Nitrosamine-safe thiuram disulfide and benzothiazole sulfenamide as a synergistic pair of accelerators for the vulcanization of rubber

In this study, the synergistic activities of the novel bis -(N-phenyl piperazino) thiuram disulfide (PPTD) and bis -(N-ethyl piperazino) thiuram disulfide (EPTD) with N-Cyclohexyl-2-benzothiazole sulfenamide (CBS) in the vulcanization of natural rubber was investigated. A comparison was made between the safe TDs/CBS systems and unsafe TMTD/CBS combinations in terms of their synergisms on curing and tensile mechanical properties. It was found that novel TDs have synergistic activity very effectively with CBS. The results indicated that EPTD/CBS has better scorch safety, cure rate index and mechanical properties compared to that of the unsafe TMTD during the vulcanization of rubber. Moreover, alkyl, instead of aryl substitution, on piperazine can enhance the reactivity of the synthesized thiuram disulfide. At 6:3 mM ratio of EPTD to CBS could be an effective accelerators system to replace the unsafe TMTD from the vulcanization of rubber with similar curing time, improved scorch safety, and better mechanical properties.