The Preparation And Properties Of Silicone Resin Modified By Polyurethane

Silicone resin, which has the double property of inorganic and organiccompound and differs from other organic resin, is the extremely importantcategory of organic silicon material. Silicone resin performances goodhigh-low-temperature resistance, weather resistance, electricity insulation,aging resistance, which make them widely used in aerospace, chemicalindustry, electronics industry and many other fields. But Silicone resin haslow mechanical strength, poor adhesion and must be cured at high temperature,which limits its application in some fields. Polyurethane (PU) is an importantpolymer materials with excellent properties such as good mechanicalproperties, high abrasive resistance, chemical resistance,while it also exhibitspoor thermal stability, water resistance. The study of modified silicon by PU isexpected to improve mechanical properties, without substantially damagingthe thermal stability and weather resistance of silicon resin, might be used inmany fields such as coatings and adhesive.In this paper, MDI, polyester polyols, KH550, methyltriethoxylsilane,dimethyldiethoxylsilane, phenyltrimethoxysilane diphenyldimethoxysilane isused to synthesis a kind of modified silicon by PU. First, a polyurethane prepolymer is sunthesised by MDI and polyester polyols, then, KH550is usedto change the end groups from NCO-to Si-OR, and then the prepolymers withend groups Si-OR will mix with methyltriethoxylsilane,dimethyldiethoxylsilane, phenyltrimethoxysilane diphenyldimethoxysilane, bythe method hydrolysis-condensation, modified silicon by PU is prepared. Thefactors affect prepolymer reaction and hydrolysis reaction in the process werestudied, including reaction temperature, reaction time in the prepolymerreaction, and reaction temperature, reaction time, content of catalysts andwater, and the optimum reaction conditions is found out. Besides, Theinfluence of content of PU, value of R/Si ratio, Ph/R ratio,n(dimethyldiethoxylsilane)/n(diphenyldimethoxysilane) are also studied in thispaper. The result shows that with10%PU content, the optimum value of R/Siratio, Ph/R, n(dimethyldiethoxylsilane)/n(diphenyldimethoxysilane) is1.45,0.49,1.46.The structure of modified resin were characterized by FT-IR,29Si-NMR.The TG result shows that the initial decomposition temperature of modifiedresin with10%PU content is300℃in air, and final residual carbon content is65%, while the initial decomposition temperature of silicone resin is300℃and final residual carbon content is72%in air. Although the thermal residenceof modified resin is worse than that of silicone resin, it still performance goodproperties after heated in240℃for48h, and the film of modified resin with10%PU content has better chemical resistance and better mechanical properties.