Mechanisms contributing to the autoxidation of hydrocarbon polymers

Hydrocarbon polymers and many polymers which contain hydrocarbon segments are oxidized by a free‐radical, chain mechanism. In most commercial polymers, radicals which initiate this chain reaction originate from such reactive products as hydroperoxides rather than from cleavage of CH or CC bonds. These intermediates are formed in many polymers by preoxidation reactions occurring during synthesis and formulation. The dependence of autocatalysis on the homolytic decomposition of hydroperoxides is evidenced by inhibition reactions in which peroxide deactivators are used rather than chain terminating stabilizers. Hydroperoxides are decomposed by certain types of stabilizers into nonradical products, and the oxidation of polymers which oxidize through these intermediates does not become autocatalytic. Sulfur compounds and high concentrations of carbon black inhibit oxidation of hydrocarbon polymers primarily by this mechanism. Other types of peroxides, e.g., diperoxides and cyclic peroxides, which may be formed during autoxidation of certain hydrocarbon polymers, are much more stable to decomposition by sulfur compounds.