Synthesis And Properties Of Solvent-free Silicone Impregnating Resin

With the development of the high-speed locomotive, aerospace, etc, the demands for solvent-free silicone are increasing in our country. However, there is no suitable organic silicone impregnating varnish for the process of VPI (Vacuum pressure impregnation), the demand for these products basically rely on imports at the present stage.In this paper, the silicone prepolymer with vinyl and hydrogen groups respectively were prepared by hydrolysis and co-condensation of chlorosilanes respectively. Then the silicone impregnating resin was synthesized by the addition reaction polymerization of Si-CH=CH2 and Si-H groups. The recipe for synthesizing silicone resin was determined by adjusting the value of R/Si and the content of methyl and phenyl groups. The structure of silicone resin was characterized by FT-IR, GC-MS, Si-NMR, H-NMR analysis and Gel chromatogram. Results showed that the impregnated resin with vinyl and hydrogen structure were synthesized successfully and the ratio of methyl and phenyl from the obtained silicone resin satisfied the demand of pre-designed data. The viscosity of silicone varnish was in a suitable range and the polydispersity of its molecular weight was reduced by adjusting the synthesis process.Silicone impregnated resin has been studied, including the preparation by polysiloxane of different vinyl group and hydrogen group ratio, the heat resistance property. The curing process, the basic performance and electrical performance (including the volume electric resistivity, dielectric strength, dielectric constant) of silicone impregnating resin after curing were also researched. Results show that when the R / Si value and phenyl content of 1.50 and 44% respectively, the matrix containing vinyl resin and the crosslinking agent containing Si-H were prepared to mass ratio of 2.2:1, the impregnated resin has high heat resistance, low volatility, optimal moisture-proof performance, high mechanical strength, low dielectric loss, and good performance in application, which has been of excellent insulating structure.