PREFACE
Downloaded by KAOHSIUNG MEDICAL UNIV on June 6, 2018 | https://pubs.acs.org Publication Date: May 5, 1996 | doi: 10.1021/ba-1996-0249.pr001
POLYMERS WERE ORIGINALLY N I TRODUCED into commercial use
as bulk structural materials primarily because they were inexpensive and easy to form compared with existing alternatives such as metal and wood. They were, how ever, subject to deterioration due to a variety of environmental factors, in cluding light, mechanical stress, temperature, pollutants, and others. In particular, because most common macromolecules consist primarily of carbon and hydrogen in a reduced state, and because oxygen is abundant in most terrestrial applications, polymers are highly susceptible to degrading oxidation reactions. Because of this susceptibility, polymers quickly gained a reputation for low reliability; indeed, during the 1950s and 1960s, the word plastic" became commonly associated with the concept of "cheap" or "poor quality". 4
Today, polymers are used in ever-widening applications, and there is a growing emphasis on their durability and reliability. This emphasis results partly from increased consumer demand for quality in products. In addition, the existing paradigm of easy disposal and replacement of polymeric products is becoming much less attractive because of emerging environmental concerns: there is a growing awareness that enhanced lifetimes of polymeric materials could reduce the energy consumption needed in the manufacturing of materials and could also help alleviate the burden of solid waste. Moreover, there are now many instances in which molecular engineering of polymer-based materials has provided properties uniquely suited to meet a wide range of "high-tech" applications, including structural, surface-protective, electronic, and optical uses. These applications frequently have very high performance demands and/or high cost, which makes material stability of paramount importance. Polymers have come into widespread use primarily during the latter half of this century. As a result, work on their long-term aging characteristics is still in the early stages compared with, for example, metals, for which stability optimization through compositional and processing changes has been under experimentation over several millennia. The stability of polymers is an ex ceedingly complex problem, and this complexity remains an impediment to scientific progress in this area. Controlling degradation requires understanding of many different phenomena, including the diverse chemical mechanisms underlying structural change in macromolecules, the influence of polymer morphology, the complexities of oxidation chemistry, the intricate reaction pathways of stabilizer additives, the interactions of fillers and other ingredi ents, as well as impurities, and the reactive-diffusion processes that often take place (oxygen or other reactants coming in, and additives going out). Finally comes the difficulty of understanding the relationship between the numerous xiii Clough et al.; Polymer Durability Advances in Chemistry; American Chemical Society: Washington, DC, 1996.
Downloaded by KAOHSIUNG MEDICAL UNIV on June 6, 2018 | https://pubs.acs.org Publication Date: May 5, 1996 | doi: 10.1021/ba-1996-0249.pr001
changes in material composition that occur upon aging (which may be inhomogeneous on both micro- and macroscopic scales), and the observed changes in the physical properties and/or failure mechanisms of interest for the ma terial (e.g., mechanical strength, cracking, color, or electrical properties). This book provides an overview of the state of the art i n the science of polymer durability. Its 39 chapters are written by internationally recognized experts in the major technology areas of the field. The book is organized into three main sections covering degradation, stabilization, and lifetime predic tion. The degradation section discusses fundamentals of the molecular mech anisms by which polymers undergo aging and deterioration, particularly under environments of U V fight (as in outdoor exposure), or of thermal exposure. This section also describes a variety of important analytical techniques used for studying degradation, with special emphasis on the very sensitive technique of chemiluminescence. The second section of the book covers major types of additives used for polymer stabilization during processing, long-term (elevated temperature or room temperature) applications, and U V exposure. Various chapters describe the action mechanisms of different stabilizer types, and the effects of these additives on physical property retention. Several chapters discuss the problem of migration and retention of stabilizer additives in materials. Other stabilization-related topics include the development of specialized protective coatings and the influence of blends, copolymers, and fillers on stability. The final part of the book discusses progress in developing methods for predicting the aging rate and lifetime of a material in a particular application. These meth ods can involve the design of effective accelerated aging tests combined with modeling of aging processes. Also included in this section is a chapter on mod eling of degradation during melt processing. ROGER L. CLOUGH
Sandia National Laboratories MS 1407, P . O . Box 5800
Albuquerque, NM 87185-1407 NORMAN C. BILLINGHAM
School of Chemistry and Molecular Sciences University of Sussex Falmer, Brighton BN19QJUnited Kingdom KENNETH T. GILLEN
Sandia National Laboratories MS 1407, P.O. Box 5800
Albuquerque, NM 87185-1407
February 14, 1995 xiv Clough et al.; Polymer Durability Advances in Chemistry; American Chemical Society: Washington, DC, 1996.
