Flame retardancy, combustion, and ceramization behavior of ceramifiable flame-retardant room temperature vulcanized silicone rubber foam

Two types of ceramifiable flame-retardant room temperature vulcanized (RTV) silicone rubber foam containing mica power (MP) were prepared by using glass powder (GP) as fluxing agents and aluminum hydroxide (ATH) as flame-retardant agent, respectively. The flame retardant, combustion behavior, and thermal stability of ceramifiable flame-retardant RTV silicone rubber foams were investigated. The results show that GP is not conducive to the flame retardancy and thermal stability improvement of the foams. On the contrary, MP and ATH can significantly improve the flame retardancy and thermal stability at high temperatures of the foams. The foams with addition of MP and ATH can reach to a high limiting oxygen index value of 35.8 with V-0 rating in the vertical combustion test, and the total heat release and total smoke production of the foams are 21.0% and 61.7% lower than of the pure RTV silicone rubber foam, respectively. Furthermore, the structural and morphological changes of the foams under different pyrolysis conditions were studied, so as to reveal its ceramifiable mechanism under different fire scenarios. The results show that GP does not promote the formation of more char residue during pyrolysis, but it can greatly lower the ceramifiable temperature, resulting in a superior ceramic phase char residue. The foams including MP and ATH have a high char residue content; nevertheless, a comparatively higher temperature is necessary to create ceramic phase char residue.