Preparation And Properties Of Flame-Retardant Ceramizable Liquid Silicone Rubber Foam

Silicone rubber foam was a versatile material that combined the benefits of foams and rubbers,and found extensive application in various industries.Such as clean-energy vehicles,architecture and aerospace.Among different types of rubber foam,liquid silicone rubber foam（LSRF）has gained more attention due to its environmental friendliness.However,the porous structure of LSRF limited its application in fire protection,as it promoted rapid ignition and sustained combustion during exposure to open flames.Furthermore,when LSRF were ignited,it decomposed into loose silica without any mechanical strength,further limited its fire protection applications.（1）The effects of inorganic flame-retardant fillers on the rheological properties,mechanical characteristics,flame retardant properties,thermal stability and pore shape of the liquid silicone rubber foam were examined.The results indicated that the addition of inorganic fillers enhances the apparent viscosity of the based-rubber which helped form in more regular and smaller bubble pores in the formation.Added fillers could enhance the mechanical properties of LSRF,ATH would improve its flame-retardant properties significantly,but decreased its thermal stability.In this paper,when the content of aluminium hydroxide was 60 phr,the comprehensive mechanical properties of the flame-retardant liquid silicone rubber foam were the best.The compression set was only 2.1%,the density was0.38 g/cm³,the 25%compression stress reached 275.3 k Pa,the maximum tensile strength was 447 k Pa,the ultimate oxygen index was 33.1%,and the flame-retardant grade reached UL94-0.（2）The influence of ablation temperature on the surface morphology,pore skeleton morphology,mechanical characteristics,chemical composition and phase structure of the ceramic silicone rubber foam was investigated.The results showed that ATH and LSRF decomposed at 295°C and 472°C respectively,small-molecular gas were generated and escaped from the surface,which resulted in a pore-like structure in the vesicular skeleton.With the LSRF volume shrinks considerably,the morphology of the bubble skeleton changed from a cavity to a compact structure as the ablation temperature increased from 25°C to700°C,and the three-point bending strength increased from 0 MPa to 4.4 MPa.When the ablation temperature was increased from 700°C to 900°C,there was no change in the volume of the products.The high-strength eutectic structure Al₂Si₂O₅（OH）₄ at the pore skeleton,and the strength was enhanced from 4.4 MPa to 15.4 MPa.