POLYMER OXIDATION AND ANTIOXIDANTSThe performance of polymer artifacts is adversely affected if degradation occurs during the various stages of polymer manufacture, fabrication, and subsequent exposure to the environment. Molecular oxygen is the major cause of polymer degradation and is responsible for the ultimate mechanical failure of polymer artifacts. The deleterious effect of molecular oxygen is accelerated by many other factors: sunlight; heat; ozone; atmospheric pollutants; water; mechanical stress; adventitious metal and metal ion contaminants.Polymer degradation during both thermal processing and weathering proceeds essentially through an autoxidative free radical chain reaction process, Scheme 1. This process involves (a) the generation of free radicals (Scheme la), (b) propagation reactions, which lead to the formation of hydroperoxides (Scheme lb and lc), and (c) termination reactions in which free radicals are eliminated from the autoxidizing system (Scheme 19, h, and i). Hydroperoxides are inherently unstable to heat, light and metal ions and readily decompose to yield further radicals (Scheme ld) which would continue to initiate the chain reaction. The role of hydroperoxides in the autoxidation process is to maintain the kinetic chain reaction, which would otherwise rapidly self terminate through radical coupling reactions of the main propagating species (Scheme 19, lh, Ii). This autoxidation process normally starts slowly but autoaccelerates leading, in most cases, to catastrophic failure of the polymer artifact.G. Pritchard (ed.), Plastics Additives