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Rauwendaal Polymer Extrusion 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 The Author: Dr. Chris Rauwendaal 10556 Combie Road # 6677, Auburn, CA 95602-8908, USA Dist...

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Rauwendaal Polymer Extrusion

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

The Author: Dr. Chris Rauwendaal 10556 Combie Road # 6677, Auburn, CA 95602-8908, USA

Distributed in North and South America by: Hanser Publications 6915 Valley Avenue, Cincinnati, Ohio 45244-3029, USA Fax: (513) 527-8801 Phone: (513) 527-8977 www.hanserpublications.com Distributed in all other countries by Carl Hanser Verlag Postfach 86 04 20, 81631 München, Germany Fax: +49 (89) 98 48 09 www.hanser-fachbuch.de 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 978-1-56990-516-6 (hardcover) -- ISBN 978-1-56990-539-5 (e-book) 1. Plastics--Extrusion. I. Title. TP1175.E9R37 2013 668.4’13--dc23 2013037810 Bibliografische Information Der Deutschen Bibliothek Die Deutsche Bibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografie; detaillierte bibliografische Daten sind im Internet über abrufbar. ISBN 978-1-56990-516-6 E-Book ISBN 978-1-56990-539-5 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, www.rebranding.de, München Coverdesign: Stephan Rönigk Typsetted, printed and bound by Kösel, Krugzell Printed in Germany

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 2001. 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.

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

Contents Preface to the Fifth Edition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 1.2 1.3 1.4

Basic Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scope of the Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General Literature Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . History of Polymer Extrusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 2 3 6

Part I – Extrusion Machinery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2 Different Types of Extruders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.1

2.2

2.3

2.4

The Single Screw Extruder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.1.1 Basic Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.1.2 Vented Extruders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.1.3 Rubber Extruders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.1.4 High-Speed Extrusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.1.4.1 Melt Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.1.4.2 Extruders without Gear Reducer . . . . . . . . . . . . . . . . . . . . . . . . . 23 2.1.4.3 Energy Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 2.1.4.4 Change-over Resin Consumption . . . . . . . . . . . . . . . . . . . . . . . . . 23 2.1.4.5 Change-over Time and Residence Time . . . . . . . . . . . . . . . . . . . . 24 The Multiscrew Extruder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2.2.1 The Twin Screw Extruder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2.2.2 The Multiscrew Extruder With More Than Two Screws . . . . . . . . . . . . . . 25 2.2.3 The Gear Pump Extruder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Disk Extruders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 2.3.1 Viscous Drag Disk Extruders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 2.3.1.1 Stepped Disk Extruder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 2.3.1.2 Drum Extruder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 2.3.1.3 Spiral Disk Extruder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 2.3.1.4 Diskpack Extruder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 2.3.2 The Elastic Melt Extruder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 2.3.3 Overview of Disk Extruders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Ram Extruders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 2.4.1 Single Ram Extruders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 2.4.1.1 Solid State Extrusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 2.4.2 Multi Ram Extruder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

VIII Contents

2.4.3 Appendix 2.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 2.4.3.1 Pumping Efficiency in Diskpack Extruder . . . . . . . . . . . . . . . . . . 42

3

Extruder Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Extruder Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.1 AC Motor Drive System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.1.1 Mechanical Adjustable Speed Drive . . . . . . . . . . . . . . . . . . . . . . . 3.1.1.2 Electric Friction Clutch Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.1.3 Adjustable Frequency Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.2 DC Motor Drive System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.2.1 Brushless DC Drives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.3 Hydraulic Drive System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.4 Comparison of Various Drive Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.5 Reducer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.6 Constant Torque Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Thrust Bearing Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Barrel and Feed Throat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Feed Hopper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 Extruder Screw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 Die Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.1 Screens and Screen Changers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7 Heating and Cooling Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.1 Electric Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.1.1 Resistance Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.1.2 Induction Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.2 Fluid Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.3 Extruder Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.4 Screw Heating and Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

49 49 49 50 50 51 53 55 55 58 59 60 61 64 68 70 72 72 75 75 75 76 77 77 80

4

85 85 86 87 87 88 92 93 96 96 97 100 102 105 106 107 107

Instrumentation and Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Instrumentation Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.1 Most Important Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Pressure Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 The Importance of Melt Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.2 Different Types of Pressure Transducers . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.3 Mechanical Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.4 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.5 Comparisons of Different Transducers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Temperature Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.1 Methods of Temperature Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2 Barrel Temperature Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.3 Stock Temperature Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.3.1 Ultrasound Transmission Time . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.3.2 Infrared Melt Temperature Measurement . . . . . . . . . . . . . . . . . . 4.4 Other Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.1 Power Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contents IX

4.4.2 Rotational Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.3 Extrudate Thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.4 Extrudate Surface Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Temperature Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.1 On-Off Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.2 Proportional Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.2.1 Proportional-Only Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.2.2 Proportional and Integral Control . . . . . . . . . . . . . . . . . . . . . . . . 4.5.2.3 Proportional and Integral and Derivative Control . . . . . . . . . . . . 4.5.2.4 Dual Sensor Temperature Control . . . . . . . . . . . . . . . . . . . . . . . . 4.5.3 Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.3.1 Temperature Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.3.2 Power Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.3.3 Dual Output Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.4 Time-Temperature Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.4.1 Thermal Characteristics of the System . . . . . . . . . . . . . . . . . . . . 4.5.4.2 Modeling of Response in Linear Systems . . . . . . . . . . . . . . . . . . . 4.5.4.3 Temperature Characteristics with On-Off Control . . . . . . . . . . . . 4.5.5 Tuning of the Controller Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.5.1 Performance Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.5.2 Effect of PID Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.5.3 Tuning Procedure When Process Model Is Unknown . . . . . . . . . 4.5.5.4 Tuning Procedure When Process Model Is Known . . . . . . . . . . . 4.5.5.5 Pre-Tuned Temperature Controllers . . . . . . . . . . . . . . . . . . . . . . . 4.5.5.6 Self-Tuning Temperature Controllers . . . . . . . . . . . . . . . . . . . . . . 4.6 Total Process Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.1 True Total Extrusion Process Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

109 110 114 116 117 119 119 123 124 125 126 126 126 128 128 128 130 133 135 135 136 137 138 139 140 140 141

Part II – Process Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 5 Fundamental Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 5.1 Balance Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.1 The Mass Balance Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.2 The Momentum Balance Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.3 The Energy Balance Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Basic Thermodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.1 Rubber Elasticity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.2 Strain-Induced Crystallization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Heat Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.1 Conductive Heat Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.2 Convective Heat Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.3 Dimensionless Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.3.1 Dimensional Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.3.2 Important Dimensionless Numbers . . . . . . . . . . . . . . . . . . . . . . . 5.3.4 Viscous Heat Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.5 Radiative Heat Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.5.1 Dielectric Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.5.2 Microwave Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

149 149 150 151 153 157 159 160 160 161 161 161 163 168 169 171 173

X

Contents

5.4 Basics of Devolatilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 5.4.1 Devolatilization of Particulate Polymer . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 5.4.2 Devolatilization of Polymer Melts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 Appendix 5.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 Example: Pipe Flow of Newtonian Fluid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

6

Important Polymer Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Properties of Bulk Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.1 Bulk Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.2 Coefficient of Friction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.3 Particle Size and Shape . . . . . . . . . . . . . . . . . . . . . . . . . . . ...