Reaction of Mercaptobenzothiazole with Rubber during Mastication

Abstract

Abstract Mercaptobenzothiazole (MBT), determined amperometrically in the acetone extract from an unvulcanized rubber-sulfur-MBT mix shows a loss of about 13 per cent of MBT. The results improve slightly when mixing is carried out at a low temperature (10° C) or in an inert atmosphere. After exploring the various possibilities, e.g., oxidation of MBT to MBTS or reaction with rubber it was concluded that main loss of MBT is due to a side reaction with nonrubber ingredients, extractable with acetone. Total MBT recovered when mixed with acetone extracted pale crepe or with synthetic cis-polyisoprene is about 98 per cent. In the absence of sulfur no appreciable reaction takes place even when MBT is heated with rubber at 145° C for 5 hours.