Silicone rubber foam is increasingly used in applications, because it has the excellent properties of silicone rubber and foam materials. It has the high resilience of rubber, anti-aging, and the performance of foams such as sound absorption and shock absorption. Shock absorbers, gaskets (sealing grade IP68), sound insulation, insulation, aviation insulation and other performance requirements are relatively high. According to the cell structure, the silicone rubber foam is classified into a closed cell type, an open cell type, and a mixed type.
Closed-cell foamed silicone foam material has good shock-proof cushioning, sound insulation, heat insulation and flame-retardant and explosion-proof characteristics. It is mainly used in automotive fields for thermal insulation foam pipes for automotive air-conditioning, automotive shock absorption, and new energy. Foamed silicone gaskets for automotive batteries, etc.

At present, most automotive interior materials, such as floor, ceiling, steering wheel, and car seat, are polyurethane foams. This is because polyurethane foam technology is relatively mature and its performance meets the needs of use. On the other hand, polyurethane foam The price of the material is lower. However, polyurethane foams have poor weather resistance, are flammable, and release a large amount of toxic gases harmful to the human body during combustion. Therefore, with the promotion of foamed silica gel materials and the improvement of people's understanding, future foamed silica gel materials are expected to replace traditional polyurethane foam materials.

2.1 Density selection of foamed silica gel
The silicone rubber matrix has a density of 1.17 g/cm3. However, through the foaming treatment, the silicone rubber foam prepared in the current mature process can have a density of at least 0.16-0.20 g/cm3, which can be used for parts such as automobile seats and headrests; and conventional silicone rubber. The foam material (having a density of 0.45 g/cm3) is widely used for gap filling in parts such as sealing and shock absorption.

2.2 Flame retardant properties of foamed silica gel
One of the test methods commonly used to characterize the flame retardant properties of polymers is the vertical combustion method. The combustion mode is very close to the actual situation of object burning, so it can reflect the actual flame retardant effect of silicone rubber. The effect of the amount of flame retardant on the vertical burning performance of silicone rubber is shown in Table 2. It can be seen from Table 2 that the silicone rubber without flame retardant is completely burned; the silicone rubber with 40 parts of flame retardant has a vertical burning grade of FV-1, which has a certain self-extinguishing ability; 80 parts of flame retardant is added. The vertical burning grade of silicone rubber has reached FV-0 level and shows good self-extinguishing performance

2.3 Electrical insulation properties of foamed silica gel
With the increase of the amount of physical filler, the volume resistivity and surface resistivity of silicone rubber decrease, and the dielectric constant and dielectric loss factor generally increase. It can be seen that the addition of physical fillers impairs the electrical insulation properties of silicone rubber to some extent.