Most silicone rubber products are inflammable. By adding flame retardant filler and flame retardant filler and blending with flame retardant material, the flame retardant property of synthetic silicone materials can be improved. In addition, the introduction of ignition monomer in polymerization reaction is also an effective method in flame retardant process, and improving the crosslinking density of silicone rubber products is also beneficial to flame retardant. Next, a brief introduction - the flame retardant technology.
1.hydrocarbon
Vertical rubber includes NR,SBR, BR,lIR, EPR, EPDM, etc. Although NBR does not belong to the vertical class, its flame retardant technology is very similar to that of the vertical class, so it is classified as synthetic silicone rubber treatment.
The oxygen index of C-silicone rubber is between 19 and 21, and the thermal decomposition temperature is between 200 and 500° C. The heat resistance and flame retardant properties of C-silicone rubber are generally poor, and the decomposition products of combustion are mostly flammable gases. The common methods of this silicone rubber fire prevention are as follows:
By blending with polyvinyl chloride, gasified polyethylene, chlorosulfonated polyethylene, vinyl acetate and other polymers, the flame retardant property of vertical silicone rubber can be improved appropriately, so as to improve the flame retardant property. Attention should be paid to the mixing ratio and co-crosslinking of blends.
Adding flame retardants to vertical silicone rubber is an important way to improve its flame retardancy, and the synergistic effect of flame retardants is further improved. The common flame retardants are mainly halogenated flame retardants, mainly perchlorocyclopentane, decabromodiphenyl ether and chlorinated paraffin. Among them, antimony is the main inorganic flame retardant, followed by zinc borate, alumina hydrate, ammonium gasification and so on. In use, it should be noted that free halide flame retardants cannot be contained, because in the process of processing, free halide will corrode equipment and molds, and have an adverse effect on the electrical and aging properties of silicone rubber. In addition, attention should be paid to the adverse effect of the amount of flame retardant on the mechanical properties of silicone rubber.
Add flame retardant inorganic filler, such as calcium carbonate, clay, talc, white carbon black, aluminum hydroxide, etc., to minimize the ratio of flammable organic matter. Calcium carbonate and alumina nitride have endothermic effects during decomposition. This will make some physical and mechanical properties of the rubber material decline, the filling amount can not be too large.
Through the experiment of increasing the crosslinking density of silicone rubber, it is proved that increasing the crosslinking density can increase the oxygen index. So as to improve the flame retardant property of silicone rubber. The reason lies in the increase of thermal decomposition temperature of rubber. This method has been used in the production of ethylene-propylene silicone rubber.
2.halogenated rubber
Halogenated gels contain halogen elements, and their oxygen index is generally between 28 and 45, and the -Fpm oxygen index even exceeds 65. The higher the halogen content of common halogenated silicone rubber, the higher the oxygen index; This silicone rubber itself has a high flame retardant, can be out of the fire. So its flame retardant treatment is simpler than light rubber. In order to improve the flame retardancy of halogenated silicone rubber, flame retardants are often added.
3.composite chain glue
The most representative silicone rubber is dimethyl silicone rubber, its oxygen index is about 25, the thermal decomposition temperature of 400~6001. The actual flame retardant way is to increase the thermal decomposition temperature, increase the residue in the process of thermal decomposition, and slow down the generation rate of combustible gas.