Preparation of dual-functionalized graphene oxide for the improvement of the thermal stability and flame-retardant properties of polysiloxane foam

Abstract

Polysiloxane foam (PSF) is a foam material with outstanding performance. However, the limiting oxygen index (LOI) of pure PSF is only 22.0 vol%, which can be attributed to combustible materials. In this work, graphene oxide (GO) was functionalized with hexachlorocyclotriphosphazene (HCCP) and 3-aminopropyltriethoxy-silane (APTS). The introduction of the functionalized GO into the PSF matrix has significantly improved the dispersion and flame-retardant properties of the final PSF composite. The char residue of PSF with 1.0 wt% functionalized GO content is 43.04%, which is considerably higher than that of the pure PSF (23.18%). Furthermore, the T_max of PSF with 5.0 wt% functionalized GO content has increased from 585.9 °C to 668.8 °C. The results of the cone calorimetry test indicate that modification with functionalized GO prolongs the combustion of PSF composites. The LOI value of PSF with 5.0 wt% functionalized GO content has increased from 22.0% to 27.6%. In addition, the peak heat release rate, total heat release, and total smoke production of PSF with 5.0 wt% functionalized GO content were decreased by 49.2%, 14.5%, and 62.2% relative to those of pure PSF. These results can be ascribed to the barrier effect of GO, the condensed-phase and gas-phase mechanisms of HCCP, and the bonding effect of APTS.