PREFACEFor centuries, the durability of products has been controlled by the properties of natu-rally occurring materials. The human skills to process them, experience gained overlong periods of observation, and local availability were the major factors in the selectionof a material. Rapid development of polymer synthesis in this century produced a greatvariety of new materials which were attractive for producers of finished goods. Thesematerials offered repeatable quality, ease of processing, and cost effectiveness. The firsttrials of these new materials did not include much durability testing because, even if thenatural products had not been very durable, there were many ways available to improveor protect them.

It was soon discovered that the new materials were substantially different and, al-though they had excellent initial properties, they usually suffered from limited durabil-ity. This has triggered an interest in the prediction of a material’s lifetime.

Each new branch of applied science suffers from the same problem of choice in itsinfancy stage. This choice is always between the art and the science. The “art” approachis always attractive because it makes room for immediate activity but seldom offers per-manent solutions. The"scientific" approach is slow but fundamental and only on such aproper foundation can a durable structure be built.

After several decades of fascination with new possibilities and randomly discoveredgood solutions, it becomes clear that the scientific approach is required. Materialsshould not only be durable but also recyclable and these, sometimes conflicting, require-ments produce an equation which cannot be solved by simple mathematics.

With this background, it appeared that this book could contribute only through ar-ranging the existing information in some orderly fashion. It is always easier to improvesomething if some milestones are properly selected and their position is known. On theother hand, it is equivalently important to indicate the essential skills required to solvethe problem and this must be done by dividing the multidisciplinary field to its compo-nent subjects. Finally, it seemed, at the time of writing, that a good inventory of knowl-edge and methods would also help in the iterative improvement of the currentinformation by those who are willing to read this book and develop the field further.

This has been the approach of the author. In addition, the precision of studies andtheir speed were also important considerations. Were the approaches correct? Was theirexecution successful? It will always be difficult to know the answer because many as-pects in science are a matter of opinion, and the unsurpassed advantage of science is thevariety of these opinions. Their challenge is what makes science prevail.

In selecting topics, every effort was made to emphasize the practical aspects of cur-rent efforts to produce materials according to agreed expectations. This is why there areseveral chapters designed to help the study of currently produced materials in a re-

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sult-oriented fashion. Where these two streams meet is the place in which this bookwants to be - to bring both sides (practice and theory) together.

The author of a book can only deliver information which is already available. There-fore, I would like to thank the authors of published information for their valuable inputbased on which this book was built. Most authors are cited in the book. Also, I would liketo thank many people in Atlas Electric Devices Company who gave me encouragement,data, and information used throughout the book. Some (but not all) are Randy Bohman,Margaret MacBeth, and Rudolph Leber who were kind enough to help me in finding re-quired information and who also offered their knowledge and assistance in developmentof some new methods of testing.

My two friends: Dr. Robert Fox and John Paterson devoted substantial amount oftime to read this book on various stages and offered invaluable suggestions which im-mensely improved the content.

George WypychTorontoSeptember, 1995

G. Wypychiv