Compounding and testing of weather resistant rubber-I antioxidant effects on the accelerated light-ageing of rubbers of different network structures

Abstract

Three different systems were employed to vulcanize styrene-butadiene rubber SBR. They were: sulphur/mercaptobezothiazole disulphide, tetramethylthiuram disulphide, and a p-octylphenolformaldehyde resin/neoprene. The resulting vulcanizates had good physico-mechanical properties. Samples compounded with different antioxidants were aged by u.v. light and ozone at the critical deformation (30 per cent stretch). N-isopropyl-N'-phenyl p-phenylene diamine was found to be the most effective antioxidant; its efficiency was enhanced by using microcrystalline wax as a protective barrier. Combined antioxidants showed varying degrees of synergism and antagonism depending on the antioxidants and the vulcanizing system. The rubber ingredients and the products of their transformation during vulcanization have a great influence on the course of accelerated light-ageing. The sulphur vulcanization products have a stabilizing effect whereas the reverse is found for the phenolic resin vulcanizates. This discrepancy is discussed.