Study of Sulfur Vulcanization of Brominated Ethylene-Propylene Rubber

(1) It is shown that when BEPR is heated at 130–190 ° with various components of a sulfur vulcanizing system, the latter take part in nucleophilic substitution reactions with the combined bromine, and promote dehydrobromination of the polymer chains and crosslinking of the elastomer. (2) The effect of the components of the vulcanizing system on dehydrobromination is dependent on the acidity of the component, and their effect on vulcanization is dependent on the extent to which they activate the reaction of sulfur with the polymer. (3) Zinc oxide is itself a vulcanizing agent. In reacting with BEPR it forms ether crosslinks. (4) When BEPR is vulcanized by sulfur together with sulfur vulcanization accelerators and activators two types of crosslink are formed, namely strong C-C and C-O-C bonds and weaker sulfur bonds. This combination of bonds gives vulcanizates of increased strength.