Preparation And Properties Of Epoxidized Silicone Rubber Composite Reinforced By Fumed Silica

Epoxidized silicone rubber(ESR)is a novel kind of silicone rubber,which is synthesized by introducing epoxy group into molecular chain of silicone rubber through chemical modification.Compared to methyl vinyl silicone rubber(MVQ),the cold resistance of this new type of silicone rubber was improved.At the same time,the polarity of its molecular chain was increased,which also improved the adhesive property of silicone rubber and metal.In this paper,it was found that the molecular weight distribution of the obtained silicone rubber becomes smaller by prolonging the reaction time of the synthetic catalyst and using anionic ring-opening polymerization(AROP)method.As a result,the methyl vinyl silicone rubber with different vinyl content was synthesized by using these methods above.The molecular weight of silicon rubber is between 200,000-300,000,and the polydispersity is less than 2.In addition,by using 3-chloroperoxybenzoic acid(m-CPBA)as oxidant which could directly epoxidize methyl vinyl silicone rubber,the silicone rubber with epoxy degree from 5%to 30%was prepared.Furthermore,the epoxidized silicone rubber/fumed silica(100/40)composites were prepared by mechanical mixing and the structure and properties of these composites were studied.The results showed that the dispersibility of fumed silica in epoxidized silicone rubber matrix was improved and the Payne effect was weakened with the increase of epoxy degree.Meanwhile,the effect of the peroxide amount on the tensile strength of the composites was studied.It was found that in the case of adding 0.08 phr of a vulcanizing agent and a silicone rubber having an epoxy degree of 10%to 20%,the composite material can obtain a higher tensile strength.The DMTA test showed that both the peak value and peak width of the loss peaks increased with the increase of epoxy degree.The DSC test indicated that when the epoxy degree was in the range of 5%to 30%,the glass transition temperature(Tg)of the composites changed from-122.04? to-107.51?.The TGA test showed that the heat resistance of the composites improved slightly with the increase of epoxy degree when the epoxy degree was less than 10%.Moreover,the introduction of epoxy group facilitated the adhesion of silicone rubber and aluminum sheets.Silicone rubber with 20%epoxy degree has the highest shear strength,which reaches 35.2 N cm-2.Finally,we tried to carry out epoxidation of silicone rubber by peroxyformic acid in situ generated by formic acid and hydrogen peroxide.Different solvents(toluene,cyclohexane,n-heptane,cyclohexanone/dimethylbenzene,cyclohexane/n-heptane),different phase transfer agents(PEG,Tween-80,OP-10),different reaction temperature(30?,40?,50?)and reaction ratios were tried,but the epoxidation was not achieved.