Cure modification of natural rubber containing benzothiazole accelerators by some modified thiocarbamyl sulfenamides

Abstract

The effects of N-cyclopentamethylene thiocarbamyl-N-(cyclohexyl,thiocyclohexyl)sulfenamide (CPCTS) and N-oxydiethylene thiocarbamyl-N-(cyclohexyl,thiocyclohexyl)sulfenamide (ODCTS) as cure modifiers on the vulcanization of natural rubber (NR) containing benzothiazole accelerators were studied. CPCTS and ODCTS were used separately with 2-mercaptobenzothiazole and N-oxydiethylene benzothiazole sulfenamide to determine their effects on these accelerators. CPCTS and ODCTS retarded the accelerators. Enhanced activity was found with respect to the torque, scorch, modulus, and tensile strength and was believed to be due to the formation of different intermediate components during the early stage of the vulcanization of NR. Reactions likely responsible for acceleration and retardation were explored. CPCTS and ODCTS provided better cure retardation than N-cyclohexyl thiophthalimide. The chemical characterization of the NR vulcanizates correlated with the physical properties obtained at 140°C. Stocks containing CPCTS or ODCTS produced mostly monosulfide linkages, which were affected when N-cyclohexyl thiophthalimide was used. This provided information concerning the heat-resistance properties of the vulcanizates.