Aging and Stabilization of Polymers

373 Pages·1995·9.389 MB·English

by  Professor M. B. Neiman (auth.), Professor M. B. Neiman (eds.)

AGING AND STABILIZATION OF POLYMERS
STARENIE I STABILIZATSIYA POLIMEROV
CTAPEHME H CTABHflH3AilBH rrOflHMEPOB
AGING
AND STABILIZATION
OF POLYMERS
Edited by
M. B. Neiman
Translated from Russian
CONSULTANTS BUREAU
NEW YORK
1965
First Printing - March 1965
Second Printing - November 1968
ISBN-13: 978-1-4615-8551-0 e-ISBN-13: 978-1-4615-8549-7
DOl: 10.1007/978-1-4615-8549-7
The original Russian text was published for the Institute of Chemi
cal Physics of the Academy of Sciences of the USSR by Nauka, the
Academy of Sciences Press, in Moscow in 1964.
Library of Congress Catalog Card Number 64-23249
©1965 Consultants Bureau Enterprises, Inc.
Softcover reprint of the hardcover 1st edition 1965
227 West 17th St., New York, N. Y. 10011
All rights reserved
No part of this publication may be reproduced in any
form without written permission from the publisher
CONTENTS
Introduction: Significance and Prospects of the Stabilization
of Polymers and Articles Made from Them . . . . . 1
Chapter I. Mechanism of the Thermooxidative Destruction
and Stabilization of Polymers
1. Oxidation in the Gas and Liquid Phases. 4
2. Oxidation in the Solid Phase . 8
3. Oxidation in Polypropylene 10
4. Autoinhibition of the Oxidation of Polymers. 17
5. Critical Concentration of Antioxidants. 20
6. Initiation of Oxidation by Antioxidants. 24
7. Theory of Synergism. 29
8. Free Radicals as Stabilizers. 33
9. Boric Stabilizers 36
Bibliography 37
Chapter II. Stable Radicals of Inhibitors of Oxidative Pro
cesses
1. Phenoxyl Radicals ........ . 42
2. Stable Radicals of Naphthols. . . . . 49
3. Stable Radicals of Aromatic Amines. 51
4. Formation of Stable Radicals of Inhibitions During
Oxidation Processes 52
Bibliography . . . . . . . . . . . . . . . . . . . . . . . 54
Chapter III. Synthesis of Stabilizers for Polymer Materials
1. Photostabilizers 56
II. Antioxidants 65
Bibliography . . . . 84
Chapter IV. Aging and Stabilization of Polyolefins 94
I. Oxidative Destruction of Polyolefins. 95
v
vi ContentS
II. Stabilization of Polyolefins Against Oxidative Destruc-
tion. . . . . • • . . . . . . . . . . . . . . . . . . . . 103
III. Destruction of Polyolefins Under the Action of Light. 123
IV. Increasing the Light Stability of Polyolefins. 127
Bibliography . . . . . . . . . . . . . . . . . . . . . . 132
Chapter V. Aging and Stabilization of Polyformaldehyde
1. Thermal and Thermooxidative Destruction 137
2. Stabilization of Polyformaldehyde 146
3. Bonding of Formaldehyde by Polyamides . 147
4. Inhibition of the Process of Oxidation of Polyformal
dehyde by Inhibitors, Derivatives of Aromatic Amines
and Phenols, Phosphites, and Sulfur-Containing Com-
pounds . . . . . . . . . . . . . • . . . . • . . . . 152
5. Inhibition of the Oxidation of Polyformaldehyde by
Radical-Type Inhibitors . . . . . . . . • . . . . . 155
6. Consumption of Nitrogen Oxide Stable Radicals in the
Thermal Oxidation of Polyformaldehyde. . . . . . . . 157
Bibliography . . . . . . . . . . . . • . . . . • . . . . .. 159
Chapter VI. Aging and Stabilization of Polyvinyl Chloride and
Copolymers of Vinyl Chloride
I. Factors Determining the Mechanism and Rate of De-
composition of Polyvinyl Chloride .•.•..... 161
II. General Principles of the Stabilization of Polyvinyl
Chloride . . . • . • • . . . • . . . . . . . . . 176
III. Methods of Evaluating the Effectiveness of the
of the Action of Polyvinyl Chloride Stabilizers 192
IV. Stabilizers of Polyvinyl Chloride and Vinyl Chloride
Copolymers .. . . . . . . . . . . . . • . . 199
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . 216
Chapter VII. Aging and Stabilization of Polyamides
I. Thermal Aging of Polyamides . . . . . . . . 227
II. Thermal Oxidation of Polyamides ..... 238
III. Stabilization of polyamides Against Thermal
OxWatioo ............ . 247
IV. Photoaging of Polyamides • . . . 251
V. Photo stabilization of Polyamides 261
Bibliography . . . . . . . . . . . . . 265
Chapter VIII. Aging of Certain Condensation Polymers
I. Epoxide Resins. . . . . . . . . . • . . . . . . . 269
Contents vii
II. Phenol-Formaldehyde Resins 277
III. Polyarylates . 279
IV. Polycarbonate . . . . . . . . 285
Bibliography . . . . . . . . . . . 290
Chapter IX. Aging of Polymers with Inorganic Principal
Chains of the Molecules, Framed by Organic Groups • 292
Bibliography . • . . . . . . . . . . . . . . . . . • . . . . 311
Chapter X. Aging and Stabilization of Raw and Cured Rubbers 312
I. Thermal Oxidation of Raw Rubbers in the Presence of
Inhibitors. . . . . . . . . . . . . . . 313
II. Thermal Oxidation of Cured Rubbers . . . . . 322
III. Light Aging .•................ 323
IV. Aging of Raw Rubbers at High Temperatures . . 324
V. Corrosion Cracking of Cured Rubbers . . . . 330
VI. Aging of Polymers Under the Action of Ionizing Ra-
diations ...................... . 331
VII. Influence of Mechanical Stresses on the Aging of
Cured Rubbers . . . . . . . . . . . . . . . . . . . 335
Bibliography . . . . . . . . . . . . . . . . . • . . . • • 342
Chapter XI. Mechanochemical Processes in Highly Elastic
Polymers ...................... . 347
I. Cleavage of the Macromolecule . . . . • . . . . . . 348
II. Mechanochemical Phenomena in the Case of Repeated
Deformation of Highly Elastic Polymers . . . . . . . 350
III. Mechanochemical Phenomena in the Reprocessing of
Highly Elastic Polymers. 358
Bibliography . . . . . . • . . . . . . . . . . . . . . . . . 363
PREFACE
The need for a broad development of the production of polymer ma
terials has become evident. All these materials are subject to various
types of aging (destruction); hence, stabilizers which permit the stor
age, reprocessing, and use of polymer materials without any appreci
able change in their properties must be introduced into them. In recent
years, this problem of stabilizing polymers has attracted the attention
of many scientists and technologists, both in the USSR and abroad. The
scientific basis of the foreign studies will be found in a number of theo
retical premises, but chiefly the theory of chain reactions with un
branched chains.
In the Soviet Union, the concepts of Academician N. N. Semenov on
chain reactions with degenerate branches have become the starting point
of theoretical studies of the stabilization and destruction of polymers.
Soviet scientists have developed a theory of critical concentrations of
antioxidants and have shown that the processes of stabilization have a
very complex chemical character. The nature of the polymers them
selves greatly affects these processes and consequently, different stabil
izers are required for polymers of different structures. In addition, it
has been shown that the antioxidants used thus far can not only cause
chain termination, but can also initiate oxidation and give rise to de
generate branches.
All these studies were designed to create a scientific basis for the
purposeful selection of effective stabilizers. They were published, over
a period of years, in various journals, and by 1962 the need was felt for
a monograph on the aging and stabilization of polymers in which the re
sults of investigations of Soviet scientists would be systematically pre
sented, together with a critical survey of the studies of foreign re
searchers.
To speed up the publication of this monograph, a large group of
authors - specialists in polymer stabilization - was enlisted in its writ
ing. Some problems in which Soviet scientists have been interested to a
ix
x Preface
lesser degree, for example, thermal and photooxidative destruction,
have been treated in less detail in the monograph.
The introduction to the book was written by Academician V. A.
Kargin; the individual chapters were written by the following: Chapter I
by Professor M. B. Neiman; Chapter II by Candidate of Chemical Sci
ences A. L. Buchachenko; Chapter III by V. V. Mikhailovand 1. P.
Maslova; Chapter IV by Candidate of Chemical Sciences A. F. Lukovnikov
and E. N. Matveeva; Chapter V by Candidate of Chemical Sciences B. M.
Kovarskaya and Professor M. B. Neiman; Chapter VI by Professor A. A.
Berlin, Candidate of Chemical Sciences D. M. Yanovskii, and Candidate
of Chemical Sciences Z. V. Popova; Chapter VII by Candidate of Chemi
cal Sciences I. I. Levantovskaya; Chapter VIII by Candidate of Chemical
Sciences B. M. Kovarskaya; Chapter IX by Academician Professor K. A.
Andrianov; Chapter X by Professor A. S. Kuz'minskii; and Chapter XI
by Professor G. L. Slonimskii.
Professor M. B. Neiman
Introduction
SIGNIFICANCE AND PROSPECTS OF THE STABILIZATION
OF POLYMERS AND ARTICLES MADE FROM THEM
The problem of stabilization in the broad meaning of the word is
that of the conservation of the initial properties of polymer substances
and materials under the most varied influences: heat, radiation, me
chanical and chemical influences, primarily oxidation and hydrolysis,
and, finally, the influence of microorganisms. It is quite natural that
in this effort we come up against all the variety of chemical and struc
tural processes that occur during the breakdown of polymers, and we
arrive at the conclusion that stabilization cannot be accomplished for all
polymers by any single method. Hence, the particular problem that
forms the basis for polymer breakdown must be defined in each case.
The need for stabilizers arises already during reprocessing of the
polymers. It is known that the polymer substance should be converted
to the fluid state for reprocessing, and that the region of reprocessing
is the temperature region between the melting point and the temper
ature of thermal decomposition of the polymer. The broader this re
gion, and the greater the excess of the reprocessing temperature over
the melting point, the more easily and completely the process of re
processing will occur. Of course, it is more favorable to expand this
region by raising the decomposition temperature of the polymer by sta
bilization than by lowering the melting point, since lowering the melting
point also entails a reduction of the thermal stability of the material.
At present the overwhelming majority of polymers are reprocessed with
a stabilizer additive.
Stabilization also plays as important a role in applications of poly
mer materials, especially stabilization against the combined action of
light and oxygen and the effects of continuous mechanical action. Even
though the variety of mechanisms of polymer breakdown is great, chain
processes of oxidation and chain decomposition playa basic role. Hence
investigations related to the processes of the appearance of free radicals,
the elucidation of their role as initiators of various chain processes of
2 Introduction
oxidation and destruction, and, finally, a search for inhibitors of these
processes are the proper basic directions for studies in the field of
stabilization. These lines of study have been very fully explored, and
we shall therefore skip over them, and instead discuss less popular trends.
The action of inhibitors on free radicals formed at the ends of de
composing chains stops the development of further chain processes; it
cannot, however, prevent a decrease in molecular weight due to the ini
tial cleavage of the chain molecule as a result of either chemical action
or mechanical force. This undesirable effect may be reduced by using
nonvolatile monomers as inhibitors and plasticizers; terminating the
chain decomposition processes, these monomers simultaneously in
crease the length of the parts of the chain molecules cleaved. Probably
the use of polymer inhibitors, in which the inhibiting groups are con
tained in the molecules of such polymers themselves, would be still
better. In this case the event of inhibition would represent chemical
combination of the decomposing molecule with the polymer inhibitor
molecule. By regulating the molecular weight and number of active
groups in the polymer inhibitor molecule, we can gain the possibility
of not only maintaining the molecular weight, but of increasing it as
well as the degree of branching of the polymer to be stabilized.
In addition, the stabilization of polymers by solid particles of col
loidal dimensions is also possible. It would seem that the use of truly
soluble inhibitors should give a far greater probability that the inhibitor
molecules will encounter the torn-off ends of the chains. However, we
now know that practically all polymers exhibit well-defined structures
and that extraneous substances, including soluble ones, are arranged
among the elements of these structures. It is thus possible that the ad
vantages of inhibitors soluble in the polymer are not as great as it would
seem at first glance. At the same time, inhibition by reaction with solid
surfaces possesses a number of advantages, both in the selection of sub
stances and in improving the bond between the polymer and the pigment
or filler particles. The appearance of structuring in this case com
pensates for the drop in molecular weight. Dispersed inhibitors may
give satisfactory stabilization results, as well as the application of in
hibitors deposited on filler particles and pigments.
We should note one further category of phenomena that occur in
polymers - especially in crystalline polymers - during their use and
storage. Investigations of the structure of polymers in recent years
have shown an unexpected richness of structural forms and a close con
nection between these forms and the mechanical properties of the poly
mers. It is also known that under mechanical action or during storage
change occur in the structure of the polymers that are analogous to the
phenomena of aging of metals. The problem arises then of not only creat-