Synthesis And Epoxidation Modification Of Phenylv Silicone Rubber

Silicone rubber has excellent temperature resistance,aging resistance,electrical insulation and chemical stability,widely used in medical,chemical,electronic and aerospace fields.Methyl vinyl silicone rubber has large molecular chain flexibility,side base resistance is small,low glass transition temperature and crystallization temperature,low loss factor from room temperature to high temperature,and poor damping performance,and can not meet the needs of damping applications in aerospace and other fields.In this paper,phenyl silicone rubber(MVPQ)with different phenyl content was prepared by anionic ring-opening polymerization.The SiO2 reinforced modification was studied,and MVPQ with different vinyl content was prepared.Epoxidized phenyl silicone rubber(EMVPQ)with different epoxy content was prepared to use direct epoxidation and the relationship between structure and properties was studied.The main results are as follows:(1)Synthesis of different phenyl content of MVPQ,phenyl content of 5%-25%,the yield of more than 90%;number average molecular weight(Mn)in 300,000 to 400,000,the molecular weight distribution index(PDI)is 2.1-2.4;As the phenyl content increases,the glass transition temperature of MVPQ increases from-117? to-74?.The MVPQ/silica composites were prepared with silica as a reinforcing agent.Studies have shown that as the phenyl content increases,the tan? peak value of the composite material shifts from-107? to-58?,the damping temperature range move to the high temperature zone;between-20??90?,the tan8 value of the composite material increases from 0.09 to 0.16,and the damping performance improves.(2)Different vinyl content of MVPQ was synthesized,the vinyl content was between 10%and 30%,and the yield was over 90%.The vinyl content was controlled by designing the ratio of monomers D4 and V4.EMVPQ with different epoxy content was prepared by direct epoxidation.The epoxy content was between 10%and 30%.The conversion of vinyl was more than 85%after 96 hours reaction.Before and after MVPQ Mn is similar,after the epoxy modification of MVPQ PDI slightly increased.The optimum reaction conditions for the epoxy modification of MVPQ were determined as follows:the reaction concentration was 3g/100 ml,and the reaction ratio of m-chloroperoxybenzoic acid and double bond was 1.3.The test results show that the Tg of MVPQ after epoxy modification is increased;the introduction of epoxy groups improves the rigidity of the main chain,making it difficult for the main chain to distort and degrade cyclically,so the thermal stability of epoxidized phenyl silicone rubber increases.(3)Synthesis of MVPQ with different phenyl content(vinyl content 10%),phenyl content between 5%and 25%,the yield of more than 90%,Mn between 200,000 and 350,000,but with phenyl content increases,Mn is greatly reduced,and the 25%phenyl content of MVPQ has Mn of 210,000,PDI of 2.2-2.8.There is no crystallization peak in MVPQ.With the increase of phenyl content,the Tg of MVPQ increases from-114? to-68?,and increases about 50 ?.With the increase of the phenyl content,the initial decomposition temperature of MVPQ in a nitrogen atmosphere was increased from 440? to 480?,which improved the high temperature resistance characteristics.