2-t-BUTYLBENZOTHIAZOLE SULFENAMIDE ACCELERATED SULFUR VULCANIZATION OF POLYISOPRENE

The mechanism of 2-t-butylbenzothiazole sulfenamide (TBBS) accelerated sulfur vulcanization of poiyisoprene was investigated. Samples of compounded rubber were heated in a differential scanning calorimeter to preselected temperatures or degrees of vulcanization, the reaction stopped, and the products analyzed. TBBS polysulfides, formed from the reaction of TBBS with sulfur, react with the rubber chain to form benzothiazole pendent groups and free t-butylamine. The delayed action of TBBS accelerated sulfur vulcanization was shown to be due to an exchange reaction involving benzothiazole terminated pendent groups and TBBS. Crosslinking occurred very rapidly once the TBBS was depleted. Special reference was made to the role of the amine. Reaction mechanisms were proposed to account for the formation of products.