Silicones typically contain only four elements: carbon, hydrogen, oxygen and silicon, so they break down during combustion to produce water, carbon dioxide and silicon dioxide. Silica produced in the combustion process of silicone resin can be uniformly covered on the surface of the fuel to form a layer of hard shell layer, to prevent the fuel melting dripping effect; At the same time, the silica is also a diffusion shielding layer, which can prevent the diffusion of the vaporized organic matter generated by the thermal decomposition of the internal polymer material at high temperature to the combustion zone. Silica shell layer has low thermal conductivity, good heat insulation effect, can block the heat transfer during combustion. The flame-retardant effect of silica hard shell produced in the combustion process of silicone resin on polymer materials can be realized by the combined effect of various effects, and this flame retardant effect is realized according to the condensed-form flame retardant mechanism.