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

Abstract

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.

Hydroboration of CO2 to Methyl Boronate Catalyzed by a Manganese Pincer Complex: Insights into the Reaction Mechanism and Ligand Effect

“…On the basis of our previous computational studies catalyzed by TM complexes, − all geometry optimizations in this paper were carried out at B3LYP-D3/BS-I level using Gaussian 09 program. , Other DFT functionals were tested, but no qualitatively different results were obtained (see Table S1 in the Supporting Information). BS-I denotes that the Mn center adopted the LANL2DZ basis set based on the effective nuclear potential energy approximation (ECP), and for other nonmetal atoms, we applied the Pople’s 2-zeta 6-31G­(d) all-electron basis sets .…”

Neutral Phosphine-Sulfonate Pd Complex-Catalyzed Copolymerization of 2-Methoxystyrene and Ethylene Polar Monomers: A DFT Mechanistic Study

“…Herein, the neutral phosphine-sulfonate Pd complex-catalyzed copolymerization reaction of 2-methoxystyrene with ethylene is studied. Following our previous research, − a DFT study using the Gaussian09 program at the ωB97XD/BSII//ωB97X-D/BSI level for all stationary points uses SMD for the toluene solvent (Solvation Model Based on Density) implicit solvation model for toluene, taking into account the influence of the solvent. − BSI denotes the 6-31G­(d) basis set for the main group atoms (C, H, O, P, S) in geometry optimization and the SDD basis set for Pd; BSII denotes def2-TZVP for the main group atoms and the SDD basis set for Pd in the single-point calculation . The Gibbs free energies obtained sum the electronic energy at ωB97X-D/BSII and free energy correction terms at ωB97XD/BSI.…”

Design of Vulcanization Intermediates with Low Steric Hindrance Contributing to Vulcanization Network Formation

“…Rubbers are widely used in everyday life, such as automobile tires, airplane tires, and seismic isolation materials. − Sulfur cross-linking, known as vulcanization, is an extraordinarily important process to endow rubbers with practical performances in the rubber industry. − For the vulcanization reaction, the widely agreed pathway is that stearic acid and zinc oxide (ZnO) produce vulcanization intermediates, further initiating the formation of vulcanization networks. , However, the steric hindrance of such vulcanization intermediates often hinders the formation of vulcanization networks, limiting the property enhancement of vulcanized rubbers. , How to further promote the formation of vulcanization network is still a challenge in the rubber industry.…”