Dietrich Braun

Simple Methods forIdentification of Plastics

5th Edition

BraunSimple Methods for Identifi cation of Plastics

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Dietrich Braun

Hanser Publishers, Munich Hanser Publications, Cincinnati

5th Edition

Simple Methods for Identifi cation of Plastics

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The Author:Prof. Dr. Dr. h. c. Dietrich Braun, Jakob-Jung-Straße 56, 64291 Darmstadt, GermanyTechnische Universität DarmstadtErnst Berl Institut für Technische und Makromolekulare Chemie

Distributed in North and South America by:Hanser Publications6915 Valley Avenue, Cincinnati, Ohio 45244-3029, USAFax: (513) 527-8801Phone: (513) 527-8977www.hanserpublications.com

Distributed in all other countries byCarl Hanser VerlagPostfach 86 04 20, 81631 München, GermanyFax: +49 (89) 98 48 09www.hanser.de

The use of general descriptive names, trademarks, etc., in this publication, even if the former are not especially identifi ed, 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 authors 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

Braun, Dietrich. [Erkennen von Kunststoff en. English] Simple methods for identifi cation of plastics / Dietrich Braun. - - 5th edition. pages cm ISBN 978-1-56990-526-5 (hardcover) - - ISBN 978-1-56990-542-5 (e-book) 1. Plastics--Analysis. I. Title. TP1140.B7213 2010 668.4’197- -dc23 2012045818

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ISBN 978-1-56990-526-5E-Book-ISBN 978-1-56990-542-5

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.

© 2013 Carl Hanser Verlag MunichProduction Management: Steff en JörgCoverconcept: Marc Müller-Bremer, www.rebranding.de, MünchenCoverdesign: Stephan RönigkTypeset by Kösel, Krugzell, GermanyPrinted and bound by Edwards Brothers, Inc.Printed in the USA

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Preface

Processors and users of plastics o� en, for many diff erent reasons, have to determine the chemical nature of a plastics sample. In contrast to plastics producers, however, they lack the specially equipped laboratories and the analytically trained staff for this purpose.

The complete identifi cation of a high-molecular weight organic material is a rather complicated and o� en expensive problem. For many practical needs it is o� en suffi cient to determine to which class of plastics an unknown sample belongs, for example, to fi nd out whether the material is a polyolefi n or a polyamide. To answer such a question, one usually only needs to use simple methods that do not require special chemical expertise.

In this book, now in its fi � h edition, the author has compiled a selection of proven procedures which, based on his own experience, will enable the technician, the engineer, and also the technical customer service represen-tative to identify an unknown plastic, e. g., for purposes of quality control or plastics recycling. All described procedures were carried out by the author as well as by students in courses at the German Plastics Institute. Addi-tional experience with these procedures was thus obtained and included in the book. The author welcomes any other comments and suggestions for additions by readers and users of this book.

Clearly one should not expect to obtain sophisticated information from these simple methods. In most cases, one has to be satisfi ed with the iden-tifi cation of the plastic material, whereas the analysis of sometimes very small amounts of fi llers, plasticizers, stabilizers, or other additives is only possible through the use of more advanced physical and chemical methods.

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VI Preface

Similarly, it is not possible with simple methods to identify with certainty such combinations as copolymers and polymer blends. In such cases more sophisticated methods of analysis are required.

As this book has also been found useful by collectors of historical plastics articles, professional conservators, restorers, and students of conservation sciences, in this new edition a small chapter on identifi cation of frequently used natural resins and some other early plastics has been included.

The good reception that previous English, German, Spanish, and French editions of this book have received from users and from reviewers in vari-ous plastics journals and magazines shows that in spite of all the modern analytical methods and advances in instrumental analysis, there is still a need for simple methods for the identifi cation of plastics. The analytical procedures described in this book do not require special chemical knowl-edge but they do require skills in carrying out simple operations. It is most important to remember to be careful in handling chemicals, solvents, and open fl ames; other precautions will be pointed out in the pertinent sections. The necessary equipment is listed in the Appendix. With most experiments it is recommended that parallel experiments with known materials are also carried out (a Plastics ID Kit is available through the Society of Plastics Engineers).

It is hoped that this edition fi lls the gap between the extensive plastics analysis volumes covering various methods in great detail and the tabular compilations of selected samples. Naturally, this entails a compromise between investing in a greater experimental eff ort or being satisfi ed with the more limited information that can be obtained from simple qualitative analytical methods.

The development and testing of the methods described in this book were part of the research programs at the German Plastics Institute and the author is grateful for some fi nancial support from German research organi-zations. The author also thanks the various people who collaborated on this project, especially Dr. R. Disselhoff , Dr. H. Pasch, and Dr. E. Richter and also Ms. Ch. Hock who obtained the IR-spectra. As in previous editions, the author thanks the Carl Hanser Verlag for good collaboration and for taking the author’s wishes into consideration.

Darmstadt, March 2013 Dietrich Braun

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Contents

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V

1 Plastics and Their Characteristics . . . . . . . . . . . . . . . . . . . . . . . . 1

2 General Introduction to the Analysis of Plastics . . . . . . . . . . 152.1 Analytical Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.2 Sample Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3 Screening Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193.1 Solubility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.2 Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.3 Behavior on Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

3.3.1 Pyrolysis Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

3.3.2 Flame Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

3.3.3 Melting Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

4 Testing for Heteroatoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

5 Analytical Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435.1 Analysis by Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

6 Specifi c Identifi cation Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 496.1 General Identifi cation Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

6.1.1 Liebermann-Storch-Morawski Reaction . . . . . . . . . . . . . . . . . . . 49

6.1.2 Color Reaction with p-Dimethylaminobenzaldehyde . . . . . . . . . 49

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VIII Contents

6.1.3 The Gibbs Indophenol Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

6.1.4 Formaldehyde Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

6.2 Specifi c Plastics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

6.2.1 Polyolefi ns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

6.2.2 Polystyrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

6.2.3 Polymethyl Methacrylate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

6.2.4 Polyacrylonitrile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

6.2.5 Polyvinyl Acetate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

6.2.6 Polyvinyl Alcohol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

6.2.7 Polymers Containing Chlorine . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

6.2.8 Polyoxymethylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

6.2.9 Polycarbonates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

6.2.10 Polyamides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

6.2.11 Polyurethanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

6.2.12 Phenolics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

6.2.13 Aminoplastics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

6.2.14 Epoxy Resins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

6.2.15 Polyesters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

6.2.16 Cellulose Derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

6.2.17 Silicones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

6.2.18 Rubberlike Plastics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

6.2.19 High Temperature-Resistant (HT) Thermoplastics . . . . . . . . . . . 66

6.2.20 Fibers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

6.3 Polymer Blends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

6.4 Detection of Metals in Polyvinyl Chloride (PVC) . . . . . . . . . . . . . . . . . . . 72

7 Identifi cation of Historic Plastic Objects . . . . . . . . . . . . . . . . . 757.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

7.1.1 Dating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

7.1.2 Visual Appearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

7.1.2.1 Transparency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

7.1.2.2 Hardness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

7.1.2.3 Odor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

7.1.2.4 Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

7.1.2.5 How to Distinguish Between Thermoplastics and Duroplastics 78

7.1.2.6 Material Behavior on Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

7.2 A Few Simple Chemical Tests to Identify Early Plastic Articles . . . . . . 81

7.2.1 Protein Derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

7.2.2 Natural Resins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

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IX Contents

8 Advanced Analytical Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . 858.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

8.2 Infrared Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

8.3 IR-Spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

9 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1039.1 Plastics Identifi cation Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

9.2 Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

9.2.1 Acids and Bases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

9.2.2 Inorganic Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

9.2.3 Organic Solvents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

9.2.4 Organic Reagents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

9.2.5 Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

9.3 Laboratory Aids and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

9.3.1 Basic Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

9.3.2 Optional Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

9.4 Selected Polymer Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

10 Literature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

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Plastics are high molecular weight (macromolecular or polymeric) organic substances that have usually been synthesized from low molecular weight compounds. They may also have been obtained by chemical modifi cation of high molecular weight natural materials (especially cellulose). The raw materials are most o� en petroleum, natural gas, and coal. They can be reacted with air, water, or sodium chloride to prepare reactive monomers. The most important industrial synthetic processes for the preparation of plastics from monomers may be classifi ed according to the mechanism of the formation reaction of the polymer, such as polymerization and conden-sation reactions. Since several chemically identical or similar plastics can be prepared in several diff erent ways and from diff erent raw materials, this classifi cation has little meaning for the analysis of unknown plastics sam-ples. On the other hand, in addition to chemical investigations, the appear-ance of a plastic as well as its behavior on heating yields useful information for its identifi cation.

There are physical interactions between the individual macromolecules that constitute a plastic material, just as there are between the molecules of a low molecular weight compound. These physical interactions are respon-sible for cohesion and related properties such as strength, hardness, and so� ening behavior. Plastics that consist of linear threadlike molecules ( several hundred nanometers (nm) long and a few tenths of a nanometer in diameter) (1 nm = 10–9 m = 10 Å = 10–6 mm), i. e., of macromolecules, that are not strongly crosslinked can usually be so� ened on heating. In many cases they melt. Thus, when a polymeric material is heated above a certain

1 Plastics and Their Characteristics

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2 1 Plastics and Their Characteristics

temperature, the macromolecules which are more or less oriented with respect to each other at low temperatures can glide past each other to form a melt of relatively high viscosity. Depending on the degree of order of the macromolecule in the solid state, it is possible to distinguish between partly crystalline and (mostly disordered) amorphous plastics (see Figure 1.1). This degree of order also has an eff ect on the behavior of the plastic on heat-ing and on its solubility.

Plastics that so� en on heating and start to fl ow are called thermoplastics. On cooling, such plastics become solid again. This process can be repeated many times. There are several exceptions, as when the chemical stability (expressed in terms of the temperature at which chemical decomposition starts) is lower than the cohesion between the macromolecules due to inter-actions between the chains, in which case, on heating, the plastic under-goes chemical changes before it reaches its so� ening or melting point.

THERMOSETS THERMOPLASTICS

Three-Dimensional

Network Melecules

amorphous amorphous partially crystalline

Individual Chain Molecules

FIGURE 1.1  Schematic representation of the structure of plastics, showing the three

major types of macromolecular arrangements. Approximately 1 000 000 times actual

size and greatly simplifi ed. (Crystallites can also occur as the result of chain folding.)

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31 Plastics and Their Characteristics

A further indication, with few exceptions, that macromolecules are linear or branched is their solubility in many liquids, such as organic solvents. This process also reduces the interaction between the macromolecules; solvent molecules insert themselves between the polymer chains.

In contrast to thermoplastic materials, there are the so-called thermoset-ting materials. These, a� er processing into their fi nal state, are crosslinked macromolecules that can neither melt nor dissolve. For such products one generally starts with liquid or soluble raw materials of a rather low molec-ular weight. These may be crosslinked by heating with or without pressure or through chemical reactions with additives and concurrent molding con-ditions. The results are crosslinked ( hardened) high molecular weight mate-rials in three-dimensional networks. These giant molecules can be broken down into smaller and therefore meltable and soluble fragments only by chemical destruction of the crosslinks. This may occur at rather high tem-peratures or with certain chemical reagents. Thermosets o� en contain fi llers that may strongly infl uence the appearance and properties of the products.

Finally, we may distinguish the elastomers by their physical appearance which is a rubberlike elastic material that usually consists of relatively weakly crosslinked macromolecules. Crosslinkages of natural or synthetic rubber are formed during the molding or vulcanization process. Because of their crosslinked nature, elastomers do not melt on heating until just below their decomposition temperature. In this sense they behave diff erently from many other elastic thermoplastic materials such as plasticized polyvinyl chloride (PVC). In contrast to the chemically crosslinked elastomers (rub-ber), e. g., by sulfur or peroxides, network formation in the so-called ther-moplastic elastomers (TPE) occurs through physical interactions between the macromolecules. On heating, the physical interaction forces between the chain molecules decrease, so that these polymers can be thermoplasti-cally shaped. On cooling, as the physical interaction between the molecules becomes stronger, the material again behaves like an elastomer.

Table 1.1 lists the most important characteristics of these three groups of polymeric materials. In addition to elasticity, behavior on heating, density, and solubility can be used to diff erentiate between these materials. How-ever, it should be kept in mind that fi llers, pigments, or reinforcing agents,

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