Intrinsic Fluorescence Spectroscopy Study Of The Vulcanization Process Of Rubber Materials

In this paper,the intrinsic fluorescence spectroscopy method was used to track the vulcanization process of different rubber materials with different vulcanization systems.The evolution of microstructure during the vulcanization process was systematically studied.According to the influences of curing time,temperature and compounding system on fluorescence spectra during,the vulcanization mechanism was proposed.On this basis,the kinetic parameters such as activation energy were calculated.Besides,microscopic activation energy was estimated by means of Han equation.In the peroxide vulcanization system of SBR,the intrinsic fluorescence spectrum reflects the true evolution of molecular chain and network structure when AD is used as a vulcanizing agent.With increasing curing time,the degree of cross-linking gradually increases,and larger conjugate degree leads to the decrease of fluorescence intensity.When the vulcanization process ends,the fluorescence intensity tends to be constant and the network becomes stable.When the curing temperature increases,the change rate of the fluorescence intensity increases and curing rate is accelerated.With the increase of the amount of AD,the changing amplitude of fluorescence intensity increases and cross-linking density increases.In addition,we use Han model to fit the kinetics process and obtain microscopic activation energy(76.91 kJ/mol).On this basis,DCP was used as a vulcanizing agent in this paper.Due to the presence of the benzene ring in DCP,the intrinsic fluorescence peak gradually shifts to longer wavelength with curing time increasing,and the amplitude of the peak intensity increases.This is mainly because the DCP participates in the formation of the conjugate network structure,which increases the conjugate degree of the cross-linked network.On this basis,the vulcanization process of sulfur vulcanization system,which is the more widely used in industry,was also studied by intrinsic fluorescence spectroscopy.The fluorescence peaks corresponding to accelerators,activators and vulcanizing agents in the sulfur vulcanization system are assigned respectively.The fluorescence intensity also decreases first and then tend to be constant.With curing temperature increasing,the fluorescence intensity changing rate is accelerated,and cross-linking speed increases.When the content of ZnO is more than 1 phr,the formation of conjugated network can be effectively activated.But when it is more than 3 phr,the characteristic peak of ZnO appears again in the late stage.Sulfur content has no effect on the changing rate of fluorescence intensity which means that it can not affect the curing rate.But,the increasing of sulfur content bring about the redshift of characteristic peak of the conjugate structure.The addition of accelerator accelerates the changing rate of fluorescence intensity and increases the curing rate.In addition,the intrinsic fluorescence spectrum was also used to study curing process of NBR.With the increase of curing temperature,fluorescence intensity changing rate increases,and cross-linking rate increases.The effect of ZnO in NBR is similar to that in SBR,but the difference is that the characteristic peak of ZnO becomes more obvious even when content is 1 phr.