PREFACE field is a remarkable one. Seventy years ago Baekeland made the first commercial synthetic polymer by combining small molecules. Since then these polymers have left little of our culture and technology untouched. The increase in output of the strongly innovative and pro ductive U.S. industry has been impressive, with a compound growth rate of approximately 11 percent between 1951 and 1977. In 1977 pro duction was more than 22 teragrams, corresponding to tens of billions of dollars worth of commerce, hundreds of thousands of jobs, and a favor able balance of trade of approximately two billion dollars. Synthetic polymers, which represent an outstanding intellectual achievement, serve an overwhelming number of man's needs. They com pete in increasingly sophisticated and demanding applications with metals, ceramics, and other materials. In many applications the lifetime under service conditions is critical for reasons of safety, health, security, and protection of capital investment. The list of such critical applications is very long and growing rapidly. High voltage underground power cables require a polyethylene dielectric which should not fail for many years. A most successful orthopaedic prosthesis, the artificial hip, uses polyethylene to replace the acetabular cup. Plastic shipping containers such as 55 gallon drums are used in interstate commerce for hazardous materials. Dentists regularly use composite restoratives with a polymeric matrix that is polymerized in the tooth. Plastic food packaging, which has had a profound role in lowering the rate of spoilage, requires careful control of additive migration during the use life. Structural components of some aircraft are composites with a plastic matrix. Synthetic polymers are used increasingly in automobiles.
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The need for fundamental and applied research on lifetime under service conditions is great. As a result, the subjects of dielectric break down, fatigue, wear, creep, fracture, oxidation, photodegradation, addi tive migration, etc., are increasingly important to the effective use of synthetic polymers. The development of a scientific basis for tests that predict accurately the useful service life is a primary need. In view of the above, it seemed appropriate to select Chemical and Physical Lifetime Limits of Macromolecular Materials as the topic of the Symposium. This provided an opportunity to focus on the lifetime aspect
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of the problem and to present the results of work in various chemical and physical disciplines in a more unified context. The results of this choice were gratifying. Four divisions of the Macromolecular Secretariat were joined by the Rubber Division of the American Chemical Society, the Division of High Polymer Physics of the American Physical Society, and the Engineering Properties and Structures Division of the Society of Plastics Engineers in arranging and presenting sessions at the Symposium. On behalf of the Macromolecular Secretariat' I thank W. J. MacKnight, S. L . Aggarwal, D. H . Reneker, S. S. Labana, J. M . Dealy, L . E . Smith, and V. T. Stannett who arranged the sessions of the Symposium. R. K.
National Bureau of Standards Washington, D.C. December 8, 1978
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