Polymer Stabilization and Degradation

441 Pages·1985·6.74 MB·English

by  Peter P. Klemchuk (Eds.)

ACS S Y M P O S I U M SERIES 280
Polymer Stabilization
and Degradation
Peter P. Klemchuk, EDITOR
CIBA-GEIGY Corporation
Based on a symposium sponsored by
the Division of Polymer Chemistry
at the 187th Meeting
of the American Chemical Society,
St. Louis, Missouri,
April 9-12, 1984
American Chemical Society, Washington, D.C. 1985
In Polymer Stabilization and Degradation; Klemchuk, P.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
Library of Congress Cataloging in Publication Data
Polymer stabilization and degradation.
(ACS symposium series, ISSN 0097-6156; 280)
"Based on a symposium sponsored by the Division of
Polymer Chemistry at the 187th meeting of the
American Chemical Society, St. Louis, Missouri, April
9-12, 1984."
Bibliography: p.
Includes indexes.
1. Polymers and polymerization—Deterioration—
Congresses. 2. Stabilizing agents—Congresses.
I. Klemchuk, Peter P., 1928- II American
Chemical Society. Division of Polyme
III. American Chemical Society
St. Louis, Mo.) IV. Series.
QD380.P653 1985 547.7 85-9011
ISBN 0-8412-0916-2
Copyright © 1985
American Chemical Society
All Rights Reserved. The appearance of the code at the bottom of the first page of each
chapter in this volume indicates the copyright owner's consent that reprographic copies of the
chapter may be made for personal or internal use or for the personal or internal use of specific
clients. This consent is given on the condition, however, that the copier pay the stated per
copy fee through the Copyright Clearance Center, Inc., 27 Congress Street, Salem, MA 01970,
for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. This
consent does not extend to copying or transmission by any means—graphic or electronic—for
any other purpose, such as for general distribution, for advertising or promotional purposes,
for creating a new collective work, for resale, or for information storage and retrieval systems.
The copying fee for each chapter is indicated in the code at the bottom of the first page of the
chapter.
The citation of trade names and/or names of manufacturers in this publication is not to be
construed as an endorsement or as approval by ACS of the commercial products or services
referenced herein; nor should the mere reference herein to any drawing, specification, chemical
process, or other data be regarded as a license or as a conveyance of any right or permission,
to the holder, reader, or any other person or corporation, to manufacture, reproduce, use, or
sell any patented invention or copyrighted work that may in any way be related thereto.
Registered names, trademarks, etc., used in this publication, even without specific indication
thereof, are not to be considered unprotected by law.
PRINTED IN THE UNITED STATES OF AMERICA
In Polymer Stabilization and Degradation; Klemchuk, P.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
ACS Symposium Series
M. Joan Comstock, Series Editor
Advisory Board
Robert Baker Robert Ory
U.S. Geological Survey
Research Center
Martin L. Gorbaty
Geoffrey D. Parfitt
Exxon Research and Engineering Co.
Carnegie-Mellon University
Roland F. Hirsch
James C. Randall
U.S. Department of Energy
Phillips Petroleum Company
Herbert D. Kaesz Charles N. Satterfield
University of California—Los Angeles Massachusetts Institute of Technology
Rudolph J. Marcus W. D. Shults
Office of Naval Research Oak Ridge National Laboratory
Charles S. Tuesday
Vincent D. McGinniss
General Motors Research Laboratory
Battelle Columbus Laboratories
Douglas B. Walters
Donald E. Moreland
National Institute of
USDA, Agricultural Research Service Environmental Health
W. H. Norton C. Grant Willson
J. T. Baker Chemical Company IBM Research Department
In Polymer Stabilization and Degradation; Klemchuk, P.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
FOREWORD
The ACS SYMPOSIUM SERIES was founded in 1974 to provide a
medium for publishing symposia quickly in book form. The
format of the Series parallel
IN CHEMISTRY SERIES except that, in order to save time, the
papers are not typeset but are reproduced as they are submitted
by the authors in camera-ready form. Papers are reviewed under
the supervision of the Editors with the assistance of the Series
Advisory Board and are selected to maintain the integrity of the
symposia; however, verbatim reproductions of previously pub
lished papers are not accepted. Both reviews and reports of
research are acceptable, because symposia may embrace both
types of presentation.
In Polymer Stabilization and Degradation; Klemchuk, P.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
PREFACE
POLYMER DEGRADATION AND STABILIZATION have become increasingly of
interest to an international audience, and contributions to the body of
knowledge have come from scientists worldwide. The symposium upon
which this book is based was billed as international to encourage the
participation of scientists from many countries, especially because it was the
first Polymer Degradation and Stabilization Meeting of the Polymer
Division of the American Chemical Society since March 1977 in New
Orleans, and also because
stabilizers, had resulted fro
The initial call for papers for this symposium asked for reports in the
following areas, among others: new stabilizers, stabilizers of high perman
ence, new findings of degradation and stabilization mechanisms, stabilizing
polymers for severe environments, the impact of new polymerization
processes on polymer stability, the complexities contributed to stabilization
by the solid state, and polymer thermooxidation at ambient conditions. The
response was excellent. As a result, we were able to organize a comprehen
sive program for the symposium. We are grateful to the many contributors
of papers to the symposium and especially to those individuals who
submitted complete papers for inclusion in this volume.
A major objective of the symposium and of this symposium volume was
to attempt a review of the most important developments in polymer
stabilization of the last decade. The development of hindered amine
stabilizers was a major accomplishment in that decade and was truly an
international achievement. Early work on stable free radicals in the United
States, Germany, England, and the Soviet Union, among others, led in 1962
to the first synthesis of 2,2,6,6-tetramethyl-4-oxopiperidine-7V-oxyl, the N-
oxyl of triacetonamine. That first synthesis by Neiman, Rozantsev, and
Mamedova of the Soviet Union triggered interest and excitement among
scientists in many countries—Japan, France, England, the United States,
Switzerland, Italy, and Canada—and ultimately led to the development of
the hindered amine stabilizers. We had invited many of the scientists who
were involved in the early history of hindered amine stabilizers to come to
the symposium and to help us relive the hindered amine story. All could not
come, but many did participate and helped us to review the story of the
development of hindered amines and to gain an appreciation of that
development.
Three papers had been offered by scientists in the Soviet Union. There
were to have been papers on "The Discovery of Hindered Amine Stabilizers"
vii
In Polymer Stabilization and Degradation; Klemchuk, P.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
by Rozantsev, on "The Reactions of Aminyl Radicals and Mechanism of
Amine Regeneration as Inhibitors of Oxidation" by E. T Denisov, and on
"Nitroxyl Radicals and Polymer Stabilization" by A. L. Buchachenko. None
of the three authors was able to attend the symposium. However, Rozantsez
and Denisov have submitted their papers for this symposium volume.
This volume should serve as a good source for information on the status
of current developments on polymer degradation and stabilization. It
contains chapters on hindered amine light stabilizers from the major centers
that have contributed to the development of this important class of polymer
stabilizers. It contains contributions on stabilizers of increased permanence
from the two major centers engaged in studying polymer stabilizers of
reduced volatility and increased permanence—the laboratories of Scott at
the University of Aston in Birmingham, England, and the laboratories of
Vogl, formerly at the Universit
Polytechnic Institute of New York in Brooklyn. Chapters on phosphites by
Spivack and mechanisms of stabilization by aminic antioxidants by Pospisil
highlight those important stabilizer classes. Chapters on the photodegrada-
tion and stabilization of poly(phenylene oxide) and polycarbonate by Pickett
and Pryde, respectively, on the thermal degradation of polyvinyl chloride)
by Hjertberg and the late Danforth, on the thermal oxidation and
stabilization of polyethylene by Horng, on the thermal oxidation of UV-
cured coatings by Heyward, and on the photooxidation of polyester-styrene
graft polymers by Ranby all provide state-of-the-art information on these
important substrates. The chapter by Carlsson on y-irradiation of polyprop
ylene provides information on a subject that has gained importance due to
the advent of y-ray sterilization of plastic articles. Chapters on a computer
model to study the degradation and stabilization of polyethylene by Guillet,
on chemiluminescence in studying polymer degradation and stabilization by
Zlatkevich and Mendenhall, and on techniques for studying heterogeneous
degradation on polymers by Clough contribute significant information on
these important and timely subjects. The book closes with a paper on the
timely subject, biodegradable polyethylene, by Bailey.
Many people have contributed to the preparation and publication of
this volume. The efforts of the authors to prepare the manuscripts and share
the findings of their work are acknowledged with appreciation. The editorial
assistance of Bonnie B. Sandel of Olin Chemical Co., the typing and
proofreading assistance of Nancy Lovallo, Dianna DiPasquale, and Deny
Lounsbury, and the efforts of Suzanne Roethel and others at the American
Chemical Society Books Department are all acknowledged with apprecia
tion. The help of all these individuals and many others not named has been
crucial to the success of this project.
The ACS Petroleum Research Fund and the Polymer Division, Inc., of
the American Chemical Society provided financial assistance for the
symposium, which was used for the most part to help with the travel
viii
In Polymer Stabilization and Degradation; Klemchuk, P.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
expenses of symposium speakers from overseas. The Additives Department
of the CIBA-GEIGY Corp. also contributed to the success of the symposium
by providing secretarial, typing, mailing, and telephone support. The
contributions of all these sources are gratefully acknowledged.
PETER P. KLEMCHUK
Additives Department
CIBA-GEIGY Corporation
Ardsley, NY 10502
December 7, 1984
ix
In Polymer Stabilization and Degradation; Klemchuk, P.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
1
Introduction to Hindered Amine Stabilizers
PETER P. KLEMCHUK
CIBA-GEIGY Corporation, Ardsley, NY 10502
The hindered amine story is an interesting success story involving
participation by scientists throughout the world. The success of
hindered amines has partly been due to the free exchange of infor­
mation among scientists, so that the accomplishments of one group,
studying stable free radicals, could be picked up by those in other
groups, in other parts of the world, who were interested in stable
free radicals as polymer stabilizers. The mechanisms of stabiliza­
tion by hindered amines were somewhat mysterious in the beginning
since these compounds didn't fit any of the known stabilizer types
and known mechanisms. Since stable free radicals had been of inter­
est for their antioxidant activity as trappers of chain-propagating
peroxy radicals the triacetoneamine-N-oxyl and derivatives thus
were, at first, of interest as radical-trapping antioxidants. How­
ever, it wasn't long before the light stabilizing activity of that
class of materials was recognized and not much longer before practi­
cal versions of hindered amine light stabilizers were synthesized,
tested, and introduced for market development. Their high order of
effectiveness as light stabilizers encouraged many scientists to
investigate the mechanisms by which they functioned. We now know
much about those mechanisms and can marvel at the effectiveness of
hindered amines which apparently are dependent on what are very
small concentrations of N-oxyls for their activity.
There is much to learn and admire in the hindered amine story.
Chemists can take pride in how effectively they have worked together
across national boundaries to make hindered amine stabilizers an
important product group for the stabilization of polymers. This
introduction is a modest effort to review some of the early history
of stable-free radicals including triacetoneamine-N-oxyl. This
chapter was intended to serve primarily as an introduction to the
hindered amine review which took place at the symposium and inten­
tionally avoids covering material which other participants were
expected to present. It is a "light-touch" overview.
0097-6156/ 85/ 0280-0001 $06.00/ 0
© 1985 American Chemical Society
In Polymer Stabilization and Degradation; Klemchuk, P.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
2 POLYMER STABILIZATION AND DEGRADATION
Early Free Radical Research
Radical processes occur in many important chemical reactions
including:
polymerization electrical discharge reactions
halogenation photochemical reactions
combustion high energy-initiated reactions
autooxidation heterogeneous catalysis
enzyme processes
The radical nature of these reactions was identified through mechan
istic and kinetic analyses, but the lifetimes of the free radicals
involved are usually too brief to permit them to have been studied
directly. Thus, stable free radicals offer an opportunity to gain
basic information about free radicals and free radical reactions,
in particular:
1. elucidation of the natur
behavior; properties of its molecular orbitals; reasons for its
stabil ity;
2. elucidation of the kinetics and mechanisms of radical reactions
with stable radicals which can be observed and measured
directly;
3. elucidation of structures of liquids and solids containing
stable free radicals by the use of EPR and ESR techniques.
Stable free radicals are of particular importance to those who are
engaged in polymer stabilization because they play a key role in the
inhibition of autooxidation reactions.
The mechanisms of autooxidation reactions were elucidated
through the landmark research carried out at the British Rubber Pro
ducers' Research Association, where the kinetics of autooxidation of
olefins were studied in the 1940's and early 1950's. Some of the
key researchers engaged in that work were L. Bateman, J. L. Bolland,
G. Gee, A. L. Morris, P. Ten Have, among others. They contributed
enormously to our understanding of autooxidation reactions of
organic materials. Re-reading their papers produces appreciation of
their important work and emphasizes the debt we, in polymer stabil
ization work, owe them. That work established the following:
1. mechanisms and kinetics of autooxidation reactions of organic
materials;
2. free radical nature of autooxidation;
3. chain reaction nature of autooxidation;
4. hydroperoxides as the main oxidation products;
5. production of autooxidation initiation radicals from homolysis
of hydroperoxides;
6. inhibition of autooxidation by hydroquinone; the stability of
resultant semiquinone radicals terminated oxidation chains with
no chain transfer.
The work at the British Rubber Producers' Association and sub
sequent work by Bickel and Kooyman, Thomas and Tolman, among others,
led to the appreciation that a key requirement of oxidation inhibi-
In Polymer Stabilization and Degradation; Klemchuk, P.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
1. KLEMCHUK Introduction to Hindered Amine Stabilizers 3
tors was their ability to form stable radical intermediates. These
radical intermediates should be sufficiently stable so that they
don't participate in hydrogen abstraction from the substrate they
are stabilizing and therefore, not lead to chain transfer. In
Scheme I are shown the key steps in inhibition by the two main
classes of oxidation inhibitors, hindered phenols and secondary
aromatic amines.
Stable Free Radicals
The effectiveness of compounds yielding stable radical inter
mediates in the stabilization of organic materials led to interest
in stable free radicals in general. A review of the literature on
stable free radicals indicates that nitric oxide and nitrogen di
oxide have been known to be stable free radicals for a very long
time. In 1845, Fremy first described his salt which is an inorganic
N-oxyl derivative. The first report of an organic N-oxyl was by
Wieland and Offenbacher
and properties of diphenyl-N-oxyl. Diphenyl picrylhydrazyl was
recognized as a stable free radical in 1922 by Goldschmidt and Benn.
Structures of other early stable free radicals may be seen in
Figure 1. Those include several N-oxyl derivatives as well as gal-
vinoxyl, a stable-free radical derived from a hindered phenol.
These are only a few of the stable free radicals, especially N-oxyl
radicals, which have been discovered. Dr. Murayama of the Sanyko
Company included many such structures in a paper published in the
early 1970's (J.).
The first synthesis of 2,2,6,6-tetramethyl-4-oxypiperidine-N-
oxyl was described in a paper by M. B. Neiman, E. G. Rozantsev, and
Y. G. Mamedova 02). The synthesis was achieved by the oxidation of
triacetoneamine with hydrogen peroxide in the presence of sodium
tungstate. The key properties of the tetramethyloxypiperidine-N-
oxyl, which subsequently led to the whole family of hindered amine
stabilizers, were outstanding thermal and chemical stability.
Details of its properties are summarized in Figure 2. The compound
melted at 36°C It was stable to melting, recrystallization, and
distillation. IJ^underwent reactions of the carbonyl functionality
and had 6.1 x 10 spins/mole. The N-oxyl was reduced with hy
drogen on palladium catalyst to the corresponding hydroxylamine.
The N-oxyl remained intact after reactions with 1) hydroxylamine to
form the oxime, 2) semicarbazide to form the semicarbazone and 3)
2,4-dinitrophenylhydrazine to form the 2,4-dinitrophenylhydrazone.
The discovery of the 2,2,6,6-tetramethyl-4-oxylpiperidine-N-
oxyl was an important milestone in stabilization technology but the
triacetoneamine-N-oxyl was not useful by itself as a polymer stabil
izer because it is orange and would impart objectionable color to
polymers and because it has a relatively low molecular weight and
too high a vapor pressure for practical uses. In order to commer
cialize a practical stabilizer based on triacetoneamine-N-oxyl, the
following had to be achieved:
In Polymer Stabilization and Degradation; Klemchuk, P.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1985.