A novel application of sulphur-containing antioxidants for the stablisation of polyolefins

Abstract

The in-service performance of polymers is greatly affected by processing. Mechanooxidation reactions are responsible for the early failure of processed polymers. During processing, the initial formation of macroalkyl and peroxyl radicals is followed by the formation of hydroperoxides which are chiefly responsible for further radical-generating and polymer degradative reactions. Therefore adequate stabilisation is essential for plastics products. Under normal processing conditions, most sulphur-containing antioxidants are partially converted to oxidation products at elevated temperatures. In most cases these reaction products are more effective antioxidants than the compound added initially. It is shown here that controlled oxidation processing of polymers in the presence of sulphur-containing compounds can provide a highly effective antioxidant system. This approach to processing can be used further to promote desirable polymer-antioxidant reactions.