The Formation of Crosslink Precursors in the Sulfur Vulcanization of Natural Rubber

Abstract

Abstract With the accelerator MDB and with MBTS-sulfur, the addition of a relatively small amount of the zinc-accelerator complex (1) caused rapid formation of model crosslinks in 2-methyl-2-pentene under conditions in which neither model crosslink precursors nor model crosslinks were formed appreciably in its absence. In the accelerated sulfur vulcanization of natural rubber, zinc complexes promote both the formation and subsequent reactions of crosslink precursors. At 140°C, the reaction of MBTS-sulfur with 2-methyl-2-pentene gives a disulfidic model crosslink precursor derived by substitution entirely at the methylene site. At 150°C, or in the presence of the zinc-accelerator complex (1) at 130–140°C, precursors are derived by substitution at methylene and methyl sites.