SPECIALTY CARBONS FOR POLYMER COMPOUNDS

Transcription

1 Polymers SPECIALTY CARBONS FOR POLYMER COMPOUNDS ENSACO TIMCAL Carbon Black TIMREX TIMCAL Graphite TIMREX TIMCAL Coke TIMREX TIMCAL Dispersion imerys-graphite-and-carbon.com

2 Imerys Graphite & Carbon WHO ARE WE? IMERYS Graphite & Carbon has a strong tradition and history in carbon manufacturing. Its first manufacturing operation was founded in Today, IMERYS Graphite & Carbon facilities produce and market a large variety of synthetic and natural graphite powders, conductive carbon blacks and water-based dispersions of consistent high quality. Adhering to a philosophy of Total Quality Management and continuous process improvement, all Imerys Graphite & Carbon manufacturing plants comply with ISO 9001:2008. IMERYS Graphite & Carbon is committed to produce highly specialized graphite and carbon materials for today s and tomorrow s customers needs. IMERYS Graphite & Carbon belongs to IMERYS, the world leader in mineral-based specialties for industry. WHERE ARE WE LOCATED? With headquarters located in Switzerland, IMERYS Graphite & Carbon has an international presence with production facilities and commercial offices located in key markets around the globe. The Group s industrial and commercial activities are managed by an experienced multinational team of more than 430 employees from many countries on three continents. For the updated list of commercial offices and distributors please visit Lac-des-Îles, Canada Mining, purification and sieving of natural graphite flakes HQ Bodio, Switzerland Graphitization and processing of synthetic graphite, manufacturing of water-based dispersions, processing of natural graphite and coke, and manufacturing and processing of silicon carbide Changzhou, China Manufacturing of descaling agents and processing of natural graphite Terrebonne, Canada Exfoliation of natural graphite, processing of natural and synthetic graphite Willebroek, Belgium Manufacturing and processing of conductive carbon black Fuji, Japan Manufacturing of water-based dispersions WHAT IS OUR MISSION? To promote our economic, social and cultural advancement with enthusiasm, efficiency and dynamism by offering value, reliability and quality to ensure the lasting success of our customers. WHAT IS OUR VISION? To be the worldwide leader and to be recognized as the reference for innovative capability in the field of carbon powder-based solutions. 2

3 Contents ENSACO conductive carbon black TIMREX graphite and coke Specialty carbons for polymer compounds THE PRODUCTS Introduction to ENSACO conductive carbon black p. 4 Introduction to TIMREX graphite and coke p. 5 ENSACO conductive carbon black for polymer compounds p. 6 TIMREX graphite and coke for polymer compounds p. 8 TYPICAL APPLICATIONS FOR ENSACO CONDUCTIVE CARBON BLACK Electrically conductive plastics p. 10 Rubber p. 14 Power cables and accessories p. 17 TYPICAL APPLICATIONS FOR TIMREX GRAPHITE AND COKE Self lubricating polymers p. 18 Filled PTFE p. 20 Thermally conductive polymers p. 22 3

4 Introduction to ENSACO conductive carbon black THE PRODUCTS Conductive carbon blacks are carbon blacks with high to very high stucture (or void volume) allowing the retention of a carbon network at low to very low filler content. The void volume can originate from the interstices between the carbon black particles, due to their complex arrangement, and from the porosity. HOW ENSACO CONDUCTIVE CARBON BLACKS ARE PRODUCED The Imerys Graphite & Carbon carbon black process has been developed around 1980 and is commercially exploited since The plant uses most modern technology. The process is based on partial oil oxidation of carbochemical and petrochemical origin. The major difference with other partial combustion carbon black technologies lies in the aerodynamic and thermodynamic conditions: low velocity; no quench; no additives. This leads to a material with no or nearly no sieve residue on the 325 mesh sieve and allows the highest possible purity. The granulation process has been developed to achieve an homogeneously consistent product maintaining an outstanding dispersibility. It is in fact a free-flowing soft flake characterised by a homogeneous and very low crushing strength that guarantees the absence of bigger and harder agglomerates. The process enables the production of easily dispersible low surface area conductive carbon blacks as well as very high surface area conductive carbon blacks. The unique combination of high structure and low surface area also contributes to give outstanding dispersibility and smooth surface finish. The low surface area materials show a chain-like structure comparable to acetylene black. The very high surface area materials belong to the extra conductive (EC) family. Although ENSACO carbon blacks are slightly more graphitic than furnace blacks, they are quite close to the latter ones as far as reinforcement is concerned. ENSACO carbon blacks combine to a certain extent both the properties of furnace and acetylene black, reaching the optimal compromise. 100 nm TEM picture of ENSACO 250G carbon black showing the high level of aggregation. By courtesy of University of Louvain (Louvain-La-Neuve) STM picture of the surface of ENSACO 250G carbon black 5x5 nm. By courtesy Prof. Donnet - Mulhouse 100 nm SEM picture of ENSACO 250G carbon black illustrating the high void volume. By courtesy of University of Louvain (Louvain-La-Neuve) 4

5 Introduction to TIMREX graphite and coke Graphite finds wide application thanks to its favourable combination of properties such as: low friction, chemical inertness and absence of inherent abrasiveness; high thermal conductivity, thermal stability and electrical conductivity; film forming ability on metal surfaces; relatively inoffensive nature of both powders and products of combustion. THE PRODUCTS These properties are a consequence of the lamellar graphite structure and the anisotropic nature of chemical bonding between carbon atoms. In graphite, three sp 2 hybrid orbitals (each containing one electron) are formed from the 2s and two of the 2p orbitals of each carbon atom and participate in covalent bonding with three surrounding carbon atoms in the graphite planes. The fourth electron is located in the remaining 2p orbital, which projects above and below the graphite plane, to form part of a polyaromatic π-system. Delocalisation of electrons in π-electron system is the reason of graphite s high stability and electrical conductivity. Interlamellar bonding was once thought to be weak and mainly the result of Van der Waals forces, however, it now appears that interlamellar bonding is reinforced by π-electron interactions. Graphite is therefore not intrinsically a solid lubricant and requires the presence of adsorbed vapours to maintain low friction and wear. HOW TIMREX GRAPHITE AND COKE POWDERS ARE PRODUCED TIMREX PRIMARY SYNTHETIC GRAPHITE TIMREX primary synthetic graphite is produced in a unique highly controlled graphitization process which assures narrow specifications and unequalled consistent quality thanks to: monitoring of all production and processing stages, strict final inspection, and clearly defined development processes. TIMREX primary synthetic graphite shows unique properties thanks to the combination of a consistent purity, perfect crystalline structure and well defined texture. TIMREX NATURAL FLAKE GRAPHITE TIMREX natural flake graphite is produced in a wide range of products distinguished by particle size distribution, chemistry and carbon content. Imerys Graphite & Carbon mines the graphite from its own source in Lac-des-Îles, Quebec, Canada. Further processing can be done either in Lac-des-Îles or in our processing plant in Terrebonne, Quebec, Canada. All TIMREX naturals are thoroughly controlled in our laboratories to ensure quality, consistency and total customer satisfaction. TIMREX COKE TIMREX petroleum coke is calcined at appropriate temperature with low ash and sulphur content, well defined texture and consistent particle size distribution. Lc c c/2 SEM picture of TIMREX Graphite showing the perfect crystalline structure. c/2 = Interlayer distance Lc = Crystallite height 5

6 ENSACO conductive carbon black for polymer compounds THE PRODUCTS TYPICAL VALUES PROPERTY TEST METHOD UNIT ENSACO 150G ENSACO 210G ENSACO 250G ENSACO 260G ENSACO 350G Form Granules (*) Granules Granules (*) Granules Granules BET nitrogen surface area ASTM D3037 OAN absorption ASTM D2414 (1) COAN crushed OAN ASTM D2414 (1) Pour density ASTM D1513 Moisture (as packed) ASTM D1509 Sieve residue 325 mesh (45 μm) ASTM D1514 Ash content ASTM D1506 Volatile content TIMCAL Method 02 (2) Sulphur content ASTM D1619 Toluene extract ASTM D4527 ph ASTM D1512 Volume resistivity TIMCAL Method 11 (3) (4) m 2 /g ml/100 g ml/100 g kg/m % max ppm % % 0.2 max 0.2 max 0.2 max 0.2 max 0.3 max % 0.5 max 0.5 max % 0.1 max 0.1 max 0.1 max 0.1 max 0.1 max Ohm.cm 2000 max (3) 500 max (3) 10 max (3) 5 max (3) 20 max (4) (1) Spring: 0.9 lbs/inch; 10 g of carbon black (2) Weight loss during heating between 105 and 950 C (3) 25% carbon black in HDPE Finathene (4) 15% carbon black in HDPE Finathene (*) ENSACO 150 and ENSACO 250 are also available in powder form. 6

7 TYPICAL EFFECTS ON POLYMER COMPOUNDS THE PRODUCTS PROPERTY ENSACO 150G ENSACO 210G ENSACO 250G ENSACO 260G ENSACO 350G Form Granules (*) Granules Granules (*) Granules Granules BET nitrogen surface area (m 2 /g) OAN oil absorption (ml/100 g) Conductivity Dispersibility Purity Water absorption very low very low very low very low high Surface smoothness Electrical/mechanical properties balance Resistance to shear Comments to application domains MRG (mechanical rubber goods) Easy strippable insulation shields All polymers excellent very good good quite good difficult (*) ENSACO 150 and ENSACO 250 are also available in powder form. 7

8 TIMREX graphite and coke for polymer compounds THE PRODUCTS TYPICAL VALUES PARTICLE SIZE RANGE (µm) GRADE ASH (%) SCOTT DENSITY (g/cm 3 ) SURFACE AREA BET (m 2 /g) Synthetic graphite KS graphite KS6 KS15 KS5-25 KS44 KS5-44 KS SFG graphite SFG6 SFG44 SFG * T graphite T15 T44 T Natural graphite PP flake graphite PP10 PP44 <5 < LSG flake graphite LSG10 LSG44 <1 < Large flake graphite Cumulative size min. 80% <150 mesh (105 µm) min. 80% >150 mesh (105 µm) M150 80X150 <6 <6 0.4* 0.6* Coke PC coke Oversize control min. 98% <45 µm (air jet sieving) max. 0,1% >106 µm (air jet sieving) PC40-OC * 10.0 Water-based dispersion GRADE ASH (%) DENSITY (g/cm 3 ) 20 C PARTICLE SIZE DISTRIBU- TION d90 (µm) SOLID CONTENT (%) LB dispersion LB Special grade GRADE ASH (%) SCOTT DENSITY (g/cm 3 ) FORM C-THERM C-THERM 001 < * soft granules D90 (µm) C-THERM 011 < * soft granules C-THERM 002 < * powder 81 C-THERM 012 < * powder * bulk density 8

9 MEET CONDUCTIVITY TARGETS WITH DEDICATED IMERYS GRAPHITE & CARBON ADDITIVES 9

10 Electrically conductive plastics TYPICAL APPLICATIONS FOR ENSACO CONDUCTIVE CARBON BLACK THE SELECTION OF A CONDUCTIVE CARBON BLACK THE PREPARATION OF A CONDUCTIVE COMPOUND ENSACO conductive carbon blacks find their applications in an unlimited number of plastics. The combination of the polymer type and grade and the carbon black grade are determining the overall electrical and mechanical performance. The main parameter influencing the final conductivity of a finished part in a given polymer is the type and level of carbon black used. The higher the structure of the carbon black, the lower the level of carbon black needed to achieve the required conductivity. Nevertheless, in a minor way, other parameters like the additives in presence, the compounding or processing conditions may also influence the final conductivity of parts. Low surface area conductive carbon blacks show a particular advantage on dispersion and processing. Percolation curves correlating the volume resistivity and the carbon black percentage are a useful comparative tool to predict the conductivity in place and to select the more appropriate system. These curves are valid for a given formulation and sample preparation technique. The selection of the conductive carbon black will also influence: the compounding behaviour (dispersibility, resistance to shear, mixing cycle, melt flow index, extrusion throughput); the surface appearance of the finished material (number of surface defects); the mechanical properties(polymer property retention, reinforcement); the overall price performance ratio. Suitable mixing equipments for the preparation of black conductive compounds include internal mixers, twin screw extruders, single screw kneader machines and LCM. The feeding of low bulk density, soft flake-type carbon blacks into extruders requires the use of twin screw feeders and separate introduction on an already molten polymer (split feeding technology). SOME TYPICAL FINAL PLASTICS APPLICATIONS handling of electronic components: carrier boxes, carrier trays, carrier tapes, etc.; films: antistatic and conductive films, packaging films, garbage bags, etc.; automotive industry: fuel injection systems, anticorrosion systems, fuel tank inlet, electrostatically paintable parts, etc.; transport: mobile phone parts, wheels, containers, bins, pallets, etc.; computer: antistatic articles for computer & accessories, CD player, etc.; health: medical applications, cleanroom equipments, articles for antistatic workplaces, etc.; antistatic flooring; heating element; sensors; PTC switches; UV protection and pigmentation. In the following pages there are some of the results of experimental work carried out on ENSACO conductive carbon blacks in different polymer compounds. The data shown here are given as orientation and are valid for the particular formulations and sample preparation technique mentioned. (Results in other polymers, full studies and publications are available upon request). 10

11 ENSACO CONDUCTIVE CARBON BLACKS IN HDPE Influence of the carbon black type on the resistivity The higher the structure of the carbon black, the lower the percolation threshold. Various carbon blacks in HDPE 10 9 Volume resistivity (Ohm.cm) Carbon black concentration (%) At a concentration very near to the percolation level, when overmixed, ENSACO 260G offers a higher consistency in resistivity resulting from its higher shear stability in extreme working conditions. Resistivity vs mixing time - 18% carbon black ENSACO 250G ENSACO 260G ENSACO 350G ing: laboratory Brabender internal mixer. Processing: compression moulding. TYPICAL APPLICATIONS FOR ENSACO CONDUCTIVE CARBON BLACK Volume resistivity (Ohm.cm) Brabender mixing time (min) ENSACO 250G ENSACO 260G At a concentration far above the percolation level, both blacks are very stable in resistivity when overmixed. ENSACO 260G shows a consistent lower resistivity. Resistivity vs mixing time - 25% carbon black Volume resistivity (Ohm.cm) Brabender mixing time (min) ENSACO 250G ENSACO 260G 11

12 Electrically conductive plastics TYPICAL APPLICATIONS FOR ENSACO CONDUCTIVE CARBON BLACK ENSACO CONDUCTIVE CARBON BLACKS IN LDPE ENSACO CONDUCTIVE CARBON BLACKS IN PP Influence of the carbon black type and of the MFI of the starting polymer on the resistivity The higher the structure of the carbon black, the lower the percolation threshold. At equal structure, the carbon black of lower surface area gets an advantage on resistivity that may be coming from the easier dispersion resulting in smoother compounding. The higher the meltflow index of the starting polymer, the lower the percolation threshold. Various carbon black in LDPE MFI 0.3 and 36 (g/10 min) Volume resistivity (Ohm.cm) Carbon black concentration (%) ENSACO 250G LD 0.3 ENSACO 250G LD 36 N472 LD 0.3 N472 LD 36 P-type LD 0.3 P-type LD 36 ing: laboratory Brabender internal mixer. Processing: compression moulding. Influence of the carbon black type on the resistivity. Relation between resistivity and melt flow index At same structure level, the carbon black with the lowest surface area has the smallest impact on fluidity reduction. PPH MI54 (230 C/5 kg) with various conductive carbon blacks Volume resistivity (Ohm.cm) ENSACO 250G high structure low surface area N472 high structure high surface area ing and processing: twin screw extruder Haake PTW16 and realization of tapes. MFI (230 C/5 kg) (g/10 min) Influence of carbon black loading and processing on the resistivity Injection moulding generates more shear than compression moulding. The closest to the percolation, the more visible is that effect. A concentration safety margin can overcome this phenomenon. Volume resistivity (Ohm.cm) strands pellets + pressed plaques 4.6E pellets + injection moulding 13.5% ENSACO 250G 15% ENSACO 250G ing: ZSK25 twin screw extruder. Processing: injection moulding. 12

13 ENSACO CONDUCTIVE CARBON BLACKS IN PC Influence of the carbon black type on the resistivity Volume resistivity in function of carbon black loading Volume resistivity (log (Ohm.cm)) Izod (kj/m 2 ) Carbon black concentration (%) Volume resistivity (log (Ohm.cm)) ENSACO 250G ENSACO 350G ing: ZSK57 twin screw extruder. Processing: injection moulding. Influence of the carbon black type on mechanical and rheological performances Although the concentration for percolation is double the level with ENSACO 250G, most mechanical properties are still better. Izod impact strength, notched, in function of volume resistivity ENSACO 250G ENSACO 350G ing: ZSK57 twin screw extruder. Processing: injection moulding. TYPICAL APPLICATIONS FOR ENSACO CONDUCTIVE CARBON BLACK Tensile strength for both carbon blacks is almost at the same level. Tensile strength in function of volume resistivity Tensile strength (MPa) Volume resistivity (log (Ohm.cm)) ENSACO 250G ENSACO 350G 13

14 Rubber TYPICAL APPLICATIONS FOR ENSACO CONDUCTIVE CARBON BLACK Carbon black is one of the main ingredients of any rubber compound. Conductive carbon blacks are before all carbon blacks, to be mixed and handled as any other reinforcing or semireinforcing carbon black. They are high structure materials bulky by nature. Although the common carbon blacks are conductive by nature and impart also conductivity to the compounds when used in sufficiently high loading, conductive carbon blacks have the advantage to reach conductivities at lower loading and are often used to give the final boost to a compound already filled with other carbon blacks. As carbon black structure is the parameter determining the conductivity, structure being an additive property, the combinations of conductive and normal black can be predicted. Specifications of rubber compounds being usually quite complex and conductivity being only one of the numerous physical requirements, the use of carbon black blends is very often the only solution. In some specific cases, especially in special polymers, it occurs that the conductive carbon black is used by its own in order to maintain mechanical properties and processing at a good level. ENSACO carbon blacks are, quite close to furnace blacks as far as the reinforcing activity is concerned. Especially the low surface area carbon blacks, grades 150, 250 and 260, are, due to their very easy dispersion, quite performing in most rubber compounds. ENSACO 350 is also used in some compounds where small additions are required. A few conductive applications: belt cover compounds; flooring; conveyer belts; hoses for fuel, for conveying of powders, etc.; cylinder coating; shoe soles; seals. ENSACO 150 and 250 are also used in non conducting applications where the compounder can take profit of the low surface area and high structure of those blacks: low hysteresis with relatively high hardness; good thermal aging; very good tear strength; very good dispersion, very good mechanical performance at thin layer. A few non-conductive applications: antivibration systems; textile coating; membranes; articles exposed to chipping and chunking. In the following pages there are some of the results of experimental work carried out on ENSACO conductive carbon blacks in different rubber compounds. The data shown here are given as orientation and are valid for the particular formulations and sample preparation technique mentioned. Results in other polymers, full studies and publications are available upon request. 14

15 NBR CONDUCTIVE HOSE COMPOUND A ENSACO 250 B N-472 NBR NT ENSACO N N ZnO 4 4 Stearic acid DOP Sulphur Methyl thuads 2 2 Amax 2 2 By courtesy of Bayer A ENSACO 250 B N-472 t90% (min) Mooney ML (1+4) at 100 C Vulcanizate data unaged at RT Shore A Hardness Stress-strain Elongation at break (%) Tensile Strength (MPa) Modulus 100% (MPa) Modulus 300% (MPa) Modulus 500% (MPa) Resistivity (Ohm.cm) Tear Strength (N/mm) TYPICAL APPLICATIONS FOR ENSACO CONDUCTIVE CARBON BLACK CONDUCTIVE CR CONVEYOR BELT COVER COMPOUND A B A B ENSACO 250 N-472 ENSACO 250 N-472 Bayprene 610 (CR) Buna CB MgO powder 4 4 N ENSACO Vulkanox DDA Vulkanox Ingralen ZnO powder 5 5 Rhenogran ETU Stearic acid By courtesy of Bayer Dispersion rating DIK t90% (min) Mooney ML(1+4) at 100 C Vulcanizate data unaged at RT Shore A hardness Stress-strain Elongation at break (%) Tensile strength (MPa) Modulus 50% (MPa) Modulus 100% (MPa) Modulus 300% (MPa) Modulus 500% (MPa) Compression set 24h at 70 C (%) Resistivity (Ohm.cm)

16 TYPICAL APPLICATIONS FOR ENSACO CONDUCTIVE CARBON BLACK FKM CONDUCTIVE COMPOUNDS Mooney viscosity ML (1+10 ), 100 C VITON A-32J - Fluoroelastomer MgO Ca(OH) MT black (N990) ENSACO 250G N-472 SCF VPA Total phr MT black % ENSACO 250G % SCF N-472 % Experimental data provided by DuPont Dow Elastomers, Japan (*) 9 t 90% (min) Log resistivity (Ohm.cm) Compression set (%) Shore A (*) Rejected because uncurable. Vulcanizate properties at 177 C for 10 min. 16

17 Power cables and accessories TYPICAL EVA/ NBR STRIPPABLE COMPOUNDS Conductive carbon black is used in semicon compounds for conductor and insulator shields. The requirements for those compounds are besides processing, a sufficient electrical conductivity, a smooth or even supersmooth surface finish, and high purity. For strippable or easy strippable compounds these requirements are added to a specific adhesion strength between the insulating layer and the insulator shield. These strippable or easy strippable layers have to peeled of by hand or using a specific peeling device. Typical polymer compositions are polyolefins or copolymers; for strippable compounds quite often blends of EVA and NBR are used. N-472 ENSACO 210 ENSACO 250 Levaprene Perbunan NT Rhenogran P N ENSACO ENSACO N Antilux Zn stearate Rhenovin DDA Rhenofit TAC/CS Percadox BC TYPICAL APPLICATIONS FOR ENSACO CONDUCTIVE CARBON BLACK TYPICAL EEA/EBA SEMICON COMPOUNDS Viscosity ML (4+1) Rheometer@180 t90% Mechanical properties Non aged (diff. aged) Tensile strength (MPa) 16.5 (-19) 16.9 (-15) 16.9 (-15) Elongation at break (%) 215 (-58) 180 (-50) 170 (-53) Modulus 100% (MPa) Shore A 87 (+7) 90 (+4) 89 (+7) Peel strength hot TYPICAL air 100 C (N) EEA/EBA 7SEMICON COMPOUNDS after 3 days (N) after 21 days (N) Volume resistivity (Ohm.cm) EEA EEA 100 EBA EBA 100 ENSACO Peroxide Mixing cond. L/D15; Feed BC; Truput 30 RT C Carbon black dispersion: <3µm Die pressure (bar) MFI (g/10 min) Specific net mixing energy (kwh/kg) Protrusion (N /m 2 )

18 Self lubricating polymers TYPICAL APPLICATIONS FOR TIMREX GRAPHITE AND COKE The choice of a polymer-based self lubricating solid for a particular application depends mainly upon the operating conditions of: temperature, chemical environment and the maximum values of pressure (p) and sliding speed (v). For each polymer or composite material, a pv limit is quoted, which corresponds to the pressure times the sliding speed at which the material fails, either due to unacceptable deformation, or to the high frictional energy dissipated causes surface melting, softening and excessive wear. The pv limit of a polymeric material may be increased by increasing its mechanical strength (resistance to deformation), thermal conductivity (reduction in surface temperatures) and by decreasing friction (reduces frictional heating). In practice, thermoplastics (with the exception of PTFE) are mainly used as pure solids, since their wear resistance and frictional coefficient, are satisfactory for most applications. Solid lubricant fillers or fibre reinforcement (glass fibres, carbon fibres, textiles) are only employed under the more extreme conditions of load and speed. The major polymers employed as self lubricating solids/composites, are illustrated below. Graphite powder is widely used in polymer composites, either alone or in combination with reinforcing fibres, PTFE or various inorganic fillers, e.g. mica, talc. Applications include gears, dry sliding bearings, seals, automotive and micro-mechanical parts. The properties of graphite which favour its use in polymer composites are: low friction lamellar solid (reduces friction); tendency to form a transfer film on the countersurface (assists in wear reduction, particularly when graphite is applied as water based dispersion i.e. TIMREX LB1300); high thermal conductivity (decreases temperature rise due to frictional heating); electrical conductivity (prevent build-up of static charge which may be a problem in some cases); chemically inert (used in conjunction with PTFE in corrosive environments); high thermal stability (favours use in high temperature applications, e.g. polyimide graphite composites may be used up to 350 C). Incorporation of graphite powder into a thermoplastic polymer will generally result in a reduction in the friction coefficient (with the exception of PTFE) but rarely improves the wear resistance. This behaviour is illustrated in the two graphs, which show the mean friction coefficient and specific wear rate for a stainless steel ball (ø = 5 mm) rubbing on discs of graphite filled polystyrene and polyamide at constant load (32.5 N) and speed (0.03 m/s). The specific wear rates of the graphite-polymer composites were calculated from the diameters of the wear tracks and the contact geometry. In the case of polystyrene, addition of 30 50% of a high purity macrocrystalline synthetic graphite (TIMREX T75), reduced both friction and wear rate. With polyamide however, addition of a graphite similar to TIMREX T75 reduced the friction coefficient, but caused a slight increase in the wear rate, with the finer particle size powder (TIMREX KS6) giving the better result. In the case of low density polyethylene and polypropylene, graphite incorporation causes both an increase in friction and wear. 18

19 The results described above are thought to be related to the strength of adhesion at the polymer-graphite interface, which depends upon the wettability of the powder by the molten polymer, powder surface area to volume ratio, surface chemistry, etc. In simple terms, polystyrene shows a strong affinity for the graphite surface, while polyolefins show a weak affinity. Interfacial adhesion increases with increasing powder surface area to volume ratio, or decreasing particle size. For this reason relatively fine graphite powders (95%<15 microns) are recommended for thermoplastics. The strength of thermosetting polymers is much less sensitive to filler-polymer interactions, therefore coarser graphite powders may be used (typically 95%<75 microns). For thermoplastics, the viscosity of the polymer-graphite melt during extrusion/moulding will also depend on the graphite particle size, which should be appropriate. Excessive graphite surface area may also lead to void formation in the finished composite, due to desorption of physisorbed vapours in the hot melt. High graphite purity is generally desirable in order to minimize wear, although this parameter is unlikely to be important in the presence of abrasive fillers (glass fibre, carbon fibre). Ball/disc friction & wear data: polystyrene/graphite filler Specific wear (m 3 /Nm)x Wear Friction pure polystyrene 30% TIMREX T75 50% TIMREX T Friction coefficient Influence of graphite addition on the specific wear rate and friction of polystyrene TYPICAL APPLICATIONS FOR TIMREX GRAPHITE AND COKE Ball/disc friction & wear data: polyamide 6/graphite filler Specific wear (m 3 /Nm)x Wear Friction Friction coefficient 5 0 pure polyamide 30% TIMREX KS6 30% TIMREX KS Influence of graphite addition on the specific wear rate and friction of polyamide 6 The above mentioned results are the confirmation that TIMREX graphite powder is an excellent additive to produce self-lubricated polymers. The addition of TIMREX graphite powder to the unfilled polymers allow for a reduction of the friction coefficient and in most of the cases to a reduction of the wear rate. These results are achieved by a synergic combinations of all the good properties of TIMREX graphite powder that among the others are: the high degree of crystallinity, the extremely high purity, the optimal texture and the perfect particle size distribution. All of them linked by a common factor: the consistency! 19

20 Filled PTFE TYPICAL APPLICATIONS FOR TIMREX GRAPHITE AND COKE Polytetrafluoroethylene (PTFE) exhibits a very low coefficient of friction and retains useful mechanical properties at temperatures from -260 to +260 C for continuous use. The crystalline melting point is 327 C, much higher than that of most other semicrystalline polymers. Furthermore, PTFE is nearly inert chemically and does not adsorb water, leading to excellent dimensional stability. On the one hand, these characteristics of PTFE are very useful in the matrix polymer of polymer-based composites which are used in sliding applications. On the other hand, PTFE is subjected to marked cold flow under stress (deformation and creep) and reveals the highest wear among the semicrystalline polymers. However, these disadvantages are very much improved by incorporating suitable fillers, allowing the use of PTFE in fields otherwise precluded to this polymer. The treated PTFE is generally known as filled-ptfe. There are many kinds of filled- PTFE composite because various fillers are incorporated into PTFE and one or more materials can be used simultaneously. Usually, these fillers are in form of powders or fibers intimately mixed with the PTFE. The addition of fillers to the PTFE improves or modifies its properties depending upon the nature and quantity of filler: remarkable increase in wear resistance; decrease of deformation under load and of creep; reduction of thermal expansion; some types of filler increase the thermal and electric conductivity. Filled PTFE is often not as strong and resilient as virgin PTFE. Sometimes, the filler limits the resistance to chemical agents and modify the electrical properties. TIMREX GRAPHITE AND COKE FILLERS IN FILLED-PTFE TIMREX PC40-OC coke TIMREX PC40-OC coke is calcined at high temperatures offering low sulphur concentration, low content of oversize particles, high apparent density and high chemical stability against most chemical substances. TIMREX PC40-OC coke is added to the virgin PTFE in a percentage by weight between 10 and 35% along with small percentage of graphite. s made of PTFE and TIMREX PC40-OC coke have excellent wear resistance and deformation strength and compared to the virgin PTFE, they have practically unchanged chemical resistance and friction behaviour. Typical final materials that can be produced with coke filled PTFE are: engineering design components, slide bearings, valve housing and valve seats for chemical applications, piston sealing and guiding elements for dry-running compressors. TIMREX KS44 synthetic graphite TIMREX KS 44 is a primary synthetic graphite obtained by the full graphitisation of amorphous carbon materials through the well known Acheson process. The process parameters in the Acheson furnace such as temperatures and residential times are all optimised in order to achieve the perfect degree of crystallinity and the lowest level of impurities whereas others minor adjustments are made during the material sizing and conditioning. The percentage of TIMREX KS44 used in the filled PTFE vary between 5 and 15%. TIMREX KS44 can be used alone or in combination with glass or coke. TIMREX KS44 lowers the coefficient of friction and is, therefore, often added to other types of filled PTFE for improving this property (and also to improve the lifetime of the cutting tools during for instance the production of gaskets and seals). It improves the deformation under load, strength and, to a minor degree the wear. Like coke, it serves well in corrosive environments. PTFE filled with TIMREX KS44 are often used in steering and shock-absorber gasket, bearings as well as in slide films for anti-static applications. 20

21 INFLUENCE OF TIMREX GRAPHITE AND COKE FILLERS IN FILLED-PTFE Wear resistance Virgin PTFE shows much high wear as a result of the destruction of the banded structure due to easy slippage between the crystalline lamellae in the bands. The presence of well distributed carbon particles in the filled PTFE partially avoid the slippage between the crystalline lamellae in the bands and therefore the wear resistance is improved. TYPICAL APPLICATIONS FOR TIMREX GRAPHITE AND COKE Deformation strength Virgin PTFE deformation behaviour is somehow similar to the mechanism previously described. In someway the deformation phenomena could be explained by the tendency of slippage that occurs between the crystalline lamellae. However, in this case the presence of well distributed carbon particles in the filled PTFE offers only a partial explanation to the phenomena because also hardness of these particles is important in determine an improvement of the deformation behaviour. Friction coefficient The coefficient of friction for various filled PTFE composites is weakly dependent upon the incorporated filler, because a thin PTFE film generally exists at the interface between the body and counter-body. Consequently the coefficient of friction is both similar in the filled PTFE and virgin PTFE. This evidence is true as long as no oversize particles are present in the filler. In fact the presence of oversize particles could lead to a radically modification of the coefficient of friction. Because of that in carbons as well as in other fillers is very important the control of oversize particles. 21

22 Thermally conductive polymers TYPICAL APPLICATIONS FOR TIMREX GRAPHITE AND COKE WHAT IS THERMAL CONDUCTIVITY? THERMAL CONDUCTIVITY OF GRAPHITE The ability of a material to conduct heat is known as its thermal conductivity. Thermal conductivity itself is nothing else than the transportation of thermal energy from high to low temperature regions. Thermal energy within a crystalline solid is conducted by electrons and/or discrete vibrational energy packets (phonons*). Each effect, phonons and movement of free electrons, contributes to the rate at which thermal energy moves. Generally, either free electrons or phonons predominate in the system. *Phonons In the crystalline structures of a solid material, atoms excited into higher vibrational frequency impart vibrations into adjacent atoms via atomic bonds. This coupling creates waves which travel through the lattice structure of a material. In solid materials these lattice waves, or phonons, travel at the velocity of sound. During thermal conduction it is these waves which aid in the transport of energy. Graphite is an excellent solution for making polymers thermally conductive when electrical conductivity is also tolerated. Graphite operates by a phonon collision mechanism, very different from the percolation mechanism occurring with metallic powders. This mechanism, together with the particular morphology of graphite particles, helps to meet the required thermal conductivity at lower additive levels without any abrasion issues. In addition, due to its particular structure, thermal conductivity is different in the different directions of the crystal. It is highly conducting along its layers (ab direction or in-plane) and less conducting perpendicular to the layers (c direction or through-plane) because there is no bonding between the layers. In particular, expanded graphite is well known as an excellent thermally and electrically conductive additive for polymers. On the way to graphene, high aspect ratio expanded graphite is thermally more conductive when compared to conventional carbon materials such as standard graphite and carbon fibres. However, the very low bulk density of expanded graphite makes it very difficult to feed into a polymer melt using common feeding/mixing technologies. In order to overcome the feed issues encountered by compounders with expanded graphite, Imerys Graphite & Carbon has developed a range of products belonging to the TIMREX C-THERM carbon-based product family. GRADE FEATURES FORM ASH CONTENT (%) TIMREX KS family Standard (spheroids) EFFECT ON THERMAL CONDUCTIVITY powder < 0.1 medium (through-plane +) TIMREX SFG family Standard (flakes) powder < 0.1 medium (in-plane +) TIMREX C-THERM 011 High aspect ratio (pure) soft granules < 2.5 high TIMREX C-THERM 001 High aspect ratio (pure +) soft granules < 0.3 high 22

23 THERMALLY CONDUCTIVE POLYMERS Thermally conductive polymers are able to evenly distribute heat generated internally from a device and eliminate hot spots. Possible applications for thermally conductive plastics include heat sinks, geothermal pipes, LED light sockets, heat exchangers, appliance temperature sensors and many other industrial applications. Also thermally conductive elastomers can be found in a wide variety of industrial applications such as gaskets, vibration dampening, interface materials, and heat sinks. As highlighted in the figure, the low thermal conductivity of virgin PPH (~0.38 W/m.K) could be increased by one order of magnitude already at relatively low addition level (~3.5 W/m.K at 20% C-THERM ). The through-plane thermal conductivity is about the half of the longitudinal in-plane thermal conductivity. These results indicate that the anisotropy of the graphite particles is conferred to the final compound, due to their alignment during the injection molding process. This is an important property that has to be taken into account by design engineers. Of course, the thermal conductivity strongly depends not only on the sample orientation (direction) during the measurement, but also on the type of polymer, the sample history (type and conditions of compounding and processing) and the measurement method. A full set of measurements to determine mechanical properties in PP were performed and are available to customers. When tested at the same loadings, C-THERM imparts similar mechanical properties as conventional carbon materials. Thermal conductivity (W/m.K) 4.0 In-plane 3.5 inj > In-plane Through-plane 3.0 Through-plane Virgin PPH 20% 20% ENSACO TIMREX 250G KS25 20% TIMREX C-THERM TYPICAL APPLICATIONS FOR TIMREX GRAPHITE AND COKE 23

24 EUROPE Imerys Graphite & Carbon Switzerland Ltd. Group Head Office Strada Industriale Bodio Switzerland Tel: Fax: Imerys Graphite & Carbon Belgium SA Brownfieldlaan Willebroek Belgium Tel: Fax: [email protected] Imerys Graphite & Carbon Germany GmbH Berliner Allee Düsseldorf Germany Tel: Fax: [email protected] France Representative Office c/o Imerys rue de l Université Paris France Tel: /91 Fax: [email protected] 24 UK Representative Office Tel: Fax: [email protected] ASIA-PACIFIC Imerys Graphite & Carbon Japan K.K. Tokyo Club Building 13F Kasumigaseki Chiyoda-ku Tokyo Japan Tel: Fax: [email protected] Imerys Graphite & Carbon (Changzhou) Co. Ltd. 188# Taishan Road Hi-Tech Zone Changzhou China Tel: Fax: [email protected] Shanghai Branch Office c/o Imerys 288, Jiu Jiang Road Hong Yi Plaza Unit Shanghai China Tel: Fax: [email protected] Singapore Representative Office c/o Imerys Asia Pacific 80 Robinson Road # Singapore Tel: Fax: [email protected] AMERICAS Imerys Graphite & Carbon USA Inc Clemens Road 1-L Westlake (OH) USA Tel: Fax: [email protected] Imerys Graphite & Carbon Canada Inc. 990 rue Fernand-Poitras Terrebonne (QC) J6Y 1V1 Canada Tel: Fax: [email protected] Imerys Graphite & Carbon is a trademark of the Imerys Group 2014 Imerys Graphite & Carbon CH-Bodio. No part of this publication may be reproduced in any form without the prior written authorisation.