon molecule. The process is controlled carefully to stop polymerisation within a narrow range, or the chains would become too long to possess the characteristic desired in a textile fibre. From polymerisation to cold drawing there are several steps in the production of nylon. The acid and the amine are put together in a huge kettle equipped with a stirrer, which mixes thoroughly, forming a salt, then the mixture and some water are fed into an evaporator where the solution is dried to a desired consistency and concentration of the salt. The concentrated salt solution is fed into a jacketed autoclave where a sequence of high temperatures and pressures induce copolymerisation of the two materials to molecular chains of the desired length. The water evolved from the autoclave is removed by evaporation. Nitrogen is bubbled through the autoclave to ensure that air does not get in and the newly formed nylon gets exposed to oxygen. From a slot at the bottom the molten nylon resin is extruded in the form of a thick, white, translucent ribbon and a spray of water cools the ribbon and causes it to harden as it is carried away from the autoclave to a casting wheel. The ribbon has an appearance similar to white taffy and is quiet hard. The next step is to break the ribbon up in to small pieces in a chipping unit, ready for forming into fibres. The process for spinning nylon is melt spinning. 94

103 Man-Made Fibres Figure 8.2 Nylon is composed of carbon hydrogen, oxygen and nitrogen as are the protein fibres, but since it is not made up of amino acids its properties are not like those of protein substances. In chemical structure it is believed to be composed of long straight chain molecules with neither side chains nor cross-linkages. Thus, the chain pack close together in the fibre accounting for its smooth slippery quality. Nylon 6,6 is produced from an acid and a diamine which has in turn been produced from other material actually going back to petroleum and coal tar derivatives. Nylon is polymerised by condensation reaction under pressure of adipic acid and hexamethylene diamine. The molecules of the two substances hook together alternatively (copolymerisation) that is a molecule unit of acid and a molecule unit of one diamine then acid again and so on repeatedly with the elimination of water. Many such chains makeup the fibre. The process is controlled carefully to stop polymerisation within a narrow range or the chain would become too long to posses the characteristic desired in a textile fibre. 95

104 Natural and Man-Made Fibres Figure 8.3 Cold drawing is the process that gives nylon many of its qualities for which it is most noted, that is great strength, toughness, elasticity, abrasion resistance. Drawing is carried out as for other fibres by passing the filament over rollers which revolve at different controlled speeds. Nylon is drawn three to seven times its original size. Drawing orients the molecular chain in the direction of the fibre axis, lines the chain up parallel to each other and permits a high degree of crystallinity of the fibres. Crystallinity tends to give a rigid structure to the fibres. Despite drawing the nylon fibre still retains greater elasticity than most other fibres. After drawing, nylon may be given an oil or antistatic spraying, twisted and heat set before being wound on the bobbins for weaving knitting or lacing. Heat setting is necessary to stabilize nylon in shape and dimensions. Nylon may be stabilized yarn, as woven or knitted fabric or as a knitted garment. Properties Nylon has a somewhat cool clammy feel in filament form. Some people like this feel and others dislike it as much. Nylon is lustrous, white fibre, transparent to translucent, that can in common be made in varying diameters, lengths and degrees of 96

105 Man-Made Fibres abrasion resistance and lustre. Its translucency has led to dissatisfaction at the consumer level. Nylon is both tough and pliable. Nylon does not flame readily, but burns slowly or fuses and drops off if flame is applied to it. It burns with the odour of cooking green beans or celery and as it burns or melts forms a waxy roll along the edge which becomes hard and tough as it cools. Regardless of the colour of the nylon fabric the curled, waxy edge is a light tan colour after burning. Although nylon may be termed non-flammable, the fusing and dropping off present a great hazard in many ways. Finishes may change this quality of nylon as it does for other fibres. Nylon is potentially the strongest of fibres. The wet strength of nylon is 85% of dry strength. Elongation is 18 to 37 percent. Nylon has a specific gravity of 1 to 1.4. Absorbency is low. Hygroscopicity is 4 percent. The low hygroscopicity amounts to accumulating static electricity. Nylon is somewhat rigid and does not drape as well as the acetates or silk. It is quick drying. Does not stain readily, it tends to pick up colour grease and soil in laundering with other garments, therefore white and pastel nylon needs separate laundry. Nylon is not affected by cold temperature but looses strength and yellows at sustained high temperatures. Ironing should be done at low temperature to prevent softening, glazing or melting and eventual discolouration. Nylon possesses a fair wrinkle resistance and crease recovery. It has excellent abrasion resistance, because of its strength and elasticity it is considered a very durable fibre. Nylon is degraded by exposure to sunlight, it leads to considerable loss in strength in a short time. It is very less sensitive to light degradation than silk. 97

106 Natural and Man-Made Fibres Acetate Acetate is the second of the man-made fibres produced by DuPont. Cellulose is the base material for the preparation of acetate. In addition to purified cellulose, the production of acetate requires glacial acetic acid, acetic anhydride, sulphuric acid, acetone and water. Figure 8.4 The purified cellulose is pre-treated by moistening with acetic acid in order to start reaction before the acetylation process begins. The acetylators are huge closed system mixing tanks equipped with a stirrer and jacketed to permit circulation of liquid or air 98

107 Man-Made Fibres around them so that the temperature can be controlled at the range of 35 to 120 F. Exact amount of acetic anhydride, glacial acetic acid and sulphuric acid are put in the acetylator, mixing and cooling to about 45 degrees. Then the moistened cellulose in amounts of 200 to 300 lb. is added gradually with constant kneading by the stirrer blades. The temperature is held below 68 F for an hour and then held below 86 F for the rest of the acetylation period of 5 to 8 hours. During acetylation the fibrous structure of the cellulose has disappeared and the mixture has become transparent, acrid smelling, viscous fluid having the smell of molasses. From the acetylator the viscous triacetate is run into tanks containing water and weak acetic acid. The mixture is allowed to stand for 20 to 50 hours for partial deacetylation. At this stage the viscous fluid is run into water, which precipitates the secondary acetate as white crumbs like flakes. The flakes are washed thoroughly in huge vats In order to remove and recover all remaining acetic acid. Dry spinning is done to procure acetate. Then it is passed through spinnerets.the difference in speed between winding of the bobbins and emergence of fibres, helping to control diameter, orient the molecules and increase fibre length. When drawn from the spinneret acetate is a finished fibre needing no further processing except lubrication as it is wound on the bobbin. Properties Acetate has a soft, smooth, cool, pleasant feel. It is rich in appearance and has excellent draping characteristics. Acetate is pure white in colour, and yellows only slowly with age and use compared with silk, wool and rayon. 99

108 Natural and Man-Made Fibres Acetate melts or burns depending on the weight and construction of the fabric. The absorbency and hygroscopicity of acetate are lower than that of other fibres. The specific gravity is It is considerably weaker when wet than dry. It is heat sensitive. Acetate dissolves completely in acetone, and this is a commonly used method for identifying the fibre quickly. Uses Acetate is used in dresses, blouse, lingerie, bathing suit, sports wear, gloves, ties and robes for men and all kinds of garments for babies. Glass curtains, draperies, blankets, bed spreads, comforters and rugs. Acetate is used for cargo, parachutes and all sorts of fluorescent dyed fabrics for signals, safety targets and identification. Mineral Fibres Glass Glass fibres are inorganic polymers based on silicon rather than carbon. Making of glass textile fibre has developed largely since When the processes were developed for mechanically drawing the fibre out into fine enough filaments to enable the yarns made from them to be folded, woven and knotted without breaking. The U.S. produces and uses most of the glass fibre in the world. In 1958, the leading countries were U.S., France, Japan, Canada and Sweden. The raw material for glass fibre is sand, silica and limestone, combined with additives of feldspar and boric acid sand is the 100

109 Man-Made Fibres main ingredients. Sand suitable for glass making should be high in silica and low iron and other undesirable impurities. The raw material are placed in a batch furnace at a temperature of over 300 F where the ingredients melt and form a colourless, transparent, homogenous, viscous liquid, which is the molten glass. Until recently the molten glass has been dropped. In small amounts to form clear, greenish coloured marbles and these were later melt spun. Figure 8.5 Formation of the fibre from marble is simple as can be seen from the diagram. The marbles are placed in a small furnace 101

110 Natural and Man-Made Fibres (hooper) in which a temperature of 2500 F is maintained, above the spinneret device and winding equipment. As the marbles melt and gravity forces the molten glass to flow downwards into the brushing box, the bottom of which has more than 200 tiny holes. The bottom of the brushing box with its holes serves the same purpose as spinneret. As the molten streams of glass emerge into the air, they begin to congeal, a sizing or other binder material is applied to prevent abrasion, and they are wound into a tube. They then pass through a lubricating spray and fall onto a rotating drum, forming a thin gauge like sheet. Drawing the fibres into very fine diameter is essential in order to obtain the flexibility necessary for a textile fibre. Coronizing Glass fibre and yarns are handled in processing fibres. This finishing process is called coronizing. The first part is a heat treatment of 5-20 seconds duration at 1200 F in a furnace for 3 purposes: (1) Burning off the lubricants or binder applied in drawing. (2) Relaxation of tensions due to yarn processing and weaving. (3) Relaxation of tension due to yarn. After leaving the furnace it should be given an abrasion resistance finish. This is usually one of the thermoplastic resins which will form a protective coating around the glass fibre. Pigments are added for colour. Properties (1) Diameter is microns. (2) It is the strongest of most man-made fibres. (3) Brittle and lacks pliability. 102

111 Man-Made Fibres (4) It is non-absorbent and non-hygroscopic. (5) It is water repellent and has a specific gravity of (6) It is subject to severe abrasion, and cuts each other if they rub together. (7) It is colourless, resistant to acids, alkali and each other compounds. Uses Drapery, curtains, tablecloth, lampshade, fire dust, iron board cover, insulating electrical wires, parachute. Asbestos (Fireproof, Acid Resistant, Low Pliability) The fibre found by mining or quarrying these mines are blasted free. The fibre is carefully separated from the crushed rock and sorted according to fibre length properties. It is 3/8 inches to 3/4 inches in length and having a small diameter. Under the microscope the fibres looks like tiny polished rods, very straight with no rough surfaces. The physical structure of the fibre makes it difficult to spin, into yarn because it lacks length and cohesiveness. Asbestos is white or greyish in colour. Asbestos fibres do not take dye readily. Asbestos is used for padding, laundry presses and mangles belting for conveying hot material, brake lining, gloves and aprons. It is absorbent and has wicking properties. 103

112 Natural and Man-Made Fibres Asbestos does not dye readily and colour is likely to be spotty and have poor fastness. It is used for flame proof clothing of many kinds of laboratory, industrial and military purposes. It goes into all types of protective equipment for fire fighting, fire screens, fire blankets, insulation for steam and other hot pipes. Asbestos is sometimes used with glass to create beautiful drapery for hospitals, theatre, libraries, schools and other building. 104

113 Chapter 9: Polyesters D Dacron acron was the first polyester fibre introduced in Exclusive patent was given to DuPont Co. of England. It is a long chain polymer composed of 85% by weight of an ester of dihydric alcohol and terephthalic acid (p-hooc-c6h4-cooh). Dacron found immediate acceptance in easy care, wash and wear garments such as tricot blouses and men s shirts. Comfort properties were improved by blending cotton in Dacron with 65% Dacron and 35% cotton. In 1959, three new polyesters hit the market. Fortrel: Formerly known as teron, is produced under license by fibre industries. Vycron: It is produced by Beunit Mills and Co. Kodel: The third fibre was developed by the Tennessee Eastman Co. and is fundamentally different from other polyesters so no license arrangement was needed. Manufacture The manufacturing of polyester fibres is quiet similar to nylon. Both fibres are melt spun. Ethylene glycol and terephtlalic acid are polymerised at high temperature in a vacuum kettle. The polymer is a pasty substance which is extruded as a ribbon and cooled on a casting wheel as a white porcelain like substance. The ribbon is put through a chipping unit, dried and led into a hooper. The polymer is solidified and cut into cubes which are melted and spun into fibres. The fibres solidify in air and they are then hot stretched to orient the molecules and reduce the denier of the fibre.

114 Natural and Man-Made Fibres The fibre is heat set before use. Polyester fibres are produced in filament and staple form in bright and dull lustres in regular and high tenacity strength and can be solution dyed. The molecule unit of Dacron is heavy stiff and resilient. They resist bending but recover from bending quickly. The molecule chains are held together by numerous bonds of such a nature that they cannot be relaxed by moisture, hence the fabric has good wrinkle recovery. Appearance Figure 9.1 The fibre has a smooth rod like shape which is typical of melt spun fibres. Dacron 54 has a ribbon like shape which blends better with cotton. Dacron 62 has a trilobal shape which is similar to silk. Although nylon and the polyesters burn alike in some ways they can be distinguished in some ways by the odour and smell with which they burn. Both are relatively non-flammable in the unfinished state. Both form tan beads when the melt hardens. Some dyes may however cause a darker bead to form. Polyesters have an aromatic odour, and a dark black soot. Nylons odour is celery-like and the smoke is white. Dacron type 62 is trilobal with a silk like appearance. It is more susceptible to acids and alkalies and dyes more readily than other regular Dacron. The man-made fibres lacked the unique combination of aesthetic properties of silk. Dacron and nylon achieved that goal. The processing of Dacron was changed to finish that goal. Manmades are processed under tension by a continuing process rather than a batch processing method. The Dacron fibre was processed 106

115 Polyesters under very relaxed conditions. Finishing started with a heat setting process which stabilizes the fabric to control width, removes any wrinkle and imparts resistance to creasing. The caustic soda treatment is given. In this treatment, part of the fibre gets dissolved away like serecin of silk. As a result the fabric structure is more mobile. To get weave crimp, the remaining finishes of bleaching, colouring, washing and a final heat setting is done to fix the colour and assure stability and are all done with the fabric under completely relaxed conditions. The trilobal shape has resulted from the shape of the holes in the spinneret. Melt spun fabrics posses the ability to retain shape of the spinneret holes. Figure 9.2. Cross-section of Dacron. Dacron has found usage in bedding, furniture, pillow fillings. It can be sterilised, so it has found usage in hospital bed fillings and pillow fillings. Properties Pilling is a common problem with Dacron fabrics. They require blending with cotton and also finishing treatment to combat the pilling problem. 107

116 Natural and Man-Made Fibres Singeing is the most sought after finishing method to burn of the linters on the surface of the fabric. The double flame burns off the fuzz giving the fabric a neat appearance. When cooled the fibres are set and locked in the yarn and the fabric structure. Both treatments improve the hand and heat-setting improves drape and wash and wear performance. Dacron is an opaque white fabric with high strength and elongation of 20 to 48%. The specific gravity is 1.38, because of its strength it can be drawn into a very fine fabric with fine diameter. It can make very sheer fabrics. The polyesters are more electrostatic than other fibres and hence they attract more dirt quickly giving an untidy appearance. Colour crocking is another disadvantage with many printed Dacrons. Dacron has an affinity for oil. The collar of the garment absorbs so much oil and grease that when it is washed the colour of the collar also faded rendering the garment unuseable. Dacron has however been popular in curtains because it has good light resistance. Wicking is a property that makes Dacron quick drying and easy to maintain. Dacron melts at 480 degrees. It has a good resistance to some of the weak acids even at boiling temperature. It is degraded by concentrated sulphuric acid. It is not affected by bleaches. Orlon The term Orlon refers to all types of acrylic fibres and not to any single product or process. Acrilonitrile polymer are the raw material used for the production of Orlon. Orlon is considered the most silk like synthetic fibre. Orlon is synthesized by addition type Figure 9.3 polymerization with one entire unit of acrilonitrile hooking to the next entire unit and no condensation products to be disposed off. It has been theorized that about 2000 such units combine to make Orlon. Orlon does not have side chains in the fibres. But there are 108

117 Polyesters numerous hydrogen bonds between adjacent chains in the fibre accounting in large measure to stability and inertness to chemical reaction. Orlon staple fibre has also wool like properties. At the same time inherent properties make it outstanding in the industrial field. The combination of properties of Orlon result in a fibre most suitable for certain purposes other than nylon and Dacron. Acylic fibres are produces by two companies and marketed under the trade name of Acrilan, Creslan, Orlon and Zefran. These fibres contribute to about 20% of the non-cellulosic man-made fibres available in the market. Probably the most outstanding qualities of these is its high resistance to heat, extreme sun-light, and also to smoke and acid fumes. It has high tensile strength, resistance to mildew, moth and insects. Figure 9.4. Flow chart for Orlon production. The surface of Orlon is serrated. The cross-section is dumbbell in shape. They are widely used in men s, women s and children s sweaters. In this field, their high bulk, resiliency and easy care make them superior to all other man-made fibres. Acrilan has been very useful in carpeting because of its resiliency and good resistance to abrasion. Properties common to all acrylics: Low density - Fabric feels light and airy. 109

118 Natural and Man-Made Fibres Low to medium strength - Satisfactory. Differential shrinkage and good recovery - Warmth, good cover maintains loft. The fabric has high bulk. Excellent resistance to weathering - It is good for outdoor furniture. Low moisture absorption and wicking - Quick drying, easy spot removal. Thermoplastic - can be heat set. Durable pleats. The fabric has good dimensional stability. Resistant to insects and mildew - No storage problem exists for Orlon, it is not attacked by insects and mildew. Acrilan The process of manufacturing Acrilan is more or less the same as that of Orlon. Acrilan is a copolymer of acrylonitryl and vinyl acetate, although some other substances may replace a part of the latter material. The polymer is a white powder which is centrifuged and then dried in a heated revolving drum after polymerization. The spinning solvent is dymethyl acetamide. 110 Figure 9.5. Cross-section of Acrilan.

119 Polyesters Acrilan is wet spun with equipment similar to that used for the spinning of rayon. Drawing temperatures are not specified. After drawing, the fibre is crimped cut into staple length and baled for shipment. Properties Acrilan has a specific gravity of 1.17, strength similar to acrylic. The strength, absorbency, hygroscopicity, lightweight, with warmth and high covering power are similar to those properties in Orlon. Acrilan does not have the cashmere like softness of Orlon and is less sunlight and weather resistant. It has excellent wrinkle resistance and crease recovery. It has a crisp, springy and wool like hand. Creslan Like other acrylic fibres it contains substances other than acrylonytrile to give it a better affinity to dyeing. It is produced in deniers from 2 to 15 and in length from 1¼ to 6 inches. It is available in bright and semi dull lustres and is crimped mechanically. Figure 9.6. Cross-section of Creslan. 111

120 Natural and Man-Made Fibres Uses Uses of Creslan is also similar to that of Orlon and Acrilan that is to say in sweaters, other knitted goods, fur like fabrics, blankets, and other items for which bulk, warmth, and lightweight are desired. It is used for raincoats, suits, jackets, dresses, and children s outerwear. Zefran Zefran is also composed of acrilonitryl and limited amount of other substances. Zefran is made of material which might be expected to copolymerize, the way in which the substances have been induced to join in the molecular chain are unique. This results in a chain backbone structure of acrilonitryl with other substances hooked on as a side chain type tail. The tail material is highly dyeable and absorbent, resulting in a Zefran fibre with some of the advantages of a thermoplastic and non-thermoplastic fibres. Figure 9.7. Cross-section of Zefran. Zefran resembles the acrylics in most of its properties although the unique structure results in some differences. Its specific gravity is 1.19, tenacity is average 3.4 gms/denier, strength can be varied from relatively low to high, and wet strength is about 95% 112

121 Polyesters of dry strength. It is slightly less heat sensitive than acrylics. Elongation is about 30%. Hygroscopicity is 2.5 %. It is wrinkle resistant, dimensionally stable and washable. Zefran is white in colour and has a round cross-section. It can be heat set and is said not to pill. It is soft, warm, comfortable and drapable. Because of its absorbent tail Zefran can be dyed by conventional methods with most of the dyestuffs used for the fibre. Modacrylics Dynel Dynel is a copolymer of 40% acrilonitrile and 60% vinyl chloride, processed in the same way as in acrylic. Polymerization takes place in the same way in an autoclave under controlled heat and pressure. Acetone dissolves the Dynel resin: air is exhausted in a vacuum tank before spinning. The viscous solution is forced through metered pumps and through spinnerets, and the fibres are coagulated in a water bath. After drying, the filaments are hot drawn to as much as thirteen times of their original length to orient the molecular chain. Fabrics are later heat set to relax strain and tension within the yarn in order to give good dimensional stability. Figure 9.8. Cross-section of Dynel. 113

122 Natural and Man-Made Fibres Properties It has a specific gravity of 1.30, one of the most heat sensitive fibres. It has good covering power and insulative ability with fairly lightweight. Hygroscopicity is 0.4%, dry strength is 95%. Excellent winkle recovery. Hot water deluters Dynel. It is resistant to most chemicals, but dissolves in acetone and other ketones. It can be dyed readily with number of dye stuff, in a wide range of colours. It may also be solution dyed. It is resistant to perspiration. Uses It is brought into use for apparel and house hold furnishing such as dresses, fleece coats, sleeping garments, sportswear, men s summer hats. Chemical resistant clothing is one of its most important industrial uses. Dynel is used for making wigs, doll hair which can be washed and set in a particular style and also redyed. Verel Verel is a copolymer of acrylonitrile and other unspecified compounds. Its method of processing is not known. Verel is produced in three degrees of stability which is apparently due to differences in heat treatment and method or extent of drawing. It is also prepared in two degrees of flammability. 114 Figure 9.9. Cross-section of Verel.

123 Polyesters Properties Relative hygroscopicity of Verel is 3.5 to 4%, which is higher than most thermoplastic fibres. And it makes wearability more comfortable. It is also less subject to static electricity problem. It is extremely flame resistant. It has good resistance to weather deterioration. A maximum safe temperature is 300 F. The chemical resistance of Verel is high. It can be easily dyed and is stain resistant. Uses It finds usage in fur like pile fabric for coats, coat lining collar, and other trims. It is also used in carpets and rugs. The Nytrils Darvan Darvan is a co-polymer of about equal amount of vinyl cyanide, called vinylidene nitrile and vinyl acetate that copolymerize in the molecular chain. Polymerization is done in autoclave kettle at a temperature of 115 F. The polymer is precipitated. It is then dried and subsequently dissolved for spinning with dimethyl formamide. Spinning is done through a spinneret into a coagulating water bath. The filaments are heat stretched and drawn, given antistatic treatment and cut into staple length for use. Properties The specific gravity of Darvan is It is creamy white in colour, soft and warm to touch. Its strength and elasticity are medium. Elongation is 30% and it is resilient and wrinkle and shrink resistant. Hygroscopicity is 2-3%. It does not pill. Darvan has excellent weather resistance. It is less heat sensitive than acrylic. It can be bleached with hypo-chloride. 115

124 Natural and Man-Made Fibres Uses It is most commonly used for washable sweaters and other soft knitted goods. It is also used as blends for many types of fabric. The Sarans Vinilidine chloride, vinyl chloride and a catalyst are mixed in a reactor kettle and heated to obtain the basic resin powder. The resin is then melted by application of heat and extruded through heated spinnerets and coagulated in a water bath in such a way as to cool it before Figure 9.10 crystallisation can occur. This is also called quenching. Then the fibre is immediately stretched to about four times its original length to orient the molecular chains within the fibre, to increase the strength and toughness and to give fibres the desired fineness. A pigment is added to the melt before extrusion if colour other than pale yellow is desired. Properties Saran is smooth fibre with round cross-section, and a specific gravity of Strength, toughness and elasticity are controlled by the stretching process and are considered good. Saran does not absorb at all. Abrasion resistance is good. Saran is stain and soil resistant and can be easily cleaned. It will soften and char when exposed to flame. It cannot be dyed. Uses Saran is utilised for apparel accessories, furnishings and industrial items. It is also used for auto upholstery and seat covers, luggage, carpets and rugs, wigs, doll hair, outdoor furniture, domestic upholstery and drapery. 116

125 Polyesters Rubber Rubber is not a true thermo-plastic fibre, it is heat sensitive and requires much the same care as thermo-plastic fibres. Process Latex, the milky sap of the rubber tree is mixed with specific quantities of some other not so well known chemicals to prevent air and light deterioration, extruded through fine porcelain tubes which perform the same function as spinnerets for the other manmade fibres, then vulcanised in a special vulcanising oven. Radiation is being used in place of vulcanising for curing some rubber products. The rubber fibre form the core for lastex yarns. They can be dyed in pastel colours. After curing, the rubber fibre is put through a bath of fine talc to facilitate handling. In the process of covering the core with cotton, rayon, nylon or other fibre yarns the elasticity and resiliency of the resulting lastex yarn can be controlled to varied degrees of stretch and recovery. These processes result in elastic yarns fine enough to be knitted, woven and made into lace on conventional machines. Properties It is highly elastic. Properties of absorbency, comfort and hand depend largely on the fibre used in covering the rubber core. Lastex is heat sensitive and will deteriorate at high temperatures. Uses The many uses of lastex include women s foundation garments, elasticised shoe fabrics, elastic hose, surgical bindings, swimsuits and shirring yarns for machine shirring. 117

126 Natural and Man-Made Fibres Spandex Spandex is a manufactured fibre in which the fibre forming substance is a long chain synthetic polymer of at least 85% of segmented polyurethane. Two elastomeric fibres were discovered in late They are Lycra and Vyrene. Both were trademarked fibres of the DuPont Company. Lycra All the processes and raw materials have not been reported, it is said to require more complex chemical reactions than the other fibres produced by the company. Lycra was formerly known as Fibre K. Lycra is produced in monofilament form. Properties listed for Lycra are white colour, dull lustre, high strength, good abrasion resistance, sticking temperature is 347 F and melting temperature is 482 F. Since Lycra is white in colour, it does not need to be covered with other fibres and can be knitted either covered or uncovered. Lycra is soluble in boiling di-methyl formamide. It is said to be easily dyed and possess high resistance to perspiration and cosmetic oils and lotions. Lycra is also expected to find usage in surgical stockings, athletic uniforms and swim wear. Vyrene Vyrene serves the same purpose as Lycra, but somehow it is not so much in commercial production. 118

127 Chapter 10: Yarn Y arn is a group name for an assemblage of fibres laid or twisted together. The process of making yarns from fibres, tow or liquid material is called spinning. Figure Packaged for weaving or knitting. Yarns may be made and prepared through all steps ready for fabric construction, in the plants where the fibres are processed or produced. For each fibre, the process of making yarn is different. Yarn making is different for wool and different for balls of cotton which are tightly packed baled cotton.

128 Natural and Man-Made Fibres Processing of yarns There are many large intricate machines for yarn making. Somewhat different types of machines are required for wool, linen, cotton and silk. General processes The general processes done to the fibre before making a yarn are opening, picking, cleaning, blending, tinting, degumming, scouring, bur picking, carbonizing, cording, combing or hackling, drawing, spinning, winding, throwing, quilling, slashing and rewinding. Degumming Degumming is the removal of the serecin from raw silk. The silk is soaked in warm soapy water, the gum on it is dissolved then it is passed between parallel plates set closely enough to remove any adhering gum or other matter. Short fibres are carried away from degumming and made into spun silk. Scouring Scouring is the process used on wool to remove grease. Scouring operation is carried on with soap and ash at varying temperature to clear foreign material from wool. A chemical solvent in a closed system has been used recently, it results in a open mass of soft-textured fibre. But it has high cost. Bur picking and carbonizing These are also processes for wool. They are methods for removing bits of burs, sticks and other vegetable matters remaining in wool. Carbonizing is done after scouring, it is a treatment done by weak sulphuric acid or hydrochloric acid heating to F. 120

129 Yarn Opening and blending These two steps are carried on simultaneously and are necessary for cotton and wool. The steel bands holding cotton should be cut and cotton lifted out in quantities that can be opened up in fluffy masses in early operation. Wool comes from the scouring rooms after bur picking or carbonization, already fairly well opened. All groups must have large clumps of fibres picked up (this is called opening). Blending Blending is the mixing up of two different fibres of equal weight or width, to ensure uniformity. Blending is accomplished either by laying approximately equal amounts or exactly weighted amounts of the fibres from the various bales or bags in thin layers. Combing Combing is a process used to produce yarns for a limited number of fabric types in which smooth yarns of long fibres and with considerable twist are used. Drawing, spinning and winding These are various parts of the same process. From two to six card slivers or rovings are fed into the machine together to ensure further uniformity. Throwing Throwing is a process of what drawing, spinning and winding are to natural fibres. The further step of slashing is the adding of sizing material, such as starch, to warp yarn in order to give them body, smoothness and strength to withstand the stresses of loom or knitting machine operations. This treatment is not necessary for filling yarns. Quilling is filling of the small spindles or quills that fit inside the weaving shuttle. 121

130 Natural and Man-Made Fibres Simple yarns Simple yarns are composed of only one type of fibre and have the same diameter, smoothness and twist, all along their length. They are also defined by ASTM as self blended yarns. Blended yarns They are composed of two or more different types of fibres that have been blended in processing. Textured yarns These have complex structure. They are also called novelty yarns. They are produced by combining different yarns under different tension. A third fine yarn is used to secure the texture produced by the two main yarns. Examples of textured yarns are cork-screw yarn, gimp, truffle, diamond, knot, spot, node or nub. A cloth blanket with widely spaced warp yarns is woven, then the filling is cut between the warp yarns are brushed in the desired direction, or left unbrushed to form the caterpillar chenille yarn. Yarn twist Several fibres are twisted together in order to make yarns strong enough for weaving, knitting or the construction and also for durability in wear, and to give the type of surface to the fabric. A certain amount of twist improves strength but overtwisting decreases strength, and will itself break the yarn if over done. Warp yarns are given considerable twist and rigors of weaving and present as a frictionless surface as possible. Filling twist Filling twist may vary from zero of satins to the high degree of twist which may cause kinking for crepe fibres. 122

131 Yarn Knitting yarns Knitting yarns have little twist as soft texture is ordinarily desired. Yarns may be given a hard amount of twist for such fabrics as worsted twills, where the face of weave is visible. Although the direction of twist in yarn is of concern primarily to fabric producers. Direction of twist is defined by ASTM as S or Z as follows: When the yarn is held in vertical position, the spirals around its central axis conform in direction of slope to the central portion of the letter S and Z twist if the spirals conform in direction of slope with the central portion of the letter Z. S twist is a clockwise twisted yarn and Z twist is an anticlockwise twisted yarn. Figure 10.2 The direction of twist only matters in the construction of ply, cord and textured balanced yarn, and in construction of certain fabrics, such as crepes, in which tightly twisted filling yarns of alternate and equal numbers of S and Z twist yarns form the pebbles of the crepe, and prevent twisting of the fabric. 123

132 Natural and Man-Made Fibres Classification According to Ply Figure Diagram of single ply and cord yarn. Ply refers to the number of individual strands that make up a yarn, and the manner in which they are put together. The terms commonly used are simple ply and cord. A single (or one ply) yarn is a yarn composed of single fibres which if untwisted will separate into individual fibres, from which it was made. A ply or multiple yarn is made up of two or more single yarns. A cord yarn is made up of two or more ply yarns twisted together. Mostly singles yarns are used for making fabrics like gingham, flannel and satin. Cords are used for making stuff which requires more strength e.g. ropes etc. Complex single yarn These may be single or 2 ply. In the single, the yarns are left untwisted or slackly twisted at irregular intervals, in order to produce soft sections, in a 2 ply slub the soft and fluffy portion is held in place by a second that has more twist. Slub yarns are made from staple fibres. Flock yarns/flake yarns These are single yarns in which small tufts of fibre are inserted 124

133 Yarn at irregular intervals and held in place by the twist of the base yarn. It is used for fancy effect in suiting and dress fabric tweeds. Complex ply yarn Boucle yarn These are tight loops projecting from the body of the yarn at regular intervals, are of 3 ply construction fabrics by knitting or weaving. Loop and curl yarn It is of 3 ply construction. The base yarn is coarse and heavy effect yarn forms loops or curl, made of single or a ply of 2 or more singles. Ratine and gimp yarns The structure is same as other complex ply yarns. These have a rough surface appearance. Gimp yarns have the loops on the ratine yarn. They are soft but securely twisted yarns. Nub or spot and knot or knop yarns A nub or spot yarn is made on a special machine that permits the base yarn to be held stationary while the effect yarn is wrapped around it several times to build up an enlarged segment. In knot or knop yarn, brightly coloured fibres are frequently added to the enlarged knot. Seed or splash yarn It is the same as above but the shape of the enlarged knot segment of splash yarn is elongated and that of the seed yarn is tiny. Spiral or cork-screw yarns In this type of yarn, the effect is obtained either by twisting 125

134 Natural and Man-Made Fibres together yarns of different diameters or different fibre content or by varying the rate of speed or the direction of the twist. Spiral yarn has two or more single yarns of different sizes. Chenille yarn This resembles a caterpillar created special effects in fabrics with a pile like surface on one side of the final fabric. Core spun yarn In this, a base or foundation yarn is completely encircled or wrapped by a second yarn. Metallic yarn This is decorative. Complex yarns add texture and design to a fabric. Figure 10.4 Figure

135 Yarn Figure 10.6 Figure 10.7 Textured yarn A specific of yarns made by special types of manufacturing processes made from either filament or staple fibre. Different types of textured yarns are as follows: Stretch yarns These are with high level of elastic, extensibility and recovery. Modified stretch yarns These have some degree of stretch, but have been stabilised by processing to control the stretch. 127

136 Natural and Man-Made Fibres Bulk yarns These are designed to add bulk to the fabric. Most textured yarns are from the thermoplastic fibres. Heat setting It is the property of fibre for altering, modifying or influencing the characteristics of the fibre through the application of controlled heat e.g. pleat setting in nylon fabrics. Other type of yarn manufacturing Split film yarns These are made from sheets of plastic film or plastic tape that are cut into narrow ribbons which are stretched and the polymeric molecules break apart into fibrils. These fibrils are then stretched further to draw out the fibrils twist is added and the final yarn is made. The process is used mainly for olefins. Twistless yarn These are made from fibres that are held together by an adhesive. Self twist yarns These are 2 ply yarns. Two single yarns may be used, each is twisted with alternating directions in small segment. Fascinated yarns These are made from a bundle of parallel fibres that are held together by periodically having other fibres wrapped around the bundle to hold it together. Blending Blending is a complicated and expensive process, but it makes possible to build in a combination or properties which are 128

137 Yarn permanent. Not only blends are used for better functionality of fabric, but also they are used for beauty of appearance and hand. Two unlike strands of fibre may be twisted together as a ply making a combination yarn. Mixtures, combinations and blends give properties to fabrics that are different from those obtained with one fibre only. There is no perfect fibre. All fibres have good, fair and poor characteristics. Blending enables the technician to combine fibres so the good qualities are emphasised and the poor qualities are minimised. Blending can be done at any stage prior to the spinning operation. It can be done during opening-picking, drawing and roving. Opening-picking Several bales of fibre are laid around the picker and an armful from each bale is fed alternatively into the machine. Polymer blending The raw materials for orlon and acetate have been dissolved together as a single solution to make a fibre. This creates possibility of a whole new field of fibres. Blending is done for several reasons To improve spinning, weaving and finishing. Efficiency and uniformity of the product. To obtain better texture hand and feel. For economic reasons, expensive fibres can be extended by blending them with more plentiful fibres. To produce fabrics with better performance. To obtain cross dyed effect or create new colour combinations. 129

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139 Chapter 11: Finishing T he properties of a fibre can be changed completely by a finish. Pieces of the same fabric can be finished such that they bear little resemblance to each other. A finish is defined as anything that is done to a fibre either before or after weaving or knitting to change the appearance (what you see), the hand (what you feel) and the performance (what the fabric does). Fabrics have always been finished. The process of mercerisation being the oldest of the finishing methods. Finishing may be done in the mill where the fabric is constructed or it may be done in a separate establishment by a highly specialized group called converters. All fabric finishing adds to the cost of the fabric. Grey goods: Grey goods (grey, greige or loom state) are fabrics regardless of colour, which have been woven on the loom and have received no dry or wet or drying finishing operation. Mill finished fabrics are those which can be sold and used without converting although they may be sized or Sanforized before they are sold. Converted or finished goods are those which have received wet or dry finishing treatment such as bleaching, dyeing, or embossing. Finishes may be classified into: Temporary finishes Chemical finishes

140 Natural and Man-Made Fibres Mechanical finishes Functional finishes Some processes have to be carried on the fabric before imparting the finish. The fabric after it leaves the loom has impurities which interfere with the process of finishing. Desizing This is the process of removing the sizing of the warp yarns. A desizing substance sulphuric acid or an enzyme solubilises the starch which is completely removed during washing. Degumming or boiling off These are terms used to describe the desizing of silk. Silk is woven in the gum with serecin forming the protective layer for the silk filament. Boiling off consists of washing in caustic solution. Boiling off is also used as a desizing operation. Bleaching The principle involved in bleaching are the same. Bleaching cleans and whitens grey goods. The natural fibres are off-white in colour, because of the impurities they contain. Since those impurities are easily removed from cotton. Most cotton grey goods are bleached. Bleaching is also used to strip dye from fabrics which have been imperfectly dyed or need to be redyed. Kinds of bleaches Chlorine bleaches are efficient bleaches for cellulosic fibres but should not be used in concentrated solutions or at high temperature. Hydrogen peroxide (H2O2) is also a good oxidizing bleach. Sodium perborate is a powder bleach. It is a safe bleach for all kinds of fibres. 132

141 Finishing Singeing Singeing is the process of burning of all lints on the surface of the fabric. These protruding ends cause roughness, dullness, pilling, and interfere with finishing. Singeing is the first finishing operation for all smooth finished cotton fabrics. Singeing is usually done by a gas flame singer. The fabric is first run open width over a heated roller to dry it and then run on high speed through a gas flame and into a water bath to extinguish any sparks. A desizing agent is added to the water bath. Carbonizing This is the treatment given to wool yarn or fibre with sulphuric acid. The treatment destroys vegetable matter in the fabric and a more level desizing can be achieved. Carbonizing also gives better texture to all wool fibres. Temporary finishes These finishes stay on the fabric only till such time as it is laundered. These may also be called renewable finishes. These simple procedures can be renewed after each washing e.g. ironing, starching. Various starches are used for starching cotton garments like cornflour, arrowroot, sago, rice starch, gelatine, softeners, resins and cellulose solutions. Some bleaches which are either oxidising or reducing bleaches are also used as temporary finishes. Mechanical Finishes Calendering, pleating, beetling, decatizing, tentering and napping are some of the mechanical finishes which will be discussed in detail. Calendering Calendering is performed through a stack of rollers through 133

142 Natural and Man-Made Fibres which the cloth passes. Most calender machines have three rollers. (others have 2, 5 or 7). Hard metal rollers alternate with softer cloth wrapped rollers or with solid paper roll. The simple calender corresponds to the house hold ironers and gives a smooth finish to the fabric. The cloth is slightly damp when it goes into the roller. The metal roller is heated. The cloth travels through the calender at the surface speed of the rollers, so the rollers simply exerts pressure to smooth out the wrinkles. And give a slight sheen. Figure Simple calendering. The friction calender gives a highly glazed surface to the fabric. The cloth is first passed through the finishing solution and then dried to a certain degree of dryness. It is then threaded into the calender. The speed of the metal roller is greater than the speed of the cloth and the roller polishes the surface similar to the hand motion or the iron. The moire calender is an engraved cylinder. It has very fine lines engraved on the surface. When this roller is heated and the fabric is threaded through the rollers. The hot metallic roller passes on these engraved lines upon the fabric. 134

143 Finishing The schreiner calender has a metal roller engraved with 200 to 300 fine diagonal lines which are visible only under a hand lens. The primary purpose of this finish is to produce a deep seated lustre, rather than a shine, by breaking up reflectance of light rays. It also flattens the yarns to give a smooth appearance and a good cover. It can upgrade a sleazy material it was originally used for cotton sateen and table damask. Figure Schreiner calender. Pleating Pleating is a variation of embossing. The machine pleating method is most frequently used. The machine has two heated rollers. The fabric is inserted between the rollers as high precision blade puts the pleats in place. A paper backing is used under the pleated fabric and the pleats are held in place by paper tape. After leaving the heated roll machine, the pleats are set in an aging tank. The heat sensitive fibres especially nylon take permanent pleats. Chemicals are added to cotton and wool to make them hold durable pleats. 135

144 Natural and Man-Made Fibres Beetling Beetling refers to beating or hand pounding of a fibre. This was a process which was initially a hand operation. It is now mechanised. As the cloth revolves on a slow huge wooden drum. It is pounded with wooden block hammers. The pounding may continue for a period of 30 to 60 hours. It flattens the yarn and makes the weave appear less open than it really is. The increased surface area gives more lustre, greater absorbency and a smoothness to the fabric. Beetled fabrics are softer than unbeetled fabrics. All linens are not beetled. Only linen for shirting, other apparel and table linens are beetled. Tentering This is one of the final finishing operation which straightens and also dries the fabric. The fabric is put through a tenter frame. The filling threads are put at right angles to the lengthwise yarns. This device may be a hand-controlled one or it may be one controlled by an electronic eye. These straighteners are called weft straighteners. There are two types of straighteners. The pin tenter and the clip tenter. The small pin size holes that we see on the fabric selvedge are the marks of a pin tenter frame. Figure Tenter frame. Decatizing This finish is used to produce a smooth wrinkle free and lofty hand on woollen and worsted fabrics and on blends of wool and 136

145 Finishing man-made fibres. The process is comparable to steam ironing. The dry cloth is wound under tension on a perforated cylinder, steam is forced through the cylinder. The moisture and heat cause the wool to become plastic and tension relax and wrinkles are removed. The yarn becomes set in place. Wet decating is preferred to dry decating for better finish. A high degree of lustre can be obtained by the decating process. Napping Figure 11.4 In olden days, the napper tied together several teasels, which is dried vegetable burr of a tree which grows wild in America. The fabric was swept with a plucking motion, across the surface of the fabric to raise the surface from the ground weave. The raised fibres 137

146 Natural and Man-Made Fibres form a nap on the surface that completely changed the appearance of the fabric. Teasels are still used in the machine finishing of fine wool fabrics. For machine processing (gigging), they are mounted on rollers as the barbs break off or wear off the worn out teasels are replaced by new ones. Most napping is done by rollers covered by heavy fabric in which bent wires are embedded. In the double action napping machine the second roll is the counter pile roll and the bent end of the wire point in the direction in which the cloth travels, but the rollers rotate in opposite directions. All these rollers are mounted on a large drum which rotates in the same direction as the cloth. The counter pile roll must travel slower and the pile roller must travel faster. In this process a tucking action occurs. Tucking pushes the raised fibre back into the cloth to give a smooth surface. Figure 11.5 Napping enhances: Warmth - By increasing the dead air space, air gets trapped in here and when the fabric is used as a blanket the body temperature insulates the trapped air. Softness - This property is especially important in baby clothing. Beauty - Napping makes the fabric attractive. Water and stain repellence - Fibre ends on the surface cut down on the rapidity with which the fabric gets wet. 138

147 Finishing Shearing Napped and piled fibres are sheared to control the length of the pile or nap surface. It is a process similar to lawn mowing. Sculptured effects are made by flattening portions of the pile with an engraved roller. And then shearing off the areas that are still erect. Steaming also helps in bringing about a better appearance. Brushing Shearing is followed by brushing to clear off the cut ends. Brushing is combined with steaming to lay the nap in one direction and fix it in that position thus giving the up and down direction of pile and nap fabrics. Chemical Finishes Mercerisation It is the action of caustic soda on a fabric. Cross-linked rayon and high wet modulus rayon can be mercerised. Mercerisation was a revolutionary development discovered by John Mercer. He was a calico printer. He noticed that his cotton filter cloth shrank, became stronger, more lustrous and more absorbent. After filtering the caustic soda used in the filtering process added a lustre and sheen to the filter cloth. The filter cloth also shrank, but became stronger. Little use was made of mercerisation then because it caused yardage loss. In 1897, Lowe discovered that if the fabric were held under tension, it did not shrink but became more lustrous and silk like. Mercerisation is used on silk and cotton for many reasons. It increases the lustre and softness, gives great strength and improves the affinity for dyes and water borne finishes. Mercerised cotton on a label is associated with lustre. Fabric mercerisation is done on a frame which contains mangles for saturating the cloth, a tenter frame for stretching the fabric 139

148 Natural and Man-Made Fibres both crosswise and lengthwise while it is still wet, and boxes for washing neutralizing with dilute acid scouring and rinsing. Mercerisation on cotton fabrics enhances the following properties: Greater absorbency - results from mercerisation because the caustic soda causes a rearrangement of molecules, thus making the hydroxyl groups available to absorb more water and water borne substances. Thus, dyes can enter the fabric readily and they can be fixed inside the fibre. When they are fixed inside then they can be more fast. Mercerised cotton and linen take the resin finishes better. Increased strength might be considered an important plus value for mercerising. The swollen molecules are more parallel to the fibre axis. When stress is applied, the attraction which is in an end to end molecule attraction, is harder to rupture than in the more spiral fibril attachment, and thereby strength is enhanced. Acid finishes The cotton cloth is treated with strong sulphuric acid, to bring about a parchment effect. This is the oldest Swiss finish. Since the acid is strong, the process should be carefully controlled and split second (5 to 6 seconds) timing is necessary to prevent tendering or weakening of the fabric. This process is done to make organdie. After the Haberlein process the fabric is mercerised in order to improve the transparency. The fabric is then dyed or printed with colours that will resist acid damage. Functional Finishes Water proof and water repellent Finishes that can be applied to a fabric to make the fabric repellent are wax emulsions, metallic soaps, and surface active 140

149 Finishing agent. They are applied to fabric which have a very high warp count and are made with fine yarns. These finishes are not permanent and tend to fall out when the fabric is washed. Fire retardant finishes The construction of fabric determines the degree to which oxygen is made available to the fibre. Thick fibres burn slowly. Cotton burns leaving an afterglow. Fire retardant compounds cut off the supply of oxygen to the fabric by forming a coat or by producing a non-combustible gas, or chemically alter the fibre do it forms a non-volatile charred residue rather than a charred residue. Moth and mildew proofing Both moths and carpet beetles attack the fibres. While they can digest only wool they eat on other fabric as well. Means of controlling moth damage: Cold storage Odours that repell. Parachlorobenzene and naphthalene (mothballs) used during storage. Stomach poison. Florides and silicoflorides are used as a finish. Contact poison DDT is very effective but frequent applications are required. 141

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151 Chapter 12: Laundry Value of water in washing S oft water is the most valuable agent used in the laundry work. There is a certain adhesion between fabric and water, hence the water is able to penetrate into the fibre and cause wetting. Pedesis Pedesis or the movement of water particles helps to remove the non-greasy dirt from the fabrics. Thus, the fabric is partially cleaned by steeping and friction. Salt and alkalies in hard water hinder pedesis. The particles are made to aggregate, and the large particles being unable to move in the water will tend to resettle in the fibre. Water is an excellent solvent, therefore much soluble dirt and stain are removed during the steeping process. Cold water is the best solvent. Hot water helps to soften grease, but other cleansing agents are necessary to emulsify and remove greasy matter. The value of using hot water lies in the fact that the solvent power of a liquid increases when its temperature is raised. Rain water Pure water is never found in nature. The purity or otherwise of water depends on the nature of the soil through which it has passed before being collected. Rain water is the most pure form of water, but it contains substances absorbed from the atmosphere one of which is carbon dioxide which is always present, because it gets dissolved in water through the atmosphere. Soft water washes whitest, brightens and saves soap and makes fabrics last longer.

152 Natural and Man-Made Fibres Hard water Most water especially from chalky districts contains calcium and magnesium salts in solutions, usually as sulphate or bicarbonate. These cause hardness. Hardness is of two types: Temporary hardness. Permanent hardness. Temporary hardness Hardness due the presence of calcium or magnesium, bicarbonates is called temporary hardness because it can be removed on heating without the use of chemicals. While the other hardness remains even after boiling. The presence of bicarbonate is due to the action of carbonic acid, which was in the water. When it encountered the insoluble calcium carbonate. The acid dissolves the later substances and holds it in solution. By boiling the carbon dioxide is driven off and the insoluble calcium carbonate is precipitated as chalk and the water is softened. Permanent hardness Compounds of calcium, magnesium, sulphate, chloride and nitrate are known compounds which create permanent hardness in water. The hardness can be removed by distillation or by the use of chemical. Hard water damage It is savage for the clothes to be washed in hard water. It does not lather in washing the lime and magnesium react with soap to make a curd like substance called scum which has no cleaning power. Larger quantities of soap have to be used in order to produce lather. All this makes the fabric harsh and also discoloured them. 144

153 Laundry When water contains hardening substances like calcium and magnesium salts in solution in the water equivalent to 1 gram of CaCO3 in 1 gallon of water the hardness is expressed as (1 of hardness) 1 gallon of water can be softened by 2 grams of soda for each degree of hardness. Each gram of CaCO3 in water will use 10 grams of soap to produce lather. Water containing less than 4 of hardness is known as soft water. Water softening Both temporary and permanent hardness can be removed, the aim should be to soften the water without making it alkaline. Soda removes both kinds of hardness and can be used at home. The most common softening plant is zeolite, which also removes permanent hardness. Soda is inexpensive and easy to use. About 2 grams of soda is needed per degree of hardness. Some other softening agents are caustic soda, ammonia and borax. Borax does not harm fabrics if left in the water. It is useful for water containing more than 20 of hardness. What is in a soap? The word soap comes from either the Gallic (Gaulish) word sapo or a Germanic word saipa. Both sapo and saipa have their origins from the Latin word sebum meaning fat or tallow. Soap is a salt of fatty acid. Soaps are mainly used as surfactants for washing, bathing and cleaning, but they are also used in textile spinning and are important components of lubricants. Soaps for cleansing are obtained by treating vegetable or animal oils and fats with a strong alkaline solution. Fats and oils are composed of triglycerides: three molecules of fatty acids attached to a single molecule of glycerol. The alkaline solution often called lye brings about a chemical reaction known as saponification. In saponification, the fats are first hydrolysed into free fatty acids, which then combine to form crude soap. Glycerol, often called 145

154 Natural and Man-Made Fibres glycerine, is liberated and is either left in or washed out and recovered as a useful by-product. Figure 12.1 Mechanism of cleansing soaps When used for cleaning, soap serves as surfactant in conjunction with water. The cleaning action of this mixture is attributed to the action of micelles, tiny spheres coated on the outside with polar hydrophilic (water-loving) groups, encasing a lipophilic (fat-loving) pocket that can surround the grease particles, causing them to disperse in water. The lipophilic portion is made up of the long hydrocarbon chain from the fatty acid. In other words, whereas normally oil and water do not mix, the addition of soap allows oils to disperse in water and be rinsed away. Synthetic detergents operate by similar mechanisms to soap (refer to Figure 12.2). Structure of a micelle, a cell-like structure formed by the aggregation of soap subunits (such as sodium stearate). The exterior of the micelle is hydrophilic (attracted to water and the interior is lipophilic (attracted to oils). Soap is the chief substance which has been Figure 12.2 used for decades for removing grease and dirt from fibre or fabric. Soap is a well known compound of fatty acids and alkalies. It contains salts such as nitrates and hydroxides of sodium and potassium to make crude soap. Soap makes the 146

155 Laundry penetration of water in the fabric easier. It helps to break down the surface tension or the surface resistance of fabric and thus soap solution will wet the fabric more readily than plain water. The dirt on the fabric consists of grease and dust particles the soap solution breaks up the grease into smaller particles which come off the fabric and float in the solution. With the removal of the grease particles the dust particles also get loosened and as they have a greater affinity towards the soap than the fabric. Thus, the fabric becomes free from both grease and dirt. Most of the non-greasy dirt is removed by steeping in water or the movement of water particles. Soap in water increases the pedesis and thus quickens the removal of non-greasy dirt. A good laundry soap should contain 30% of water, 61 to 64% of combined fatty acids. It should be free of resins. Resins make the fabric yellow with subsequent washing. It should be readily soluble in water and also give a good lather. Sometimes turpentine oil is added to improve the cleansing power of soap. In soap making, both animal and vegetable fat are used. The animal fat are tallow and lard and the vegetable fat are coconut oil and cotton seed oil. There are two types of soaps: soft soaps and hard soaps. Hard soaps Hard soaps are those that do not easily dissolve in water and hence do not give free lather. They make it hard to clean a soiled article. Soft soaps Soft soaps on the other hand dissolve readily in water and give free lather, but because of this very property it gets quickly dissolved in water and gets wasted. Fats which are composed of higher series of fatty acids such as stearin and palmitin in large 147

156 Natural and Man-Made Fibres proportions are termed hard fats and make hard soaps. Tallow and coconut oil produce a hard soap with a firm texture, while castor oil or linseed oil makes soft soap. In addition to the laundry soap, there are other soaps like toilet soap, shaving soap, disinfectant soap and transparent soap. In these, a large variety is brought about by variation in oils, perfume and colour. Colour and perfume are not used in laundry soaps. The process used in soap making are of two kinds: The cold process. The hot process (boiling process). The cold process The cold process is a simple process used in homes to prepare the soap. One of the oils is mixed with caustic soda. The heat given off by the mixture is enough to carry on the process of saponification. Which takes a day or two to be completed. It is necessary to take the correct proportions of the ingredients. This soap has more cleaning power in cold water than in hot water. Recipe Caustic soda: 250 gms Water: 4 cups Coconut oil: 1 Kg Gram powder: 250 gms Method Figure 12.3 an earthen ware pot for 3 to 4 hours. Dissolve caustic soda in water, stand the solution in 148 Mix gram powder (besan) and oil in a bowl. Add caustic soda solution to the mixture of oil and gram flour a

157 Laundry little at a time and continue to stir. Stir in the same direction until a thick consistency is achieved. Pour mixture in moulds and allow the soap to set. Recipe Caustic soda: 250 gms. Water: 5 cups. Coconut oil: 1.5 Kg. Maida: 375 gms. Method Dissolve the soda in water. Warm the oil, mix maida and oil. Add the caustic soda solution to the mixture of oil and stir in one direction. Continue stirring in one direction until thick consistency is achieved. Pour mixture in moulds and allow to set. The hot process (boiling process) This process is the commercial method of soap making. Fats oils and the alkali are purified. Fats are melted in a large pan. A weak solution of caustic soda is added gradually and the mixture is boiled by steam passed directly in the pan at 80 to 100 C, a little below boiling point, until saponification is completed, which before modern scientific equipment was developed, the soap maker would determine by taste (the sharp hydroxide taste disappears after it is saponified) or by seeing the texture. Tasting soap for readiness is not advisable because sodium and potassium hydroxides are highly caustic. Some of the fat is saponified and the 149

158 Natural and Man-Made Fibres soap forms an emulsion of the whole mixture. More caustic soda is added at intervals and the process of boiling is continued for two to three days. The contents of the soap pan are soap, glycerine, excess of caustic soda and some impurities, brine solution is added which separates the soap out and this forms a layer on the top. The liquid under this layer consists of glycerine and impurities and is known as spent lye. CH3(CH2)nCOOH + NaOH CH3(CH2)nCOONa + H2O Figure Process diagram of soap. Spent lye is taken out and glycerine is distilled and stored. The soap layer is mixed with water and boiled and made into a paste. This may contain some unsaponified fat and therefore some more caustic soda is added till saponificaton is complete. Brine solution is added as before and spent lye is removed. The soap is then boiled with steam and left to stand until four layers are formed. The top layer is just a forth, the second layer is the genuine soap, which is run off by a pipe, the third layer is an 150

159 Laundry impure dark coloured soap and the fourth layer is some alkaline liquid. The advantage of the full boiled hot process is that the exact amount of hydroxide required need not be known with great accuracy, after saponification has taken place the neat soap is precipitated from solution by adding common salt, and the excess liquid is drained off. This excess carries away with it much of the impurities and colder compounds in the fat. All the glycerine is also removed to leave a whiter soap. The soap is then passed into crutching pans when colour or perfume are added. Then the soap is moulded and cut or made into flakes or powders. What is a detergent? 1. Active ingredients to remove soil and produce foam or suds, by themselves, for heavy-duty wash, a second major component are necessary - a builder. 2. Builders are of 2 types: inorganic and organic. The inorganic builders are primarily phosphates, but they do not foam or sud, they do increase detergency (by reducing the surface tension of the water). Organic builders - These builders also act as water softeners. 3. Anti deposition agent which is needed to keep soil suspended once it has been removed. 4. Sodium silicate is used to protect pots and pans and aluminium washer parts such as agitators, fans, tubs, etc from pitting or attack by inorganic builders. 5. Brightener or optical bleach is added for white effect on the fabric. 151

160 Natural and Man-Made Fibres Difference Between Detergent and Soap Detergents (1) Detergents are made chemically in factories. (2) Greater cleansing efficiency is achieved with modern detergents. (3) They do not combine with the calcium, magnesium and other salts present in water. (4) Detergents remove the soapy deposits. (5) Greater efficiency against body acids. They wash effectively even in acid medium. (6) Wash well even in cold water and hard water. (7) Detergents have high penetrating power and effectively remove soap. (8) Rapid removal of grease is a very desirable characteristic. Do not allow grease to settle again on the fabric keep it dispersed to water. (9) Greater economy, less detergent is required. Soaps (1) Soaps are made from natural fats, oil and waxes. (2) Do not clean as much as detergents. (3) Soaps combine with calcium and magnesium and do not lather as much as detergents. (4) Soapy deposits are left by soaps. (5) Soaps have the capacity to carry water droplet. (6) Soaps do not work well in cold and hard water. (7) Do not penetrate as efficiently. (8) Soaps when used may leave soap marks on the fabric and soil may cling to the fabric (leave no scum). (9) Soaps after being used ones are wasted as are keep dissolving. 152

161 Laundry Optical bleaches Optical bleaches are used for off-white and white fabrics. These compounds do not bleach the fabric, but change the reflection of the light rays. They reflect blue light more for this effect fluorescent colourless dyes are used. These dyes change the invisible ultraviolet light into visible light. So the colour of the fabric becomes dependent upon the light in which it is seen in sunlight, these fabrics look dazzling white. These fluorescent whiteners are often incorporated in detergents as whiter than new. Bleaching Bleaching cleans and whitens grey goods. In home laundry, bleaches are used to whiten clothes that are stained and become yellow after repeated washing. Bleaching is a chemical reaction, in which two types of reactions take place: (1) Oxidation. (2) Reduction. (1) Oxidation In this to remove the colour sodium or chlorine compounds are brought into use H2O2, hypochlorite, sodium hypochlorite, sodium chlorate, potassium chromate (K2CrO4), potassium permanganate (KMNO4), sodium chlorite are the various compounds used for bleaching. (2) Reduction Chlorine bleaches are used for cellulose fibre. The bleaching is done by hypochlorous acid liberated during the bleaching process, tender cellulosic fibre. Chlorine bleaches are bactericidal agents. 153

162 Natural and Man-Made Fibres Reducing bleaches Used for bleaching protein fibre like wool, but the reaction is temporary. The colour comes back on exposure to oxygen. The compounds brought into the use are zinc dust, stannous chloride SnCl2.2H2O, sodium hyposulphite (Na2S2O4). Laundry blues The tint of blue in laundry is used: (1) In complete washing on which bleaching would cause no improvement. (2) The deposition of line or iron soaps on the fabric. (3) The reappearance of natural colouring. Contrary to the general belief bleaching does not whiten clothes it only neutralizes the yellow tinge. Blue is the complementary colour to white. Types of blues (1) Insoluble in water: e.g. Ultramarine blue. (2) Soluble in water: Several coal tar dyes, methyl violet, and methylene blue, Prussian blue. Ultramarine blue: It is manufactured from soda ash, sodium sulphate, charcoal sulphur and clay. All these are heated and then ground. It makes a fine powder and thus becomes a suitable blue for laundry. It is a safe blue to use and is not harmful to fabrics. It is not affected by alkalies, it is sometimes used together with soap so that the blue is boiled in bluing with ultramarine blue. It may cause trouble by large particles forming specks on the fibre. The care required with ultramarine has caused the abandonment of its use in many laundries in favour of the more simple application of soluble blues and fluorescent washing powders. 154

163 Laundry Prussian blue: This is ferric ferrocynide. It was discovered in the eighteenth century. It is a mixture of iron sulphate with potassium ferrocynide. This is also insoluble in water. Its use is undesirable as it is a compound of iron and is decomposed by alkaline substances. Indigo: This is directly prepared from the leaves of a certain plant, and it is not manufactured synthetically. It is not very much used in laundry. It has a dull blue colour. Aniline blue: This is made from coal tar dyes. Its colour may vary from blue to purple. It is of two kinds. One gives best results in acid medium and the other in an alkaline medium. This is readily soluble and is therefore the best to use in laundry. Indigo and ultramarine are not completely soluble in water and remain in suspended particles. Suspended blues will not give an even colour to the fabrics apart from leaving patchy discolourations. These are actually dyes and are marketed in great variety by manufacturers, they are easy to prepare, control and apply. These are aniline dyes. Purplish blue being the most common shade, as it gives a whitish appearance. 155

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178 Natural and Man-Made Fibres The stain removal chart has been adapted from Household Textiles and Laundry Work by Durga Deulkar. 170