| Vulcanization accelerator is one of the most important additives used in rubber processing.Currently,the widely employed vulcanization accelerators in rubber industry are mainly contained secondary amine such as sulfonamide and thiurams.However,these accelerators generate the nitrosamine compounds,which were deemed to be carcinogenic.Thus,it has become one of the major problems affecting on human health.Because of the absence of nitrogen atoms in the xanthate,nitrosamines would not be formed during the vulcanization.Thus,the xanthate is a class of non-toxic,rapid,as well as environmentally friendly vulcanization accelerators while it is seldom used in rubber industry for its poor thermal stability and easily decomposition.In this paper,silica is first activated by hydrochloric acid,and then the xanthate was grafted to the silica with chemical bonds,called silica-supported xanthate vulcanization accelerator,to enhance the dispersity and thermal stability of xanthate in natural rubber(NR).The effect from silica-supported xanthate accelerators on the vulcanization characteristics and related properties will be systematically exploration.So,pursuant the thorough work,the conclusion will be achieved and organized,which will provide theoretical basis and guidance for the application of xanthate vulcanization accelerator in rubber engineering.The specific research content and results are as follows:(1)The FTIR,XPS,SEM,and TGA were used to characterize the composition and structure of xanthate vulcanization accelerator and silica-supported xanthate vulcanization accelerator.The results showed that the xanthate was grafted on the silica by means of chemical bonds,the loading of xanthate on silica-suppolrted xanthate accelerators is 9.16wt%.The thermal stability of the xanthate vulcanization accelerator supported by silica was greatly increased.The initial degradation temperature(To)and the maximum degradation rate temperature(Tp)and the termination degradation temperature(Tr)were increased by 103.8?,130.8 ? and 202.1 ?,respectively,the thermal degradation activation energy increased by 70.04 kJ·mol-1.(2)Xanthate vulcanization accelerator can only be used for low-temperature vulcanization of rubber(<120?).After grafting xanthate on silica,the temperature at 145?can normally vulcanize NR,and the scorch time is prolonged,and the processing safety of the compounded rubber is obviously improved;the vulcanization flattening period is widened and it is not easy to return to the original.It is shown that the silica-supported xanthate vulcanization accelerator(accelerator SSX)prepared by the accelerant prepared in this paper has a good vulcanization-accelerating effect on natural rubber and can be cured by a conventional operation process.(3)The study of the vulcanization kinetics of the mixture of accelerator M and accelerator SSX with DSC showed that the activation energy of accelerator SSX system was higher than that of accelerator M system,and the curing rate was lower than that of accelerator M system.The degree of vulcanization and the vulcanization time of accelerator SSX and accelerator M systems all satisfy the power equation.RPA studies showed that the Payne effect of accelerator SSX compound was weaker than that of accelerator M compound,and the interaction between white carbon and natural rubber was enhanced.(4)The free sulfur content of the accelerator SSX system was more than that of accelerator M,and the cross-linking density was lower than that of accelerator M.The SEM analysis of the cross-section of the vulcanized rubber shows that compared with the vulcanizate of the accelerator M system,after the xanthate is loaded on the silica,the dispersion of the silica in the natural rubber matrix isimproved,and the interface binding is enhanced.The tensile strength and wet skid resistance of the accelerator SSX vulcanizates are higher than that of the accelerator M systems. |
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