Table Of ContentORGANIC POLYMER CHEMISTRY
ORGANIC
POLYMER CHEMISTRY
AN INTRODUCTION TO THE ORGANIC CHEMISTRY
OF ADHESIVES, FIBRES, PAINTS, PLASTICS AND
RUBBERS
Second edition
K. J. SAUNDERS
Department of Applied Chemical and Biological Sciences
Ryerson Poly technical Institute, Toronto
LONDON NEW YORK
CHAPMAN AND HALL
First published in 1973 by
Chapman and Hall Ltd
11 New Fetter Lane, London EC4P 4EE
Second edition 1988
Published in the USA by
Chapman and Hall
29 West 35th Street, New York, NY 10001
© 1973, 1988 K. J. Saunders
Softcover reprint of the hardcover 2nd edition 1988
J. W. Arrowsmith Ltd. Bristol
ISBN -13:978-94-0 10-7031-7
All rights re~erved. No part of this book may be reprinted, or reproduced
or utilized in any form or by any electronic, mechanical or other means,
now known 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
Saunders, K. J. (Keith John)
Organic polymer chemistry: an introduction
to the organic chemistry of adhesives, fibres,
paints, plastics and rubbers.-2nd ed.
1. Polymers and polymerization
I. Title
547.7 QD381
ISBN-I3:978-94-010-7031-7 e-ISBN-13:978-94-009-1195-6
DOl: 10.1007/978-94-009-1195-6
Library of Congress Cataloging in Publication Data
Saunders, K. J. (Keith J.), 1931-
Organic polymer chemistry.
Includes index.
1. Polymers and polymerization. 2. Plastics.
I. Title.
TP1140.S32 1988 668.9 87-31974
ISBN-13:978-94-010-7031-7
This book is dedicated with gratitude to
my parents, Leonard and Marjorie Saunders,
for their sacrifices in earlier years and to
my wife, Jeannette,for her steadfast encouragement
in recent times.
CONTENTS
Preface page IX
1. Basic concepts
2. Polyolefins 46
3. Polystyrene and styrene copolymers 76
4. Poly(vinyl chloride) and related polymers 90
5. Poly(vinyl acetate) and related polymers 113
6. Acrylic polymers 125
7. Fluoropolymers 149
8. Miscellaneous vinyl polymers 167
9. Aliphatic polyethers 171
10. Polyamides and polyimides 191
11. Polyesters 224
12. Other aromatic polymers containing p-phenylene groups 265
13. Cellulose and related polymers 286
14. Phenol-formaldehyde polymers 316
15. Aminopolymers 341
16. Polyurethanes 358
17. Silicones 388
18. Epoxies 412
19. Polysulphides 436
20. Polydienes 447
Index 492
PREFACE
This book deals with the organic chemistry of polymers which find tech
nological use as adhesives, fibres, paints, plastics and rubbers. For the most
part, only polymers which are of commercial significance are considered and
the primary aim of the book is to relate theoretical aspects to industrial
practice. The book is mainly intended for use by students in technical
institutions and universities who are specializing in polymer science and by
graduates who require an introduction to this field. There are available
several books dealing with the physical chemistry of polymers but the organic
chemistry of polymers has not received so much attention. In recognition of
this situation and because the two aspects of polymer chemistry are often
taught separately, this book deals specifically with organic chemistry and
topics of physical chemistry have been omitted. Also, in this way the book has
been kept to a reasonable size. This is not to say that integration of the two
areas of polymer science is undesirable; on the contrary, it is important that
the inter-relationship should be appreciated.
I was gratified by the favourable comments prompted by the first edition of
the book and I have therefore retained the same organization in this second
edition. Nevertheless, the book has been extensively revised to reflect the
developments which have taken place. The most noticeable features of the
period since the publication of the first edition have been the continued
dominance of the same bulk commodity polymers and the appearance of
several new speciality engineering thermoplastics. I have aimed to be compre
hensive in scope and so both the well-established and the newer polymers are
dealt with in this edition.
KJ.S.
Department of Applied Chemical ana Biological Sciences,
Ryerson Poly technical Institute, Toronto, Ontario, Canada.
1
BASIC CONCEPTS
1.1 DEFINITIONS
A polymer may be defined as a large molecule comprised of repeating
structural units joined by covalent bonds. (The word is derived from the
Greek: poly - many, meros - part.) In this context, a large molecule is com
monly arbitrarily regarded either as one having a molecular weight of at least
1000 or as one containing 100 structural units or more. By a structural unit is
meant a relatively simple group of atoms joined by covalent bonds in a
specific spatial arrangement. Since covalent bonds also connect the structural
units to one another, polymers are distinguished from those solids and liquids
wherein repeating units (ions, atoms or molecules) are held together by ionic
bonds, metallic bonds, hydrogen bonds, dipole interactions or dispersion
forces.
The term macromolecule simply means a large molecule (Greek:
macros -large) and is often used synonymously with 'polymer'. Strictly
speaking, the terms are not equivalent since macromolecules, in principle,
need not be composed of repeating structural units though, in practice, they
generally are.
It may be noted that 'polymer' is often also used to refer to the massive
state. Then the term refers to a material whose molecules are polymers, i.e. a
polymeric material. Likewise, the term resin is sometimes used to refer to any
material whose molecules are polymers. Originally this term was restricted to
natural secretions, usually from coniferous trees, used mainly in surface
coatings; later, similar synthetic substances were included. Now the term is
generally used to indicate a precursor of a cross-linked polymeric material,
e.g. epoxy resin and novolak resin. (See later.)
1.2 SCOPE
A great variety of polymeric materials of many different types is to be found
throughout countless technological applications. For the purposes of this
book it is convenient to divide these materials according to whether they are
2 BASIC CONCEPTS
inorganic or organic and whether they are naturally occurring or synthetic.
Using this classification, the diverse nature and widespread application of
polymeric materials is illustrated by Fig. 1.1. This book is concerned solely
with technologically useful organic polymeric materials. These materials are
commonly classified as adhesives, fibres, paints, plastics and rubbers accord
ing to their use. Although these are all polymeric materials, they clearly
possess a great diversity of properties about which few generalizations can be
made. It is significant, however, that no low molecular weight organic
compounds are useful in the above applications. The physical properties of
an individual polymeric material are largely determined by molecular weight,
strength of intermolecular forces, regularity of polymer structure and flexi
bility of the polymer molecule.
POLYMERIC MATERIALS
I
I
1
INORGANIC ORGANIC
I I
I I I I
NATURAL SYNTHETIC NATURAL SYNTHETIC
I
I I
Clays Sands
I
.-----+-1 I
------'1
1 1 I I I
Brick Cemen~ Pottery Glass Fibres Adhesives Fibres Pain~s Plas~ics Rubbers
Polysaccharides Pro~eins Polyisoprene
I
1 I
I I I I
Adhesives Fibres Adhesives Fibres Rubber
Fig. 1.1 Some applications of polymeric materials.
1.3 RISE OF THE CONCEPT OF POLYMERS
Nowadays the concept of polymers (or, simply, big molecules) is easy to
accept but this has not always been the case. The rise of the concept is of
interest and a brief historical review is given below.
By the 1850s the existence of atoms and molecules was accepted but mainly
in respect of simple inorganic compounds. The application of these ideas to
more complex organic materials was not understood so clearly. At least, by
this time the notion that organic compounds all contained a mysterious 'vital
force' derived from living things had been finally abandoned as more and
more organic compounds were synthesized in the laboratory.
RISE OF THE CONCEPT OF POLYMERS 3
In 1858 Kekule suggested that organic molecules were somewhat larger
than the simple inorganic molecules and consisted of atoms linked in chains
by bonds. This led to the realization that the order in which atoms are
arranged in the molecule is significant, i.e. the meaning of 'structure' was
appreciated. These ideas, aided by improving methods of elemental analysis,
resulted in the elucidation of the structure of many simple organic com
pounds such as acetic acid and alcohol. However, virtually nothing was
deduced about the structure of more complex organic materials such as
rubber, cellulose and silk. All that was clear was that these materials had
elemental analyses which were quite similar to those of the simple com
pounds whose structures were known.
The first significant information came in 1861 when Graham found that
solutions of such natural materials as albumin, gelatin and glue diffused
through a parchment membrane at a very slow rate. Materials of this kind
were called colloids (Greek: kolla-glue). In contrast, solutions of materials
like sugar and salts diffused readily; these substances were called crystalloids
since they were generally crystalline. The reason for this difference was not
clear, but it was generally supposed that the colloid solute particles were
rather large and therefore their passage through the membrane was hindered.
There were a few tentative suggestions that the colloids had high molecular
weights so that a solute particle was large simply because it comprised one
large molecule. However, this view was not at all acceptable to most scientists
of the day. At this time the current practices of organic chemistry demanded
the preparation of crystalline compounds of great purity with exact elemental
analyses and sharp melting points. It was generally felt that if the colloids
were 'cleaned up' they would crystallize and reveal themselves as 'normal' low
molecular weight compounds. This view was apparently reinforced by the
fact that many inorganic materials of low molecular weight can be prepared
so that they behave as colloids, e.g. colloidal arsenious sulphide, gold and
silver chloride. It was held, quite rightly, that in these cases the colloidal
particles are aggregates of smaller particles held together by secondary
valency forces of some kind. (Incidentally, the physically associated groups
were frequently called 'polymers' in the literature.) This view was very much
in keeping with the great emphasis which was being placed on van der Waals
forces in the 1890s and early 1900s. By analogy, the organic colloids were
assumed to be molecular aggregates or micelles, a concept still to be found in
the literature of the 1940s.
The first worker to take a clearly opposite view was Staudinger in
Germany in a paper of 1920. He maintained that the colloidal properties of
organic materials are due simply to the large size of the individual molecules
and that such macromolecules contain only primary valency bonds.
Staudinger's initial evidence was mainly negative. Firstly, he demonstrated
that the organic materials retain their colloidal properties in all solvents in
4 BASIC CONCEPTS
which they dissolve. This is in contrast to the inorganic association colloids
which often lose their colloidal characteristics on change of solvent. Secondly,
he showed that, contrary to then current expectations, chemical modification
does not destroy the colloidal properties of the organic materials. At that time
it was commonly held that natural rubber was a cyclic material composed of
isoprene residues linked in rings of various sizes as, for example, in the
following structure:
Such molecules were then supposed to aggregate by virtue of secondary
valency forces arising from the presence of double bonds. (Incidentally, the
cyclic structure was held to account for the fact that no end-groups could be
detected.) However, Staudinger showed that the hydrogenation of natural
rubber produces a saturated material which still exhibits colloidal properties.
Thus he demonstrated that secondary forces originating from the unsatu
ration of natural rubber are unlikely to be responsible for colloidal behav
iour. Staudinger proposed the long chain structures, which are accepted
today, for several polymers. Additional support for the existence of macro
molecules came with the development of methods of molecular weight deter
mination. Until this time, only cryoscopic methods were available and these
were inadequate for the very high molecular weights involved; also, it was
commonly held that the laws which hold for ordinary solutions were not
applicable to colloidal solutions.
Thus by about 1930 the concept of polymers was firmly established even if
not universally accepted. The macromolecular viewpoint was finally secured
largely by the work of Carothers in the USA. This work was begun in 1929
and had as its objectives, clearly stated at the outset, the preparation of
polymers of definite structure through the use of established reactions of
organic chemistry and the elucidation of the relationship between structure
and properties of polymers. These researches were brilliantly successful and
finally dispelled the mysticism surrounding this field of chemistry.
One outstanding result of Carothers' work was the commercial develop
ment of nylon. Nylon stockings came on the market in 1940, when polymers,
in terms of popular acceptance, might be said to have arrived. The theor
etical, practical and economic foundations had been laid and since this date
progress has been phenomenal.
