The Influence of Vulcanization Agents on Vulcanization Kinetics of Chloride Butyl Rubber

BPR (brominated tert octyl phenolic resin) vulcanization system is one of the commonly used systems for CIIR (chloride butyl rubber). In the vulcanization process, there are two competitive reactions, the cross-linking reaction and the self-poly-condensation reaction of BPR. In this vulcanization system, the metal oxide, as vulcanization active agent, have a greater impact on the kinetics of these two competing reaction. The kinetics equation of overall reaction (including the two competitive reactions) and the BPR self-poly-condensation reaction with different amount of ZnO or MgO were obtained by non-isothermal DSC method. The results showed that ZnO would promote the overall reaction and the BPR self-poly-condensation reaction at lower dosage, the rate constant of overall reaction increased faster than BPR self-poly-condensation reaction rate constant with the increasing of the ZnO content, and when the ZnO content exceeded 7.5 phr, the rate constant of BPR self-poly-condensation reaction decreased; With the increasing of the MgO content, the rate constant of overall reaction and BPR self-poly-condensation reaction reduced, and the rate constant of self-poly-condensation reaction reduced much faster than the rate constant of the overall reaction when the content of MgO changed from 0.5 to 0.75. The cross-linking density was measured by the equilibrium swelling method. The results showed that with the increasing of ZnO content, the cross-linking density increased when it was less than 10 phr, and decreased when the ZnO content exceeded 10 phr. With the increasing of MgO content, the cross-linking density increased when it was less than 0.75 phr, and decreased when the MgO content exceeded 0.75 phr. The mechanical properties and the dynamic mechanical properties were investigated by the universal testing machine and the dynamic mechanical performance analysis (DMA), respectively. The results showed that the ZnO and MgO content had a great impact on the mechanical properties and the dynamic mechanical properties, and the variation trend of the cross-linking density was further confirmed by the corresponding variation of the properties.