Review of Basic Oxidation Processes in Elastomers

Abstract

Abstract The early studies of chain scission in the oxidation of rubber by Dr. E. M. Bevilacqua, and his subsequent work on the identification of the various acids, methyl ketones, and other volatile products of the oxidation reaction, have contributed much to our present knowledge of the nature of the processes involved in the oxidation of elastomers. His numerous research publications and review papers represent a significant segment of the world's literature on oxidation and aging of rubber. This introductory paper of the E. M. Bevilacqua Memorial Symposium is a brief review of our present understanding of some of the basic oxidation processes in elastomers. More extensive reviews of various aspects of the subject are available. This review is primarily concerned with the nature of the chemical reactions involved in the oxidation, degradation, and stabilization of elastomers. The mechanism of uninhibited autoxidation (based on model compound studies) will be compared with the more complicated sequence of reactions observed in the retarded autoxidation of elastomers which occurs in the presence of antioxidants. The oxidative degradation of physical properties will be considered in terms of the resultant effect of the two competing processes of chain scission and crosslinking. The role of antioxidants as stabilizers against oxidative degradation will be discussed from the standpoint of the mechanisms by which different types of stabilizers protect elastomers during aging and use.