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Abstract

Bis(diisopropyl)thiophosphoryl disulfide (DIPDIS) is used as a sulfur donor vulcanizing system for cis-1,4-polyisoprene. It is shown that the network structure consists of poly- and disulfidic crosslinks at early stages of cure, simplifying at optimum cure to monosulfidic crosslinks. It is thought that pendent accelerator groups are bound to the rubber molecule at early stages of cure, but are subsequently replaced by cyclic sulfidic groups. The good thermal and thermal oxidative aging behaviour of the vulcanizate is due to the formation of zinc diisopropyldithiophosphate (ZDP) in situ.