Synergistic combination of 2-mercaptobenzothiazole (MBT) and nitrosoamine-safe thiuram disulfide as advanced rubber vulcanizing accelerators

In this study, we developed a combination accelerator system to synergistically improve the vulcanizing activity of 2-marcapto benzothiazole (MBT) with different nitrosamine-safe thiuram disulfides (TDs), namely, bis-(N-benzyl piperazino) thiuram disulfide (BPTD), bis-(N-phenyl piperazino) thiuram disulfide (PPTD), and bis-(N-ethyl piperazino) thiuram disulfide (EPTD), which can be used as nitrosamine-safe cross-linking accelerators for sulfur based rubber vulcanization. The results were compared with that of a conventionally unsafe TD, tetramethyl thiuram disulfide (TMTD) combined with MBT, to evaluate the efficiencies of these nitrosamine-safe TD accelerators for industrial applications. The curing and mechanical properties of rubber vulcanization were investigated to understand the synergism between MBT and nitrosoamine-safe TDs. The results indicate that novel TDs combined with MBT significantly improve the curing characteristics and mechanical properties following to the TDs with smaller molecular size and higher basicity. The MBT/BPTD system had higher modulus values because BPTD has a higher molar mass, which facilitates a better distribution of accelerators in the rubber matrix. Overall, the MBT/EPTD accelerator systems with equal molar ratios can compete with the curing rates, tensile strengths, and moduli of unsafe TMTD accelerator systems in the vulcanization of rubber.