The effect of structure on thermal stability and anti-oxidation mechanism of silicone modified phenolic resin

In order to improve the thermal properties of the phenolic resin, silane with different degree of polymerization was introduced into phenolic resin by controllable reactions. Silicone phenolic resin was first synthesized via esterification reaction between methyltrimethoxysilane and novolac phenolic resin; then the degree of self-polymerization of silane was controlled by the hydrolyzation reaction. The designed structure of the hybrids was confirmed by Fourier Transform Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (1H-NMR and 29Si-NMR), and curing of the hybrids was performed to obtain samples for microstructure observation and anti-oxidation evaluation. In situ self-polymerization of the silane during both the hydrolyzation and the curing processes led to phase separation in the cured hybrids, and the size of the phase structure increased with the increase of self-polymerization degree of the silane. Thermogravimetric analysis and high-temperature oxidation test were performed, and silane introduction was found to be beneficial to the enhancement of both thermal stability and oxidation resistance. Anti-oxidation mechanisms for the phenolic resin modified with silanes at different polymerization degree were compared and discussed.