Myer Ezrin

Plastics Failure GuideCause and Prevention

2nd Edition

Ezrin Plastics Failure Guide

Plastics Failure Guide

Myer Ezrin

Hanser Publishers, Munich Hanser Publications, Cincinnati

Cause and Prevention

2nd Edition

The Author:Dr. Myer Ezrin (retired)Institute of Materials Science, University of Connecticut, Sorrs, CT 06269-3136, USACurrent address: 43 Morgan Ridge, Longmeadow, MA 01106

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

Ezrin, Myer. Plastics failure guide : cause and prevention / Myer Ezrin. -- 2nd edition. pages cm ISBN 978-1-56990-449-7 (hardcover) -- ISBN (invalid) 978-3-446-42882-9 (e-book) 1. Plastics--Fracture. I. Title. TA455.P5E95 2013 620.1’9236--dc23 2013001575

Bibliografische Information Der Deutschen Bibliothek Die Deutsche Bibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografie; detaillierte bibliografische Daten sind im Internet über <http://dnb.d-nb.de> abrufbar.

ISBN 978-1-56990-449-7E-Book ISBN 978-3-446-42882-9

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.

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Preface to Second Edition

In the Plastics Failure Guide—Cause and Prevention—Second Edition, four factors of plastics technology provide an approach to solving predictable and unpredictable failures. They are Material, Design, Processing and Service Conditions. Prevention is treated as well. All chapters have “Lessons” at the end to emphasize the most important aspects of each chapter.

Beside fracture, which is the best known type of plastics failure, many other kinds of failure are covered, such as appearance change and warpage. Plastics failure may lead to time consuming and expensive product liability litigation that could end in bankruptcy. Chapters 1–6 cover various aspects of failure analysis along the lines of the four factors that are important in plastics failure indicated above, starting with Material. Testing, Quality Control and Legal are covered in Chapters 7, 8, and 9, respectively. Four product areas round out the first 13 chapters: Composites, Pipe, Medical, and Electrical/Electronics, respectively.

The first thirteen chapters have been expanded from the first edition. In addition, there are three new chapters which are Chapter 14, Adhesion Failure of Plastics; Chapter 15, Failure of Human Biopolymers; and Chapter 16, Environmental, Recycling, and Health Aspects of Plastics Failure.

Some adhesion failures were included in the first edition, but the new Chapter 14 brings a fuller treatment to the subject.

Failure of Human Biopolymers extends the treatment of synthetic polymer failure to human biopolymers, life’s natural polymers. There is a similarity in chemical composition and in susceptibility to failure by the same forces. For example, both polymer types are susceptible to failure by free radicals.

Chapter 16 brings a realization that some failures are due to recent changes in environmental, recycling, and health effects. Some of the new failures are for compositions that were considered desirable for as long as fifty years. An example is PVC phthalate plasticizers, such as DOP (dioctyl phthalate), which is banned in some products for children up to three years old. Much of the new failure types for plastics are due to recent environmental concerns, just as lead became unwelcome

VI Preface to Second Edition

and banned. Polycarbonate was the darling of unbreakable sterilized baby bottles for many years, but now is practically banned because of BPA (bisphenol A) monomer released with heat in sterilization.

There are big changes in what constitutes some failures. What used to be a great success technically and economically may be banned either officially or by popular demand for a concern that is no longer tolerated. Failure is failure, no matter how or why. “Read all about it.”

Longmeadow, Massachusetts January, 2013

Acknowledgements

■■ First Edition

The basis of this book is the experience and research in plastics failure gained during fifteen years at Springborn Laboratories, a plastics consulting company in Enfield, CT, and fourteen years at the University of Connecticut, Institute of Materi-als Science. Throughout those years, a great many and varied cases of failure were addressed or came to the author’s attention. W. Larsen, W. Tenero, and R. White, former Springborn associates, provided much useful information and perspective on the subject. R. Geoffroy, also a former Springborn colleague and now with Polymer Services Group, Somers, CT, has provided insightful, patient and extraordinarily helpful information and constructive criticism, without which the book would be less thorough.

Thanks also to L. V. Azaroff and A. T. DiBenedetto, the directors of the Institute of Materials Science during the last fourteen years, for allowing the author to pursue failure-related research and writing while fulfilling the primary responsibilities of directing a university-industry technology extension program.

Much insight into plastics failure was provided by the Polymer Science faculty and associates of the Institute, in particular J. Bell, D. Damon, T. Davidson, A. DiBenedetto, J. Groeger, S. Huang, J. Jancar, M. Mashikian, M. Shaw, and J. Tanaka. G. Lavigne has contributed greatly to analytical expertise for plastics failure analysis.

Checklists and procedures for systematic failure analysis are an important part of this text. Those of E. Stumpek, G. E. Plastics; R. Grove and B. Smith, Boeing Aircraft (for the U.S. Air Force); R. Hauser of Hauser Chemical Research, and C. Bauer of Carl Bauer Verbindunstechnik GMBH, Federal Republic of Germany, have been incorporated into the text.

Similarly, checklists and guidelines for plastics design have been borrowed from the book of S. Levy and J. H. DuBois (“Plastics Product Design Engineering Hand-book”) and from short course information of M. Blumenfeld. Information of J. O’Toole on design, material selection and plastics properties has been used from a

VIII Acknowledgements

comprehensive group of articles in “Modern Plastics Encyclopedia” 1984–85 and 1985–86. I. M. Spier is another resource person whose writings have been utilized in Chapter 3 on design. W. Tobin and G. Beall are consultants whose expert work in design and failure have been included in this book. The work of L. Broutman in plastics testing and failure analysis has also been quoted.

The book of Brostow and Corneliussen, “Failure of Plastics”, has been an important source of theoretical and basic information on many aspects of failure.

Chapter 9 on legal aspects of plastics failure uses considerable material from C. Witherell’s book, “How to Avoid Products Liability, Lawsuits and Damages”. Also in Chapter 9 a paper on product liability of T. Guida, Insurance Company of North America, has been quoted several times.

The “Gallery of Goofs” series, and other articles, in “Plastics Design Forum” have been a valuable resource for plastics failure case studies and other information. Some case studies have been included from D. Himmelfarb’s book, “A Guide to Product Failures and Accidents”. Other literature sources that have been useful are the journal Kunststoffe German Plastics, particularly for processing technology, and Encyclopedia of Materials Science and Engineering.

Several illustrations of pipe failures have been used which came from A. Lustiger’s Battelle report on gas pipe failures.

The people cited above are only some of the many whose published and unpub-lished material and suggestions have been incorporated into the book. Many others are acknowledged by reference to “private communication” or in other ways. To everyone who was a resource for “Plastics Failure Guide: Cause and Prevention”, thank you very much.

Finally, the author is indebted to Irene Gordon for her patient and careful prepara-tion of the manuscript.

IX Acknowledgements

■■ Second Edition

The author thanks the publisher, Hanser, for its approval of two new chapters, which break new ground in plastics failure—Failure of Human Biopolymers (15) and Environmental, Recycling, and Health Aspects of Plastics Failure (16). These have become active areas in plastics technology.

Special thanks to Paul Gramann of The Madison Group, Madison, WI, for his contri-bution of many cases in Chapters one to seven. The book is enriched by his material.

Thanks to two attorneys for agreeing to have their litigated failures presented in a technical paper—Darryl Yee and Laura Uddenberg. The author helped bring success-ful conclusions to their separate cases of plastics failure in water service. The cases are included in Sections 4.2.1.1.3 and 4.2.1.2.1.

Many of the failures in the book were first presented at the Annual Technical Conferences of the Society of Plastics Engineers (ANTEC-SPE) and are published in the Proceedings. The author’s papers on plastics analysis and plastics failure analysis are listed in Section 1.14. Most papers at ANTEC were given in sessions of the Failure Analysis and Prevention Special Interest Group.

Many solutions of plastics failure were made using instruments of the Uni-versity of Connecticut—micro-infrared spectroscopy, ATR (attenuated total reflectance spectroscopy), Raman Spectroscopy, SEM-EDX (scanning electron microscopy/-energy dispersive X-ray spectroscopy), XPS (X-ray photoelectron spectroscopy), GPC (gel permeation chromatography), thermal analysis methods (DSC, TGA, DMA), TD/GC/MS (thermal desorption/gas chromatography/mass spectroscopy), and melt flow rate. Another is our eyes, a powerful instrument for plastics failure analysis.

Special mention goes to TD/GC/MS, developed at UCONN for analysis of volatile and semi-volatile materials. The extraordinarily talented person behind the method is Gary Lavigne, who invented the TD device. Examples of its use in plastics failure are analysis of monomers, stabilizers, antioxidants, curing agents, stress-cracking agents and contaminants. A pyrolytic device (900C) for GC/MS, also an invention of his, was used in analysis for trace silicone polymer in recycled paper without inter-ference from Inorganic silicon compounds The paper won the 2002 Best Paper Award of the SPE Plastics Analysis Division; special thanks to Gary (Section 7.4.3.3.1).

A failed and degraded printed circuit board of a dishwasher was provided by Jonathan Ezrin (Section 13.3.4.2.1).

Special thanks to Nancy Borman, who expertly prepared and edited the manuscript.

The author expresses his appreciation to all who contributed to the book but may have been overlooked unintentionally.

Contents

Preface to Second Edition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VIIFirst Edition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VIISecond Edition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IX

1 A Preliminary Look at the Nature, Causes, and Consequences of Plastics Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Plastics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.3 Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.4 Rubbers and Elastomers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41.5 Natural Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41.6 Plastics in the Family of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.7 Common Features and Differences in Performance or Failure of all

Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.8 Unintentional Factors Affecting Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.9 Types and Causes of Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.9.1 When Failure is Not Really a Failure . . . . . . . . . . . . . . . . . . . . 111.10 The People Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131.11 The Consequences of Plastics Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141.12 Legal and Financial Aspects of Plastics Failure  . . . . . . . . . . . . . . . . . . . . . 15

1.12.1 Lessons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171.13 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171.14 Papers by Myer Ezrin and Coauthors on Plastics Failure Analysis,

Plastics Analysis , and Related Subjects . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191.14.1 Plastics Failure Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191.14.2 Plastics Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211.14.3 Electrical Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221.14.4 Solar Panel Encapsulant Discoloration . . . . . . . . . . . . . . . . . . 221.14.5 Plastics Recycling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

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2 Fundamental Materials Variables Affecting Processing and Product Performance or Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252.1 The Overall Picture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252.2 Polymer Composition  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

2.2.1 Major Categories of Plastics Composition . . . . . . . . . . . . . . . . 292.2.1.1 Thermoplastic and Thermosetting Plastics . . . . . . . . . . . . . . 292.2.1.2 Thermoplastic Elastomers  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312.2.2 Types of Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312.2.2.1 Addition Polymers Based on Vinyl Monomers . . . . . . . . . . . 312.2.2.2 Thermal and Photolytic Stability of Vinyl Addition

Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332.2.2.3 Thermal Analysis in the Study of Polymer Degradation . . . 362.2.2.4 Controlling Thermal Effects in Performance or Failure of

Plastics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372.2.2.5 Elastomeric Addition Polymers Based on Diene

Monomers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372.2.2.6 Condensation Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372.2.2.7 Other Polymer Types  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392.2.2.8 Homopolymers, Copolymers, Terpolymers, and Blends . . . 40

2.3 Composition—Intentional Additives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412.3.1 Types of Additives  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412.3.2 Failure Effects of Intentional Additives . . . . . . . . . . . . . . . . . . 412.3.2.1 Plasticizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422.3.2.1.1 Adhesion Failure of Vinyl Floor Tiles . . . . . . . . . . . . . . . . . . . . 422.3.2.1.2 Other Plasticizer-Related Failures . . . . . . . . . . . . . . . . . . . . . . . 422.3.2.2 Colorants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432.3.2.2.1 Staining of Clothes by Plastic Hangers  . . . . . . . . . . . . . . . . . . 432.3.2.2.2 Effect of Colorants on Notch Sensitivity . . . . . . . . . . . . . . . . . 442.3.2.2.3 Poor Mixing of Colorant in Water Filter Canister . . . . . . . . . 442.3.2.3 Flame Retardants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482.3.2.3.1 Omission of Flame Retardants . . . . . . . . . . . . . . . . . . . . . . . . . . 482.3.2.3.2 Effect on Mold and Part Dimensions . . . . . . . . . . . . . . . . . . . . 492.3.2.3.3 Effect on a Secondary Part of the Product  . . . . . . . . . . . . . . . 502.3.2.3.4 Effect of Frozen-In Stress on Molded Parts Causing Early

Failure in Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 502.3.2.4 Unanticipated Effect of Additive . . . . . . . . . . . . . . . . . . . . . . . . 502.3.2.4.1 Enhanced Crystallization Due to a Pigment . . . . . . . . . . . . . . 502.3.2.4.1.1 Shampoo Tube Screw Caps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 502.3.2.4.1.2 The Case of the Shrinking Polyethylene Milk Case . . . . . . . 512.3.2.5 Poor Dispersion of Additives—Antioxidant . . . . . . . . . . . . . . . 522.3.2.6 Volatility of Additives—Antioxidant . . . . . . . . . . . . . . . . . . . . . . 53

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2.4 Composition—Unintentional Additives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 542.4.1 Types of Unintentional Additives . . . . . . . . . . . . . . . . . . . . . . . 542.4.2 Failure Effects of Unintentional Additives . . . . . . . . . . . . . . . 542.4.2.1 Extraneous Dirt, Lint, and Other Contaminant Materials . 542.4.2.1.1 Contaminant from Previous Run in Extruder . . . . . . . . . . . . 552.4.2.2 Residual Monomer, Solvent, or Other Low Level

Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592.4.2.3 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602.4.2.3.1 Beneficial Effects of Water Absorbed from the Air . . . . . . . . 602.4.2.3.2 Hydrolysis of Condensation Type Plastics in Melt

Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602.4.2.3.3 Appearance Problem Due to Water in Melt Processing . . . 602.4.2.3.4 Voids Formed by Water in Melt Processing . . . . . . . . . . . . . . 612.4.2.3.5 Water Treeing of Extruded Polyolefin Electrical Power

Cables  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 612.4.2.3.6 Shrinkage and Expansion of Moldings . . . . . . . . . . . . . . . . . . 622.4.2.4 Compounding Process Aids in Additives Concentrates . . . 622.4.2.5 Additives in Formulation Ingredients to Improve their

Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 632.4.2.6 Ionic Impurities from Water in Service  . . . . . . . . . . . . . . . . . . 632.4.2.7 Ionic Impurities in Carbon Black  . . . . . . . . . . . . . . . . . . . . . . . 642.4.2.8 Trace Metal from Extruder Barrel and Screw Coating . . . . 642.4.2.9 Impurities in Intentional Additives or Processing

Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 642.5 Molecular Weight (MW) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 642.6 Intermolecular Order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

2.6.1 Crystallinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 692.6.2 Crosslinking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 722.6.3 Orientation Due to Processing . . . . . . . . . . . . . . . . . . . . . . . . . . 742.6.4 Degree of Fusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 762.6.5 Physical Aging  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

2.7 Combined Effect of Molecular Weight and Crystallinity . . . . . . . . . . . . . 772.8 Lessons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 782.9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

3 Failures Related to Design and Material Selection . . . . . . . . . . . . . . . . . . . . . . . 833.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 833.2 Basic and Practical Considerations in Design-Related Failures . . . . . . 83

3.2.1 The People Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 833.2.2 Declaring War on Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 853.2.3 To Test or Not to Test—or How Much is Enough? . . . . . . . . . . 86

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3.2.4 The Perfect Design and Product—Does It Exist? . . . . . . . . . . 883.2.5 The Prototype . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 883.2.6 Effect of Design on Processing . . . . . . . . . . . . . . . . . . . . . . . . . . 883.2.7 Design Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 893.2.8 The Most Common Mistakes in Design of Plastics . . . . . . . . 903.2.8.1 Creep  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903.2.8.2 Stress  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 923.2.8.3 Hostile Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 923.2.8.4 Shrinkage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 923.2.8.5 Color Variance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 923.2.8.6 Gate Marks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 923.2.8.7 Inadequate Draft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 933.2.8.8 Sink Marks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 933.2.8.9 Unanticipated Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 943.2.8.10 Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 943.2.9 Product Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 943.2.9.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 943.2.9.2 Design Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 953.2.9.3 Performance Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 953.2.10 Design for Service Life and Service Conditions . . . . . . . . . . 963.2.11 The Hazards of Simultaneous Service Factors . . . . . . . . . . . . 973.2.12 Brittle Fracture—A Balancing Act of Design and Material . 973.2.12.1 The Ductile to Brittle Transition . . . . . . . . . . . . . . . . . . . . . . . . 983.2.12.2 Molecular Weight (MW) and Brittle Fracture . . . . . . . . . . . 1003.2.13 Comparison of Plastics and Metals  . . . . . . . . . . . . . . . . . . . . . 1003.2.14 Crack Phenomena in Fracture . . . . . . . . . . . . . . . . . . . . . . . . . 1013.2.15 Failure by Fatigue  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1043.2.15.1 Fatigue Failure by Crack Propagation . . . . . . . . . . . . . . . . . . 1043.2.15.2 Failure by Softening Due to Hysteretic Heating . . . . . . . . . 1063.2.15.3 Effect of Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1083.2.16 Failure by Creep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1103.2.16.1 Fundamentals of Creep Behavior. . . . . . . . . . . . . . . . . . . . . . . 1103.2.16.2 Tests to Predict Creep Behavior . . . . . . . . . . . . . . . . . . . . . . . . 1113.2.16.3 A Case Study of Creep Failure  . . . . . . . . . . . . . . . . . . . . . . . . . 1123.2.16.4 Creep Failure of a Thermoset Polymer . . . . . . . . . . . . . . . . . . 1163.2.17 Failure by Impact  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1173.2.17.1 Design Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1173.2.17.1.1 Case Study of a Design Failure . . . . . . . . . . . . . . . . . . . . . . . . . 1193.2.17.2 Material Effects  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1203.2.17.3 Molding Effects  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1213.2.17.4 Molecular Weight (MW) Effects  . . . . . . . . . . . . . . . . . . . . . . . . 121