Studies on Cure Synergism—Part I: Effect of Bis(Diisopropyl) Thiophosphoryl Disulfide and Thiazole-Based Accelerators in the Vulcanization of NR

Abstract

Abstract The effect of the synergistic combinations containing diisopropyl thiophosphoryl disulfide (DIPDIS) and a thiazole type of accelerator on the vulcanization of NR has been investigated. MBT, N-oxydiethylene-2-benzothiazole sulfenamide (OBTS), and N-oxydiethylene-2-benzothiazole disulfide (OBDS) represent the thiazole-based accelerators. It has been established from the hplc study that diisopropylthiophosphoryl benzothiazole disulfide (DIBDS) is formed in the synergistic systems along with other rubber additives during the early part of cure. In this exploratory study, it has been observed that DIBDS enhances the torque, modulus, crosslink density, and the tensile strength of the vulcanizates. Chemical characterization of the fine network structure of the NR vulcanizates indicates that synergistic combinations produce about 80% of the monosulfidic linkages. The resultant vulcanizates thus become stable to oxidative aging at 100°C for a considerable length of time. The vulcanizates obtained with DIBDS also produce the same results.