酚醛/硅改性环氧共混物空气环境降解残留物结构及组分研究OA北大核心CSTPCD

The epoxy-polysiloxane copolymer(ES)was synthesized by condensation reaction of hydroxy-terminated polydimethylsiloxane(HTPDMS)and bisphenol A epoxy resin(CYD-128),and then blended with phenolic resin to modify and obtain polysiloxane modified epoxy/phenolic blend(ES/PF).Thermal properties of ES/PF blend and the chemical structure and composition of pyrolysis residues at different temperatures were investigated by thermogravimetry-differential scanning calorimetry(TGA-DSC),fourier transform infrared spectroscopy(FTIR),scanning electron microscopy with energy dispersive spectrometer(SEM-EDS),and X-ray photoelectron spectroscopy(XPS).The results show that,compared with pure phenolic resin,the residual yield of ES/PF blend increases by 438％at 800 ℃ in air atmosphere,and the maximum heat release rate decreases from 21.98 W/g to 14.93 W/g.However,under N2 atmosphere,the residual yield decreases slightly by 14.3％.In addition,the hybrid structure rich in Si-Ox in the pyrolysis condensed phase of ES/PF blend system within 430-600 ℃ plays a key role in the stable formation of carbon layer,effectively delaying and inhibiting the further degradation of resin,and thus improving the carbon residue rate.When the temperature exceeds 430 ℃,the existing form of silicon element in the residue changes significantly,from SiO2(accounting for more than 80％)at 430 ℃ to hydrated silica(SiO2·nH2O)at 600 ℃.These results fully indicate that the silicon element can significantly improve the carbon residue and thermal stability of phenolic resin under thermal oxygen condition,but its influence is suppressed to a certain extent under N2 conditions,which may be attributed to the oxygen absorption mechanism of siloxane groups during pyrolysis process.In addition,the structure and composition of pyrolysis residues of ES/PF blend system have a positive effect on improving the thermal residual strength and ablation resistance of the material.