Except for a few synthetic rubber products, most synthetic rubber products, like natural rubber, are flammable or combustible materials. At present, the main methods used to improve flame retardancy are to add flame retardants or flame retardant fillers, and to blend and modify with flame retardant materials.
Hydrocarbon rubber includes NR, SBR, BR, IIR, EPR, EPDM, etc. Although NBR does not belong to hydrocarbon rubber, its flame retardant technology is very similar to hydrocarbon rubber, so it is classified as hydrocarbon rubber treatment. Blending with flame retardant polymers, such as PVC, gasified polyethylene, chlorosulfonated polyethylene, ethylene Vinyl acetate and other polymers, can properly improve the flame retardancy of hydrocarbon rubber. Adding flame retardants is an important way to enhance the flame retardancy of hydrocarbon rubber, and the synergistic effect of flame retardants is utilized to further improve the flame retardancy effect. The commonly used flame retardants are mostly organic halogenated flame retardants, among which perchlorocyclopentadecane, decabromodiphenyl ether, Chlorinated paraffins, etc. are more commonly used.
Halogenated rubber contains halogen elements, with an oxygen index generally between 28 and 45, and the oxygen index of FPM even exceeds 65. This type of rubber itself has high flame retardancy and self extinguishing upon ignition. Therefore, its flame retardant treatment is easier than hydrocarbon rubber.
The most representative type of rubber in this category is dimethyl silicone rubber, with an oxygen index of around 25. The actual flame retardant methods used are to increase its thermal decomposition temperature, increase the residue during thermal decomposition, and slow down the production rate of combustible gases.
The main way of flame retardancy is to slow down thermal decomposition and block the combustion process. The specific flame retardancy pathways are as follows:
1. Add one or more substances to change the thermal decomposition behavior of rubber, increase the thermal decomposition temperature of the prepared rubber, and reduce the combustible gas generated during decomposition.
2. The added substances can generate non combustible gases or viscous substances that isolate O2 when heated, or can absorb heat when heated, making it impossible to meet the three combustion factors (combustible, oxygen, and reaching the ignition point).
3. Add substances that can capture HO ·, interrupt the chain reaction, and terminate the flame propagation.
4. Change the structure or properties of rubber molecular chains, improve their thermal decomposition ability, or make them flame retardant.
Due to the good compatibility between rubber and various additives, the addition of various flame retardants is still an important means of flame retardant modification of rubber at present.