The main reason why the flame retardant plays a flame retardant role is that it can prevent or inhibit its physical change or oxidation reaction during the combustion of the polymer. Compounds that can have one or more of the following flame retardant effects can be usedflame retardant.

1. The endothermic effect

The compound is decomposed by heat or releases crystal water or dehydration, and the temperature rise of the material is inhibited due to its heat absorption, thus producing a flame retardant effect, which is called an endothermic effect. Such as borax, aluminum hydroxide, calcium carbonate and so on and thus play a flame retardant effect.

2. Coverage effect (isolation effect)

Flame retardant at a higher temperature to generate a stable coating or decomposition to generate a foam-like substance, covering the surface of the polymer, so that the polymer material due to thermal decomposition of flammable gas is difficult to escape, and the material from the role of heat insulation and isolation of air, so as to achieve the effect of flame retardant. Such as phosphorus ester compounds and fire retardant foaming coatings.

3. Dilution effect

The mechanism of action is that a large amount of non-flammable gas can be generated during thermal decomposition, so that the flammable gas generated by the polymer material is diluted and does not reach the flammable concentration range. For example, CO2, NH3, HCl, H2O, etc. can be used as a diluent gas. Ammonium phosphate, ammonium chloride, ammonium carbonate and the like can generate such incombustible gas when heated.

4. Inhibitory effect

This is a class of inhibitors that can cut off the free radical chain reaction of ignition and combustion. This kind of substance can repeatedly react with · OH to generate H2O, cut off the reaction chain of free radicals, inhibit the occurrence of oxidation reaction, so that it will not be fierce to the extent of fire, that is, it will be in a strong heat source environment, the fire will also be left after the external heat source, due to less heat and can not maintain combustion, self-extinguishing from the fire. Commonly used bromine, chlorine and other organic halogen compounds have this inhibitory effect.

5. Transfer effect

Its function is to change the mode of thermal decomposition of high polymer materials, thereby suppressing the generation of flammable gases. For example, the use of acid or alkali to produce a dehydration reaction of cellulose and then decomposed into carbon and water, rather than flammable gas, so that it can not be burned on fire. Ammonium chloride, ammonium phosphate and other flame retardants belong to this category.

6. Synergies

Here is mainly the use of flame retardants. Some compounds have no flame retardant effect or little effect when used alone, and can enhance the flame retardant effect. For example, the use of antimony trioxide and halogen compounds can greatly improve the flame retardant efficiency and reduce the total amount of flame retardant.