Plastics Engineering 3E Episode 1 pps

tL A- * PLASTICS ENGINEERING PLASTICS ENGINEERING Third Edition R.J. Crawford, BSc, PhD, DSc, FEng, FIMechE, FIM Department of Mechanical, Aeronautical and Manufacturing Engineering The Queen’s University of Belfast l EINEMANN OXFORD AMSTERDAM BOSTON LONDON NEW YORK PARIS SAN DlEGO SAN FRANCISCO SINGAPORE SYDNEY TOKYO Butterworth-Heinemann An imprint of Elsevier Science Linacre House. Jordan Hill, Oxford OX2 8DP 225 Wildwood Avenue, Woburn, MA 01801-2041 First published 1981 Second edition 1987 Reprinted with corrections 1990. 1992 Third edition 1998 Reprinted 1999.2001, 2002 Copyright 0 1987, 1998 R.J. Crawford. All rights reserved The right of R.J. Crawford to be identified as the author of this work has been asserted in accordance with the Copyright. Designs and Patents Act 1988 No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England WIT 4LP. Applications for the copyright holder’s written permission to reproduce any part of this publication should be addressed to the publishers. British Library Cataloguing in Publication Data Crawford, R.J. (Roy J.) Plastics engineering. 3rd ed. 1. Plastics I. Title 668.4 ISBN 0 7506 3764 1 Library of Congress Cataloguing in Publication Data Crawford, R.J. Plastics engineering/R.J. Crawford - 3rd ed. p. cm. Includes index. ISBN 0 7506 3764 1 (pbk). 1 Plastics. I Title TP1120 C74 97-36604 668.4 - dc21 CIP For information on all Butterworth-Heinemann publications visit our website at www.bh.com Typeset by Laser Words, Chennai, India Printed by St Edmundsbury Press Ltd, Bury St Edmunds, Suffolk Contents Preface to the Third Edition Preface to the Second Edition Preface to the First Edition Chapter 1 - General Properties of Plastics 1.1 Introduction 1.2 Polymeric Materials 1.3 Plastics Available to the Designer 1.3.1 Engineering Plastics 1.3.2 Thermosets 1.3.3 Composites 1.3.4 Structural Foam 1.3.5 Elastomers 1.3.6 Polymer Alloys 1.3.7 Liquid Crystal Polymers 1.4 Selection of Plastics 1.4.1 Mechanical Properties 1.4.2 Degradation 1.4.3 1.4.4 Special Properties 1.4.5 Processing 1.4.6 Costs Wear Resistance and Frictional Properties xi Xlll xv 1 1 2 6 6 7 8 9 9 11 12 18 18 26 28 30 35 37 vi Contents Chapter 2 - Mechanical Behaviour of Plastics 41 2.1 Introduction 2.2 Viscoelastic Behaviour of Plastics 2.3 Short-Term Testing of Plastics 2.4 Long-Term Testing of Plastics 2.5 2.6 Thermal Stresses and Strains 2.7 Multi-layer Mouldings 2.8 Design of Snap Fits 2.9 Design of Ribbed Sections 2.10 Stiffening Mechanisms in Other Moulding Situations 2.1 1 Mathematical Models of Viscoelastic Behaviour 2.12 Intermittent Loading Design Methods for Plastics using Deformation Data 2.12.1 Superposition Principle 2.12.2 Empirical Approach 2.13 Dynamic Loading of Plastics 2.14 Time-Temperature Superposition 2.15 Fracture Behaviour of Unreinforced Plastics 2.16 The Concept of Stress Concentration 2.17 Energy Approach to Fracture 2.18 Stress Intensity Factor Approach to Fracture 2.19 General Fracture Behaviour of Plastics 2.20 Creep Failure of Plastics 2.20.1 2.20.2 Crazing in Plastics 2.21.1 Effect of Cyclic Frequency 2.21.2 Effect of Waveform 2.21.3 Effect of Testing Control Mode 2.2 1.4 Effect of Mean Stress 2.21.5 Effect of Stress System 2.21.6 Fracture Mechanics Approach to Fatigue 2.22 Impact Behaviour of Plastics 2.22.1 Effect of Stress Concentrations 2.22.2 Effect of Temperature 2.22.3 Miscellaneous Factors Affecting Impact 2.22.4 Impact Test Methods 2.22.5 Fracture Mechanics Approach to Impact Fracture Mechanics Approach to Creep Fracture 2.21 Fatigue of Plastics Chapter 3 - Mechanical Behaviour of Composites 3.1 3.2 Types of Reinforcement Deformation Behaviour of Reinforced Plastics 41 42 43 45 48 61 66 71 74 81 84 95 95 103 110 116 119 121 121 127 131 134 136 137 138 140 142 142 143 145 145 147 148 150 152 152 154 168 168 168 Contents 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 Types of Matrix Forms of Fibre Reinforcement in Composites Analysis of Continuous Fibre Composites Deformation Behaviour of a Single Ply or Lamina Summary of Approach to Analysis of Unidirectional Composites General Deformation Behaviour of a Single Ply Deformation Behaviour of Laminates Summary of Steps to Predict Stiffness of Symmetric Laminates General Deformation Behaviour of Laminates Analysis of Multi-layer Isotropic Materials Analysis of Non-symmetric Laminates Analysis of Short Fibre Composites Creep Behaviour of Fibre Reinforced Plastics Strength of Fibre Composites 3.16.1 Strength of Single Plies 3.16.2 Strength of Laminates 3.17 Fatigue Behaviour of Reinforced Plastics 3.18 Impact Behaviour of Reinforced Plastics Chapter 4 - Processing of Plastics 4.1 Introduction 4.2 Extrusion 4.2.1 4.2.2 Mechanism of Flow 4.2.3 4.2.4 ExtruderDie Characteristics 4.2.5 Other Die Geometries 4.2.6 4.2.7 4.3 Injection Moulding 4.3.1 Introduction 4.3.2 Details of the Process 4.3.3 Moulds 4.3.4 Structural Foam Injection Moulding 4.3.5 Sandwich Moulding 4.3.6 Gas Injection Moulding 4.3.7 4.3.8 Reaction Injection Moulding General Features of Single Screw Extrusion Analysis of Flow in Extruder General Features of Twin Screw Extruders Processing Methods Based on the Extruder Shear Controlled Orientation in Injection Moulding (SCORIM) vii 170 171 172 182 188 195 202 206 208 218 223 226 232 232 234 236 238 240 245 245 246 246 25 1 252 257 259 262 264 278 278 279 285 297 298 299 30 1 302 Vlll Contents 4.3.9 Injection Blow Moulding 4.3.10 Injection Moulding of Thermosetting Materials 4.4 Thermoforming 4.4.1 Analysis of Thermoforming 4.5 Calendering 4.5.1 Analysis of Calendering 4.6 Rotational Moulding 4.6.1 Slush Moulding 4.7 Compression Moulding 4.8 Transfer Moulding 4.9 Processing Reinforced Thermoplastics 4.10 Processing Reinforced Thermosets 4.10.1 Manual Processing Methods 4.10.2 Semi-Automatic Processing Methods 4.10.3 Automatic Processes Chapter 5 - Analysis of polymer melt flow 5.1 Introduction 5.2 5.3 5.4 5.5 5.6 5.7 5.8 Residence and Relaxation Times 5.9 Temperature Rise in Die 5.10 Experimental Methods Used to Obtain Flow Data 5.11 Analysis of Flow in Some Processing Operations 5.12 Analysis of Heat 'lkansfer during Polymer Processing 5.13 Calculation of Clamping force General Behaviour of Polymer Melts Isothermal Flow in Channels: Newtonian Fluids Rheological Models for Polymer Melt Flow Isothermal Flow in Channels: Non-Newtonian Fluids Isothermal Flow in Non-Uniform Channels Elastic Behaviour of Polymer Melts Appendix A - Structure of Plastics A.l Structure of Long Molecules A.2 A.3 Arrangement of Molecular Chains Conformation of the Molecular Chain Appendix B - Solution of Differential Equations Appendix C - Stredstrain Relationships 303 304 306 309 313 315 318 323 323 326 327 328 330 332 337 343 343 344 346 35 1 354 357 363 367 368 369 375 39 1 40 1 413 413 415 420 425 426 Appendix D - Stresses in Cylindrical Shapes 429 Contents ix Appendix E - Introduction to Matrix Algebra E.1 Matrix definitions E.2 Matrix multiplication E.3 Matrix addition and subtraction E.4 Inversion of a matrix E.5 Symmetric matrix Appendix F - Abbreviations for some Common Polymers Solutions to Questions 43 1 43 1 432 432 433 433 434 435 Index 50 1 [...]... 45D 40D to 63D 60 to 70 43 to62 8 to 20 30 to 55 21 to 45 25 to 45 F F PIF E 0.97- 1. 34 -50 -13 0 PIG E F G 1. 11- 1. 21 -40 -13 0 E E G E 1. 17 -1. 25 -65- 13 0 E F P Polyurethane Polyester Styrenic PIE 0.93 -1. 0 -30- 12 0 Polyamide PIE PIE E 1. 0- 1. 12 -65 -13 0 (d) Thermosetting Plastics Aminos There are two basic types of amino plastics - urea formaldehyde and melamine formaldehyde They are hard, rigid materials... modulus MN/mz Specific gravity Relative thickness at equivalent rigidity Relative weight at equivalent rigidity 1. 4 1. 2 0.905 0.72 4.4 1. 24 2.5 1. 00 6.7 1. 12 3.5 0.90 2.3 7.9 0.650 0.6 41 70 2.7 207 7.83 1 1.05 0.68 0. 81 0.59 0.74 0.85 0.56 0.27 0 .19 1 0.84 0.94 0.90 0.74 0.73 0. 61 0.40 0. 81 1.65 manner and have sufficient flexibility to allow the material to undergo very large deformations In the green... (nylon) There are several different types of nylon (e.g nylon 6, nylon 66, nylon 11 ) but as a family their characteristics of strength, stiffness and toughness have earned them a reputation as engineering plastics Table 1. 3 compares the relative merits of light metal alloys and nylon 14 General Properties of Plastics Table 1. 3 Comparison between die casting alloys and nylons Points for comparison Die... advantages of plastics can be realised In the following sections most of the common plastics will be described briefly to give an idea of their range of properties and applications However, before going on to this it is worthwhile considering briefly several of the special categories into which plastics are divided 13 .1 Engineering P a t c lsis Many thermoplastics are now accepted as engineering materials... Typical performance data for foamed polypropylene relative to other materials is given in Table 1. 1 1. 3.5 Elastomers Conventional rubbers are members of the polymer family in that they consist of long chain-like molecules These chains are coiled and twisted in a random 10 General Properties of Plastics Table 1. 1 Comparison of structural foams based on various grades of polypropylene with some traditional... The olefinic type of TPR is the latest development and is different in that it consists of fine rubber particles in a thermoplastic matrix as shown in Fig 1. 1 11 General Properties of Plastics Rubber particles Tkrmoplastic matrix Ipolypmpylenc~ Fig 1. 1 npical structure of olefinic TF'R The matrix is usually polypropylene and it is this which melts during processing to permit shaping of the material The... engineering thermoplastics such as polyamides, polycarbonates, PPO, PET, PBT or acetal, nor by the considerably more expensive products such as polysulphone, polyethersulphone and PEEK 1. 33 Composites One of the key factors which make plastics attractive for engineering applications is the possibility of property enhancement through fibre reinforcement Composites produced in this way have enabled plastics. .. the questions R.J Crawford CHAPTER 1 - General Properties of Plastics 1. 1 Introduction It would be difficult to imagine our modem world without plastics Today they are an integral part of everyone’s lifestyle with applications varying f o rm commonplace domestic articles to sophisticated scientific and medical instruments Nowadays designers and engineers readily hun to plastics because they offer combinations... In this book no prior knowledge of plastics is assumed Chapter 1 provides a brief introduction to the structure of plastics and it provides an insight to the way in which their unique structure affects their performance There is a resume of the main types of plastics which are available Chapter 2 deals with the mechanical properties of unreinforced and reinforced plastics under the general heading... polyphenylene oxide, polysulphone, PVC, polyester (PET and PBT) and acrylic Barrier properties are improved by using plastics such as ethylene vinyl alchol (EVA) Some modern plastic alloys and their main characteristics are given in Table 1. 2 General Properties of Plastics 12 Table 1. 2 vpical plastic alloys Alloy PVClacrylic PVC/ABS Polycarbonate/ABS ABSPolysulphone Polyphenylene oxide/HIPS SAN/olefin . 45 48 61 66 71 74 81 84 95 95 10 3 11 0 11 6 11 9 12 1 12 1 12 7 13 1 13 4 13 6 13 7 13 8 14 0 14 2 14 2 14 3 14 5 14 5 14 7 14 8 15 0 15 2 15 2 15 4 16 8 16 8 16 8 Contents 3.3 3.4. Chapter 1 - General Properties of Plastics 1. 1 Introduction 1. 2 Polymeric Materials 1. 3 Plastics Available to the Designer 1. 3 .1 Engineering Plastics 1. 3.2 Thermosets 1. 3.3 Composites 1. 3.4. Avenue, Woburn, MA 018 01- 20 41 First published 19 81 Second edition 19 87 Reprinted with corrections 19 90. 19 92 Third edition 19 98 Reprinted 19 99.20 01, 2002 Copyright 0 19 87, 19 98 R.J. Crawford.