Polymer Products

DESIGN, MATERIALS AND PROCESSING

Polymer Products

DESIGN, MATERIALS AND PROCESSING

David H. Morton-Jones Dowty Research Fellow University of Lancaster

John W Ellis Formerly Senior Lecturer in Plastics Engineering

Singapore Polytechnic

LONDON NEW YORK CHAPMAN AND HALL

First published in 1986 by Chapman and Hall Ltd

11 New Fetter Lane, London EC4P 4EE Published in the USA by

Chapman and Hall 29 West 35th Street, New York NY 10001

© 1986 D. H. Morton-Jones and J W Ellis

Softcover reprint of the hardcover 1 st edition 1986

All rights reserved. No part of this book may be reprinted, or reproduced or utilized in any form or by any electronic, mechanical or other means, now know

or hereafter invented, including photocopying and recording, or in any information storage and retrieval

system, without permission in writing from the publisher.

British Library Cataloguing in Publication Data

Morton-Jones, D. H. Polymer products: design, materials and processing. 1. Polymers and polymerization 1. Title II. Ellis, J W 620.1'92 TA455.P58

Library of Congress Cataloging in Publication Data

Morton-Jones, D. H (David H), 1931-Polymer products

Bi,bliography: p. Includes index. 1. Polymers and polymerization. 1. Ellis, J W Oohn W), 1941- II. Title. TA455.P58M64 1986 668.9 85-22420

ISBN-13: 978-94-010-8320-1 e-ISBN-13: 978-94-009-4101-4 DOl: 10 .1007/978-94-009-410 1-4

This book is dedicated to Roy Smith, our mentor in the original

Case-studies project

Preface Acknowledgements List of Participating Companies

CONTENTS

PST 1: Injection Moulding and its Materials

1.1 Injection moulding 1.2 Amorphous and crystalline polymers 1.3 Polymers in the rubber state 1.4 Environmental stress cracking 1.5 Creep in polymers

2 Optimizing Injection Moulding Conditions

2.1 Introduction 2.2 Support bracket 2.3 Film spool end 2.4 Comment on importance of process 2.5 Control features in injection moulding 2.6 The case for the programmed machine

3 Some Examples of Polymer Selection

3.1 Combination nozzle for Electrolux cleaner 3.2 Impellor for Flymo hover mower 3.3 Flymo mower hood 3.4 Motor housing in vacuum cleaner 3.5 Moulding conditions 3.6 Polymer science aspects: polymers in the rubber state

4 Plastics Gears

4.1 Introduction 4.2 The GEC reduction gear box 4.3 Why plastics gears? 4.4 Methods for making plastics gears 4.5 Design of moulded gears 4.6 Materials 4.7 Design development of office copier gearbox 4.8 Injection moulding of gears 4.9 References

xiii xiv xv

1 5 7 9 9

13

13 13 19 24 24 32

33

33 36 38 39 40 41

42

42 43 44 44 45 56 59 63 64

Contents

5 Acetal Clips for Roof Tiles

5.1 Introduction 5.2 The mark 9 clip 5.3 Loading calculations 5.4 Production and quality control

6 Acetal Spring for Selector Switch

6.1 Introduction 6.2 Development of the acetal spring 6.3 Evaluation and testing 6.4 Polymer and processing 6.5 Comment on design and polymer properties

7 PST 2: Foam Cored Mouldings

7.1 Structural foam 7.2 Comparison of the sandwich moulding and structural

foam processes 7.3 The sandwich moulding process 7.4 Relative merits of compact moulding

8 Structural Foam Trolley Base

8.1 Introduction 8.2 Design brief 8.3 Material and manufacturing process selection 8.4 Design procedure 8.5 The moulding process 8.6 References

9 Washing Machine Tank in Glass-coupled Polypropylene Structural Foam

9.1 Introduction 9.2 Background 9.3 Operating conditions of the tank 9.4 Materials and process selection 9.5 Design features 9.6 The mould 9.7 The moulding machine 9.8 Processing conditions 9.9 Secondary operation 9.10 Testing

10 Sandwich Moulded TV Screen Frame

10. 1 Synopsis

viii

10.2 Design of the moulded TV front 10.3 Production details 10.4 Tests of finished product 10.5 Some other aspects of SM 10.6 Sandwich moulded toilet cisterns 10.7 UK involvement in SM

65

65 65 67 69

70

70 70 74 75 77

78

78

89 90 90

94

94 95 96 97 99

101

102

102 103 103 103 106 108 108 108 109 109

111

111 111 114 116 116 117 118

11 PST 3: Polyurethanes

11.1 Introduction 11.2 Basic reactions 11.3 Materials 11.4 Relationships between structure and properties 11.5 Polyurethane foam

12 Reinforced Reaction Injection Moulding (RRIM)

12.1 Introduction 12.2 Polyurethane systems 12.3 Development of short glass-fibre reinforcement 12.4 RRIM development 12.5 The RRIM process

13 Polyurethane Shoe Soles

13.1 Introduction 13.2 Shoe manufacture - historical 13.3 Development of the PU sole 13.4 Polyurethane materials 13.5 PU shoe soling 13.6 Manufacture 13.7 Product testing 13.8 Design considerations 13.9 References

14 Printed Gaskets in Hydraulic Control Equipment

14.1 Background 14.2 The hydraulic control valve 14.3 The printed gasket 14.4 Polyurethane seal 14.5 Selection of materials 14.6 Production of the printed gasket 14.7 Testing and quality control 14.8 Failure in printed gaskets 14.9 Development of new specifications 14.10 Future Developments

IS PST 4: Glass-reinforced Plastics (GRP)

15.1 Introduction 15.2 Reinforcing fibres 15.3 Unsaturated polyester resins 15.4 The hand lay-up process 15.5 Sheet moulding compound (SMC) 15.6 Disadvantage of SMC Moulding Compared with

Hand Lay-up 15.7 Stiffness of materials (with reference to GRP) 15.8 Plastics vehicle bodies

Contents

119

119 120 122 125 125

127

127 127 127 129 130

133

133 133 135 138 138 141 143 145 146

147

147 147 147 147 150 150 154 155 155 158

159

159 160 161 162 164

166 167 169

ix

Contents

16 GRP-Clad Lorry Cab

16.1 General description 16.2 Design considerations 16.3 Materials selection 16.4 Production details 16.5 Testing 16.6 Summary of costs 16.7 References

17 High Speed Train Cab

17.1 Introduction 17.2 Design considerations 17.3 Materials 17.4 Production details

18 DMC Vehicle Headlamps

18.1 Introduction 18.2 Historical 18.3 Material selection 18.4 Some design aspects 18.5 Quality and performance aspects 18.6 Technical appendix {Lucas} 18.7 Manufacture 18.8 The test programme

19 'Fiberlam' Aircraft Flooring

19.1 General description of 'Fiberlam' 19.2 Materials 19.3 Manufacturing aspects 19.4 Some product features 19.5 Testing 19.6 History of sandwich structures in aircraft flooring 19.7 References

20 PST 5: Rubbers

20.1 Natural and synthetic rubbers 20.2 Polychloroprene rubber 20.3 Vulcanization

21 Rubber-Steel Conveyor Belt

21.1 Introduction

x

21.2 Background 21.3 The development of steel cord belting 21.4 Development of the Selby conveyor 21.5 Manufacture 21.6 Product testing 21. 7 Installation 21.8 References

173

173 173 178 179 182 182 183

184

184 184 191 192

196

196 197 198 200 203 204 206 209

211

211 211 214 215 217 217 220

221

221 222 223

226

226 226 227 233 237 244 250 251

22 The Blow Moulding Process

22.1 Introduction 22.2 Blow moulding of large containers 22.3 Injection blow moulding

23 The Acitainer Blow Moulded Acid Container

23.1 Introduction 23.2 Design considerations 23.3 Material selection 23.4 Production details 23.5 References

24 Chemical Effluent Pipe in HOPE

24.1 Introduction 24.2 Effluents 24.3 Selection of materials 24.4 Design factors 24.5 Manufacture and assembly 24.6 Quality control and testing 24.7 Pressure pipe - pressure rating calculation 24.8 Static loads in buried pipe 24.9 Appendix: Crack Propagation

25 Failure of a Polypropylene Vessel

25.1 Introduction 25.2 The plant 25.3 The failure incident 25.4 Examination of fractured pipe 25.5 Investigation 25.6 Fracture calculations 25.7 Bubble collapse 25.8 Conclusion 25.9 Remedial action

26 Heat Shrinkable Terminations for Power Cables

26.1 Introduction 26.2 Heat-shrinkable plastics 26.3 Power cables 26.4 Termination by tradi tiona I methods 26.5 Application of heat-shrinkable plastks in MV 26.6 Heat-shrinkable plastics in high voltage applications 26.7 Stress grading 26.8 Non-tracking outer insulation 26.9 High voltage non-track material (HVTM) 26.10 Sealant 26.11 The development programme 26.12 References

Index

Contents

252

252 253 254

255

256 258 263 267 269

270

270 270 270 275 276 281 284 287 293

295

295 295 297 298 298 299 303 304 304

305

305 306 308 309 310 310 311 317 330 334 334 335

337

xi

PREFACE

This book is derived from a recent project sponsored by the Polymer Engineering Directorate of the SERC and carried out at the University of Lancaster under the joint auspices of the Departments of Chemistry and Engineering. The project set out to provide a novel type of teaching material for introducing polymers and their uses to students, especially of engineering. Case studies of real examples of polymers at work are used, so the student or teacher can start with a successful and well-designed product and work backwards to its origins in the market, in design and material selection and in the manufacturing process. The philosophy is that such an approach captures interest right at the start by means of a real example and then retains it because of the relevance of the technical explanation. This after all is what most of us do habitually; we turn to examples to make our point. The hope is that subject matter with a somewhat notorious reputation among engineers, such as aspects of polymer chemistry and the non-linear behaviour of polymers under mechanical loading will be fairly painlessly absorbed through the context of the examples.

Each study becomes a separate chapter in the book. The original studies, and hence the present chapters, vary in length because different topics demanded different approaches. No attempt has been made to alter this, or to adopt a standardized format because to have done so would have interfered with the vitality of the original work.

The studies have been ordered into a number of technological groups, each of which is preceded by a chapter on the relevant polymer science and technology: these are the 'PST' chapters. Many of the original studies contained such a section but to have retained them intact would have entailed undue repetition. Their assembly into separate chapters in the present work form a collection of articles on topics in polymer science and technology which it is hoped will prove useful as a sub-theme to the case-study material. In a few cases polymer science aspects have been left in their original contexts because they seemed particularly relevant or were intimately bound up with the product development. Examples are found in the chapter on Heat Shrinkable Power Cable Termination where the technology of these materials is special to the study, and the Acitainer

Preface

study which includes some general remarks and tables about material selection as well as those relevant to the product itself. Similarly, the chapter on Fibrelam includes general remarks about aramid fibres as well as those specific to the product.

The book does not pretend to be a comprehensive account of polymer technology. Rather it aims to whet the appetite. If it leads the reader to generate his own new case studies from local industries or makes more palatable the more formal works on polymers it will have served its purpose.

Eight of the studies were composed by John Ellis, who was the first Polymer Applications Fellow at Lancaster, and the remainder by myself. I am responsible for any editing errors which have persisted into the final version.

Lancaster April 1986

ACKNOWLEDGMENTS

D.H.M-J.

I should like to acknowledge warmly the unstinted cooperation offered by the companies whose products and processes form the subject matter of the book. Throughout, their interest and enthusiasm was outstanding. A list of companies appears below. Also, I must acknowledge the invaluable efforts of Sue Cameron who prepared the camera-ready copy for the book, and my daughter Gillian Morton-Jones who prepared the drawings for the studies.

D.H.M-J.

xiv

LIST OF PARTICIPATING COMPANIES

BTR Bel ting Ltd BIP Ltd Bifort Engineering Ltd W.H. Boddington Ltd Bri tish Rail Engineering C.I. Polymers Ltd Ciba-Geigy Ltd Clarks Ltd Davall Moulded Gears Ltd Dowty Seals Ltd Thomas Dudley Ltd Elco Plastics Ltd ERF Ltd Flymo Manufacturing Ltd Geest Industries Ltd Harcoster Ltd J.J. Harvey Ltd ICI Pic Lucas Electrical Ltd Philips Domestic Appliances Plastics Processing Industries Training Board Raychem Ltd Scott Bader Company Ltd Thorn Consumer Electronics Ltd