Vulcanization Chemistry. Comparison of the New Accelerator N-t-Butyl-2-Benzothiazole Sulfenimide (TBSI) with N-t-Butyl-2-Benzothiazole Sulfenamide (TBBS)

Abstract

The sulfur vulcanization chemistry of cis-polyisoprene formulations accelerated with N-t-butyl-2-benzothiazole sulfenimide (TBSI) is compared to the chemistry of equivalent formulations accelerated with N-t-2-benzothiazole sulfenamide (TBBS). High performance liquid chromatographic analysis (HPLC) is utilized to examine the kinetics of accelerator-sulfur disappearance and the formation-appearance profiles of extra-network cure intermediates across the vulcanization process for stocks with a wide range of sulfur/accelerator ratios. Some unique features of TBSI vulcanization that distinguish it from TBBS are defined. A major distinction is the apparent consecutive step-wise kinetics of accelerator decay across the vulcanization process. A sequential reaction process may be indicated. Evidence is also offered that BtS_xBt(x=2→6) is the crosslink precursor in TBSI vulcanization just as with TBBS formulations.