Mixed type silicone rubber is made of linear high molecular weight polysiloxane (raw rubber) with molecular weight of 400,000 to 800,000, adding reinforcing fillers and various other fillers, and vulcanizing agent at high temperature vulcanization molding silicone rubber products. Because silicone rubber has the advantages of high and low temperature resistance, weather resistance, ozone resistance, electrical insulation, air permeability and physiological inertia, it has a wide range of applications in aerospace, electrical cables and medical treatment, especially in the field of high-tech plays an increasingly important role. However, the silicone rubber molecular chain contains a large number of C and H, so the silicone rubber itself is flammable, and it will continue to burn when it encounters an open flame, which greatly limits its scope of use. Increasing the flame retardant properties of silicone rubber products will greatly expand its scope of use, therefore, the development of flame retardant silicone rubber has very important theoretical value and application value. Although a lot of work has been done in the flame retardant technology of silicone rubber in China, there are still many problems in theory and application research, so the research of flame retardant silicone rubber is an enduring topic. With the deepening of research, the flame retardant system of a single flame retardant is increasingly unable to meet people's requirements for the performance of flame retardant silicone rubber, and the synergistic flame retardant system will be more and more favored, with the enhancement of environmental awareness, strengthening environmental protection has become a global human consensus. In the process of research on new flame retardants, we must adhere to the principle of reducing environmental pollution and maintaining fire safety, silicone rubber flame retardants are no exception, halogen-free, low smoke and low toxicity, high efficiency has become its main development trend, with the wide application of silicone rubber in various fields, silicone rubber flame retardant performance research is also a long way to go.
 The combustion of polymer is composed of four elements: heat source, oxygen, fuel and free radical reaction, all of which are indispensable. Therefore, improving the flame retardancy of the polymer is also achieved by inhibiting one or several of the elements. After a long period of research, it is found that silicone rubber can have the following different reactions during heating, ignition and combustion:
1. At high temperature rich in oxygen, side chain organic groups are oxidized and decomposed into small molecules, and at the same time, the cross-linking of silicon-oxygen bonds between molecules is caused to form cyclic oligomers;
2, the main chain unbuckle degradation, through high temperature hot air, silicone rubber molecular structure movement intensification, resulting in the main chain of silicon-oxygen bond and end hydroxyl condensation reaction, accelerate the degradation of silicone rubber;
3, random rearrangement reaction: in the non-active end group content of silicone rubber, if at a higher temperature, silicone rubber molecular structure to obtain enough energy, random rearrangement, rearrangement reaction once triggered, as the chain transfer process as the free radicals continue to cause silicone rubber molecules to react, and then combustion can develop and spread.
  Under the guidance of this theory, the relevant technical experts at home and abroad, after years of research and accumulation, summed up the following flame retardant mechanisms of silicone rubber, and are widely accepted by people, simple division can be divided into gas phase flame retardant mechanism, condensed phase flame retardant mechanism, free radical trapping mechanism and collaborative flame retardant mechanism. Therefore, to control the combustion of silicone rubber materials and enhance its flame retardant performance, it can be done in the following ways:
1, increase the thermal stability of the substrate;
2 Interfere with the path of generating free radicals, or capture free radicals;
3, the formation of non-combustible protective film;
4, the combustion system can absorb a lot of heat;
5, the formation of heavy mass gas to isolate fuel and oxygen;
6, reduce the concentration of oxygen and combustible gas.
  At present, the purpose of increasing the flame retardancy of silicone materials is mainly achieved by adding flame retardants. Flame retardants are additives that can improve the flame retardant resistance of materials, prevent the continuous burning of materials and inhibit the spread of flames. Flame retardants can be divided into halogenated flame retardants and halogen-free flame retardants, the flame retardant effect of halogenated flame retardants is ideal, once occupied most of the market of flame retardants for a period of time, and then people gradually found that halogenated flame retardants will produce a lot of smoke and toxic corrosive hydrogen halide gas when burned in heat, causing secondary damage, therefore, in February 2003, The European Union has issued a directive on the restriction and prohibition of the use of certain toxic and hazardous substances and elements in electrical and electronic equipment. Since 2004, relevant laws and decrees have been issued at home and abroad to prohibit the use of flame retardants containing harmful substances such as halogen in wire and cable, electrical equipment, building materials, coatings and other industries. In recent years, environmentally friendly high-grade flame retardants have received more and more attention, and with the strengthening of research on environmentally friendly flame retardants, environmentally friendly flame retardants are becoming more and more abundant, and it is easier to achieve industrialization, occupying an irreplaceable position in the flame retardant market.
  At present, environmentally friendly flame retardants mainly include: nitrogen flame retardants, phosphorus flame retardants, aluminum-magnesium flame retardants and silicone silicone flame retardants. Silicone flame retardant is a new type of halogen-free flame retardant with high efficiency, low toxicity, anti-melting drop and environmental friendly, and is also a carbon-based smoke suppressor. In addition to giving excellent flame retardant properties to the substrate, silicone flame retardants can also improve the processing performance and heat resistance of the material, which makes it a new direction for the development of flame retardants in the future.