Situ preparation of SiO₂ on graphene-assisted anti-oxidation for resol phenolic resin

Easily oxidized group of traditional phenolic resin (PF) results in poor oxidation resistance at high temperature, which is unable to satisfy the requirements of advanced aerospace vehicles for high-performance application, especially ablation resistance. In order to improve the oxidation resistance of PF, a SiO₂/RGO binary hybrid nanomaterial assisted anti-oxidation for PF was designed. Here, we reported a simple sol-gel process and high temperature reduction for synthesis of dispersed SiO₂ nanoparticles on graphene (G-S). The designed structure of G-S was confirmed by FTIR, XRD, SEM and TEM. Introduction of G-S into PF (P-G-S) was beneficial to enhancement of oxidation resistance in whole temperature range (0–1000 °C). P-G-S-3 (3 wt.% of G-S) exhibits both lower thermal oxidative decomposition rate and higher termination temperature of thermal oxidative decomposition (increase from about 750 °C up to 900 °C) than those of neat PF in air. In addition, P-G-S-3 decomposed by thermal oxidation in air (at 557 °C, weight loss> 30 wt.%) later than neat PF (at 519 °C, weight loss> 20 wt.%). What's more, compared to the collapse of skeleton structure and few residual fragments of neat PF, P-G-S-3 showed greater oxidation resistance which resulted in the retention of a large number of aromatic C-C, methylene and different kinds of ether bond at temperature from 550 °C to 700 °C by FTIR and XPS. The section of P-G-S-3 expresses skin lamination that can act as a barrier to slow down the diffusion of oxygen into resin matrix. And SiO₂ on the surface protected the matrix continually as indicated from the SEM analysis.