Methyltrimethoxysilane(MTMS) was used to modify novolac resin (Novolac) to improve the thermal stability of Novolac. Siloxane-modified novolac resin (SN) was prepared by ester exchange reaction at the molecular level. The influence of catalysts

reaction time and reaction temperature on the molecular weight of SN was investigated

the results showed that

the best catalyst was acetic acid

the most appropriate reaction time was 4 to 6 hours

and the optimum vacuum distillation temperature was 110℃. The results of structural characterization of SN showed that the reaction of one methoxy group of MTMS and phenolic hydroxyl groups of Novolac occupied the dominant position. The results of thermal stability of cured SN showed that

compared to cured Novolac

under nitrogen atmosphere

the maximum decomposition rate temperature of cured SN100 increased by 80℃

the maximum decomposition rate decreased by 42. 94 %

and the char yield at 1000℃ increased by 8. 97%

meaning that the introduction of siloxane could greatly enhance the thermal stability of Novolac.