Chris Rauwendaal. Polymer Extrusion. 5 th Edition

Transcription

1 Chris Rauwendaal Polymer Extrusion 5 th Edition

2 Rauwendaal Polymer Extrusion

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4 Chris Rauwendaal Polymer Extrusion 5th Edition With contributions from Paul J. Gramann, Bruce A. Davis, and Tim A. Osswald Hanser Publishers, Munich Hanser Publications, Cincinnati

5 The Author: Dr. Chris Rauwendaal Combie Road # 6677, Auburn, CA , USA Distributed in North and South America by: Hanser Publications 6915 Valley Avenue, Cincinnati, Ohio , USA Fax: (513) Phone: (513) Distributed in all other countries by Carl Hanser Verlag Postfach , München, Germany Fax: +49 (89) The use of general descriptive names, trademarks, etc., in this publication, even if the former are not especially identified, is not to be taken as a sign that such names, as understood by the Trade Marks and Merchandise Marks Act, may accordingly be used freely by anyone. While the advice and information in this book are believed to be true and accurate at the date of going to press, neither the author nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made. The publisher makes no warranty, express or implied, with respect to the material contained herein. Library of Congress Cataloging-in-Publication Data Rauwendaal, Chris. Polymer extrusion / Chris Rauwendaal. -- 5th edition. pages cm ISBN (hardcover) -- ISBN (e-book) 1. Plastics--Extrusion. I. Title. TP1175.E9R dc Bibliografische Information Der Deutschen Bibliothek Die Deutsche Bibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografie; detaillierte bibliografische Daten sind im Internet über < abrufbar. ISBN E-Book ISBN All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying or by any information storage and retrieval system, without permission in writing from the publisher. Carl Hanser Verlag, Munich 2014 Production Management: Steffen Jörg Coverconcept: Marc Müller-Bremer, München Coverdesign: Stephan Rönigk Typsetted, printed and bound by Kösel, Krugzell Printed in Germany

6 Preface to the Fifth Edition It has been twelve years since the fourth edition of Polymer Extrusion was published and twenty six years since the book was first published. Extrusion technology continues to advance; as a result, a fifth edition is needed to keep the Polymer Extrusion book up to date and relevant. New material has been added throughout the book. The general literature survey has been updated since several books on extrusion have been published since A new theory for predicting developing melt temperatures has been incorporated into Chapter 7. This theory allows accurate prediction of changes in melt temperature along the length of the extruder; complete analytical solutions are presented to the relevant equations. As a result, melt temperatures can be predicted without having to result to numerical techniques and computer simulation. In Chapter 8, a new section on efficient extrusion of medical devices has been added. It covers good manufacturing practices in medical extrusion and automation. The effect of processing conditions and screw design on molecular degradation is covered in detail. Screws designs that minimize molecular degradation are discussed and explained. In Chapter 11, the section on gels in extruded products has been expanded as this continues to be a problem experienced by many extrusion companies. There is also a new section on discolored specks in extruded products. In this section expressions are included that allow prediction of the incidence and frequency of specks or gels based on their frequency in the incoming raw material. Included is a discussion on new instruments that are now available to detect defects in pellets produced at the resin supplier with the ability to remove pellets with defects from the pellet stream. Over the past five to ten years very high speed single screw extruders have been developed. These extruders are now commercially available and they are used by dozens of companies around the world. These machines run at speeds up to 1500 rpm; they achieve outputs that are about an order of magnitude above those of conventional extruders. This high speed single screw extruder technology is one of the most significant developments. Therefore, this topic has been added to the new edition in Chapter 2.

7 VI Preface to the Fifth Edition The author would like to thank Professor Jürgen Miethlinger and Michael Aigner from Johannes Kepler University in Linz, Austria for checking equations in Chapter 7 and finding a few mistakes; these have been corrected. The author would also like to thank Cheryl Hamilton and Nadine Warkotsch at Carl Hanser Verlag for their encouragement and help in making the fifth edition a reality. The author is grateful for a long and fruitful relationship with Carl Hanser Verlag. Finally, I would like to extend a special thank you to my wife Sietske. She has supported and helped me in many ways for the past forty years. I am grateful for her love and support I feel very fortunate to have a friend and spouse who makes life worth living. Chris Rauwendaal Auburn, California October 2013

8 Contents Preface to the Fifth Edition V 1 Introduction Basic Process Scope of the Book General Literature Survey History of Polymer Extrusion Part I Extrusion Machinery Different Types of Extruders The Single Screw Extruder Basic Operation Vented Extruders Rubber Extruders High-Speed Extrusion Melt Temperature Extruders without Gear Reducer Energy Consumption Change-over Resin Consumption Change-over Time and Residence Time The Multiscrew Extruder The Twin Screw Extruder The Multiscrew Extruder With More Than Two Screws The Gear Pump Extruder Disk Extruders Viscous Drag Disk Extruders Stepped Disk Extruder Drum Extruder Spiral Disk Extruder Diskpack Extruder The Elastic Melt Extruder Overview of Disk Extruders Ram Extruders Single Ram Extruders Solid State Extrusion Multi Ram Extruder

9 VIII Contents Appendix Pumping Efficiency in Diskpack Extruder Extruder Hardware Extruder Drive AC Motor Drive System Mechanical Adjustable Speed Drive Electric Friction Clutch Drive Adjustable Frequency Drive DC Motor Drive System Brushless DC Drives Hydraulic Drive System Comparison of Various Drive Systems Reducer Constant Torque Characteristics Thrust Bearing Assembly Barrel and Feed Throat Feed Hopper Extruder Screw Die Assembly Screens and Screen Changers Heating and Cooling Systems Electric Heating Resistance Heating Induction Heating Fluid Heating Extruder Cooling Screw Heating and Cooling Instrumentation and Control Instrumentation Requirements Most Important Parameters Pressure Measurement The Importance of Melt Pressure Different Types of Pressure Transducers Mechanical Considerations Specifications Comparisons of Different Transducers Temperature Measurement Methods of Temperature Measurement Barrel Temperature Measurement Stock Temperature Measurement Ultrasound Transmission Time Infrared Melt Temperature Measurement Other Measurements Power Measurement

10 Contents Rotational Speed Extrudate Thickness Extrudate Surface Conditions Temperature Control On-Off Control Proportional Control Proportional-Only Control Proportional and Integral Control Proportional and Integral and Derivative Control Dual Sensor Temperature Control Controllers Temperature Controllers Power Controllers Dual Output Controllers Time-Temperature Characteristics Thermal Characteristics of the System Modeling of Response in Linear Systems Temperature Characteristics with On-Off Control Tuning of the Controller Parameters Performance Criteria Effect of PID Parameters Tuning Procedure When Process Model Is Unknown Tuning Procedure When Process Model Is Known Pre-Tuned Temperature Controllers Self-Tuning Temperature Controllers Total Process Control True Total Extrusion Process Control Part II Process Analysis Fundamental Principles Balance Equations The Mass Balance Equation The Momentum Balance Equation The Energy Balance Equation Basic Thermodynamics Rubber Elasticity Strain-Induced Crystallization Heat Transfer Conductive Heat Transfer Convective Heat Transfer Dimensionless Numbers Dimensional Analysis Important Dimensionless Numbers Viscous Heat Generation Radiative Heat Transport Dielectric Heating Microwave Heating IX

11 X Contents 5.4 Basics of Devolatilization Devolatilization of Particulate Polymer Devolatilization of Polymer Melts Appendix Example: Pipe Flow of Newtonian Fluid Important Polymer Properties Properties of Bulk Materials Bulk Density Coefficient of Friction Particle Size and Shape Other Properties Melt Flow Properties Basic Definitions Power Law Fluid Other Fluid Models Effect of Temperature and Pressure Viscoelastic Behavior Measurement of Flow Properties Capillary Rheometer Melt Index Tester Cone and Plate Rheometer Slit Die Rheometer Dynamic Analysis Thermal Properties Thermal Conductivity Specific Volume and Morphology Specific Heat and Heat of Fusion Specific Enthalpy Thermal Diffusivity Melting Point Induction Time Thermal Characterization DTA and DSC TGA TMA Other Thermal Characterization Techniques Polymer Property Summary Functional Process Analysis Basic Screw Geo metry Solids Conveying Gravity Induced Solids Conveying Pressure Distribution Flow Rate Design Criteria

12 Contents Drag Induced Solids Conveying Frictional Heat Generation Grooved Barrel Sections Adjustable Grooved Barrel Extruders Starve Feeding Versus Flood Feeding Plasticating Theoretical Model of Contiguous Solids Melting Non-Newtonian, Non-Isothermal Case Other Melting Models Power Consumption in the Melting Zone Computer Simulation Dispersed Solids Melting Melt Conveying Newtonian Fluids Effect of Flight Flanks Effect of Clearance Power Consumption in Melt Conveying Power Law Fluids One-Dimensional Flow Two-Dimensional Flow Non-Isothermal Analysis Newtonian Fluids with Negligible Viscous Dissipation Non-Isothermal Analysis of Power Law Fluids Developing Temperatures Estimating Fully Developed Melt Temperatures Assumption of Stationary Screw and Rotating Barrel Die Forming Velocity and Temperature Profiles Extrudate Swell Die Flow Instabilities Shark Skin Melt Fracture Draw Resonance Devolatilization Mixing Mixing in Screw Extruders Distributive Mixing in Screw Extruders Static Mixing Devices Geo metry of Static Mixers Functional Performance Characteristics Miscellaneous Considerations Dispersive Mixing Solid-Liquid Systems Liquid-Liquid System Backmixing Cross-Sectional Mixing and Axial Mixing XI

13 XII Contents Residence Time Distribution RTD in Screw Extruders Methods to Improve Backmixing Conclusions for Backmixing Appendix Appendix Appendix Extruder Screw Design Mechanical Considerations Torsional Strength of the Screw Root Strength of the Screw Flight Lateral Deflection of the Screw Optimizing for Output Optimizing for Melt Conveying Optimizing for Plasticating Effect of Helix Angle Effect of Multiple Flights Effect of Flight Clearance Effect of Compression Ratio Optimizing for Solids Conveying Effect of Channel Depth Effect of Helix Angle Effect of Number of Flights Effect of Flight Clearance Effect of Flight Geometry Optimizing for Power Consumption Optimum Helix Angle Effect of Flight Clearance Effect of Flight Width Single-Flighted Extruder Screws The Standard Extruder Screw Modifications of the Standard Extruder Screw Devolatilizing Extruder Screws Functional Design Considerations Various Vented Extruder Screw Designs Conventional Vented Extruder Screw Bypass Vented Extruder Screw Rearward Devolatilization Multi-Vent Devolatilization Cascade Devolatilization Venting through the Screw Venting through a Flighted Barrel Vent Port Configuration Multi-Flighted Extruder Screws The Conventional Multi-Flighted Extruder Screw

14 Contents Barrier Flight Extruder Screws The Maillefer Screw The Barr Screw The Dray and Lawrence Screw The Kim Screw The Ingen Housz Screw The CRD Barrier Screw Summary of Barrier Screws Mixing Screws Dispersive Mixing Elements The CRD Mixer Mixers to Break Up the Solid Bed Summary of Dispersive Mixers Distributive Mixing Elements Ring or Sleeve Mixers Variable Depth Mixers Summary of Distributive Mixers Efficient Extrusion of Medical Devices Introduction Good Manufacturing Practices in Medical Extrusion Automation of the Medical Extrusion Process Minimizing Polymer Degradation Melt Temperatures Inside the Extruder Melt Temperatures and Screw Design Molecular Degradation and Screw Design Conclusions Scale-Up Common Scale-Up Factors Scale-Up for Heat Transfer Scale-Up for Mixing Comparison of Various Scale-Up Methods Rebuilding Worn Screws and Barrels Application of Hardfacing Materials Oxyacetylene Welding Tungsten Inert Gas Welding Plasma Transfer Arc Welding Metal Inert Gas Welding Laser Hardfacing Rebuilding of Extruder Barrels Die Design Basic Considerations Balancing the Die by Adjusting the Land Length Balancing by Channel Height Other Methods of Die Balancing XIII

15 XIV Contents Film and Sheet Dies Flow Adjustment in Sheet and Film Dies The Horseshoe Die Pipe and Tubing Dies Tooling Design for Tubing Definitions of Various Draw Ratios Land Length Taper Angles Special Features Blown Film Dies The Spiral Mandrel Geometry Effect of Die Geometry on Flow Distribution Summary of Spiral Mandrel Die Design Variables Profile Extrusion Dies Coextrusion Interface Distortion Calibrators Twin Screw Extruders Introduction Twin versus Single Screw Extruder Intermeshing Co-Rotating Extruders Closely Intermeshing Extruders Self-Wiping Extruders Geometry of Self-Wiping Extruders Conveying in Self-Wiping Extruders Intermeshing Counter-Rotating Extruders Non-Intermeshing Twin Screw Extruders Coaxial Twin Screw Extruders Devolatilization in Twin Screw Extruders Commercial Twin Screw Extruders Screw Design Issues for Co-Rotating Twin Screw Extruders Scale-Up in Co-Rotating Twin Screw Extruders Overview of Twin Screw Extruders Troubleshooting Extruders Requirements for Efficient Troubleshooting Instrumentation Understanding of the Extrusion Process Collect and Analyze Historical Data (Timeline) Team Building Condition of the Equipment Information on the Feedstock Tools for Troubleshooting Temperature Measurement Devices