The choice of flame retardant depends on which flame retardant mechanism is suitable for the properties of the flame retardant.

1. Endothermic mechanism

Some flame retardants will decompose to form water when heated, and the water will evaporate and take away a lot of heat, so as to achieve the effect of flame retardant, which is the same as the principle of extinguishing fire with water. Such common flame retardants include borax, hydrated alumina, etc.;

2. Covering effect

When some flame retardants are heated, they will decompose to form a stable covering layer, which isolates the material from oxygen, so as to achieve the effect of flame retardant. Commonly used flame retardants include phosphate ester compounds and fireproof foam coatings;

3. Dilution effect

When some flame retardants are heated, they will decompose into a large amount of non-flammable gases (carbon dioxide, ammonia, chlorine chloride, etc.), which will dilute the air around the material and greatly reduce the concentration of oxygen, so as to achieve the flame retardant effect. The principle of dry powder fire extinguisher is the same, such common flame retardants include amine phosphate, amine chloride, amine carbonate, etc.;

4. Inhibitory effect

The combustion of some polymer materials is mainly a free radical chain reaction, and some substances can capture the active intermediates of the combustion reaction, inhibit the free radical chain reaction, and reduce the combustion speed until the flame is extinguished. Commonly used flame retardants are bromine, chlorine and other organic halogen compounds.