Design and Synthesis of a Novel Block-Phenyl Silicone Resin

Abstract: Polysiloxanes are organic-inorganic hybrid polymers with good high-low-temperature resistance, radiation resistance and oxidation resistance, which make them widely applicated in aerospace, automotive, electronics, chemical industry and many other fields. Currently, the commercial liquid silicon resin is mainly solvent-based, which can be highly cross-linked by condensation of silanol groups with water released or by hydrolytic condensation of alkoxy groups at higher pressure and high temperature. Many limits exist while they are applicated as adhesives or as matrix resin in composites in both techniques and performance. On the basis of the POSS liquid silicon resin invented by our laboratory, a novel solvent-free liquid silicone resin with flexible segments in the backbone, was developed by hydrolytic copolycondensation of hydroxy-terminated polydimethylsiloxane and phenyl-trimethoxysilane in order to toughen POSS silicone resin, which are both innovatively and practically.The synthetic process parameter, such as catalyst, solvent, reaction temperature and time was studied and the properties of the cured redin were evaluated.1. The block-phenyl silicone resin was synthesized by controllable hydrolytic condensation reaction of Hydroxy-terminated polydimethylsiloxane and phenyltrimethoxysilane under certain conditions. And influences of raw materials, catalysts, reaction temperature, reaction time and degree of hydrolysis on synthetic block-phenyl silicone resin were investigated.2. The optimum synthetic process were found out:First, the hydrolytic condensation reaction were carried out at 80℃for 9h at the mole ratio of 1:2.5 of phenyltrimethoxysilane to water catalysed by hydrochloric acid, Then raised temperature and separate water. Finally, the product was obtained by distillation at reduced pressure rotacooling.3. The available structure of liquid silicone resin was proposed based on the characterized by the results of FTIR,1H-NMR,29Si-NMR, GPC and XRD.4. The curing behavior of the new type block-phenyl silicone resin and the relationship between the structure of curing agent and gel time was measured, and the relationship between the amount of curing agent and gel time was studied.5. By using DSC, the activation energy E of the thermal degradation of the curred resin was 43.0KJ/mol, and order of reaction and the dynamic equation of the thermal degradation reaction was dβ/dt=A0·exp(-△E/RT)·(1-β)=4.0·exp(-5181.6/T)·(1-β).6. The relation of tensile strength and the amount of the phenyl silicone resin was revealed out that the tensile strength increases first and then decreased with the increasing of the amount of phenyl silicone resin.
Key words: Hydroxy-terminated polydimethylsiloxane; Silsesquioxane; Hydrolysis condensation; Temperature resistance; Thermal degradation;

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