Mechanism of the Zinc Dithiocarbamate-Activated Rubber Vulcanization Process: A Density Functional Theory Study

To elucidate the mechanism of sulfur vulcanization of butadiene-styrene rubber by zinc dithiocarbamate (ZDMC), the density functional theory method was used to investigate the nature of the vulcanization induction and vulcanization periods of the rubber vulcanization process mediated by ZDMC. A mechanism for the sulfur pyrolysis by bimolecular ZDMC during the vulcanization induction period is proposed in which sulfur is inserted to produce active sulfurating agents. The calculated results indicate that the cross-link precursors of perthiols are generated in the reaction of active vulcanizing agents and single chains of rubber molecules and that ZDMC could promote the cross-linking of cross-link precursors during vulcanization to form the vulcanizate. This work established the mechanism of Zn(II)-activated sulfur vulcanization, which provided theoretical insights into the development of the rubber vulcanization accelerators.