The Preparation And Performance Of Silicone Adhesion Promoters For Addition-cure Silicone Rubber

Addition-cure silicone rubber has been widely used in electronic and electrical equipment industry due to its excellent performance,such as resistance to high and low temperature,low surface energy,ozone-resistance,UV-resistance and electrical insulation.However,the molecular chains of polydimethylsiloxane are helical and crimped.The methyl groups around the spiral have a shielding effect on the polarity of Si-O-Si bonds,resulting in nonpolarity of polydimethylsiloxane.Furthermore,surrounding methyls are unreactive groups,which lead its poor adhesion to common substrates.Therefore,it is of great significance to enhance the adhesion of addition-cure silicone rubber.In this paper,two kinds of silicone adhesion promoters were synthesized,which was suitable for high-refractive index and low-refractive index addition-cure silicone rubber.Besides,the bonding mechanism was discussed.The main work as followed:Part one: Hydroxy dimethyl silicone oil(HMSO)was synthesized via the hydrolytic condensation reaction from dimethoxydimethylsilane with acidic cation resin as the catalyst.The synthesis process of HMSO was discussed and optimized.The optimal results were showed as follows: the molecular weight was 458,the molecular weight distribution index was 1.04 and the viscosity was 4.5mpa.s.Part two: Low-refractive index silicone adhesion promoter(GVHMS)was prepared through nonhydrolytic sol-gel reaction fromvinyltrimethoxysilane(VTMS),3-glycidoxypropyltrimethoxysilane(KH560)and HMSO.The synthesis process of GVHMS was discussed and optimized.The optimal results were showed as follows: the molecular weight was 1024,the molecular weight distribution index was 1.61,the viscosity was 7.0mpa.s and the refractive index was 1.4133.GVHMS had little iMpact on the light transmittance of silicone rubber indicatingit had good coMpatibility.The shear strength of silicone rubber and copper substrate reached 1.14 Mpa with addition of 2.0 phr GVHMS,which was183% higher than that of silicone rubber without the adhesion promoter.Part three: High-refractive index silicone adhesion promoter(GVPMS)was prepared fromVTMS,KH560 and diphenylsilandiol(DPSD).The synthesis process of GVPMS was discussed and optimized.The optimal results were showed as follows: the molecular weight was 498,the molecular weight distribution index was 1.95,the viscosity was 20.0mpa.s and the refractive index was 1.5185.GVPMS had little iMpact on the light transmittance of silicone rubber indicatingit had good coMpatibility.The shear strength of silicone rubber and copper substrate reached 1.70 Mpa with addition of 1.5 phr GVPMS,which was 295% higher than that of silicone rubber without the adhesion promoter.Part four: Adhesion performance of silicone rubber was studied by oxidation experiment,high temperature experiment and primer coating experiment,and the bonding mechanism models of primer coating and adhesion promoterwere established respectively.