1. Flame Retardant-Cooling Effect

Some flame retardants can absorb the heat released by plastics during combustion, reduce the temperature of burning plastics, prevent it from continuing to degrade or crack, interrupt the source of flammable gases, and extinguish the flame, such as organic phosphorus nitrogen intumescent flame retardant; for example, borax has 10 molecules of crystalline water, which takes 141.8 kJ/mol of heat due to its heat absorption. The degree of increase was inhibited, resulting in flame retardant effect. The flame retardant effect of alumina hydrate is also due to the endothermic effect of thermal dehydration. In addition, the droplets often produced in the pyrolysis of some thermoplastic polymers can also play a certain flame retardant effect because they can move the reaction heat away from the combustion zone.

2. Smoke suppression-isolation effect

During the combustion process, a non flammable gas or foam layer is formed, or a liquid or solid covering layer is formed, so that the combustion process is stopped due to the addition of oxygen, such as halogen flame retardants, expanded graphite, polyols and polyvinyl alcohol.

The effect of covering effect is to form a stable covering layer at high temperature, or to decompose and form foamed material, covering the surface of polymer material, so that the heat generated by combustion can hardly be introduced into the interior of the material, so that the combustible gas generated by thermal decomposition of polymer materials is difficult to escape, and the air is separated from the material, thereby inhibiting the pyrolysis of materials and achieving the effect of flame retardance. 。 Such as phosphate compounds and fire-proof foaming coatings can play a role according to this mechanism.

3. Heat Dissipation-Elimination of Free Radicals

Free radicals O and OH produced by pyrolysis or pyrolysis can be eliminated in the combustion process, which can cut off the source of combustible gases, such as halogen flame retardants. The combustion of polymers is mainly free radical chain reaction. Some substances can capture the active intermediates of combustion reaction, such as HO, H, O, HOO, etc., and inhibit free radical chain reaction, so that the combustion rate can be reduced until the flame extinguishes. The common organic halogen compounds such as bromine and chlorine have this inhibitory effect.

4. Drop-proof-dilution effect

During combustion, inert gases can be released, and the concentration of combustible gases and oxygen in the combustion zone can be diluted, so that combustion can not proceed, such as boron compounds and molybdenum compounds.

This kind of material can produce a large number of non-combustible gases during thermal decomposition, so that the combustible gases produced by polymer materials and oxygen in the air can not reach the combustible concentration range, thus preventing the ignition and combustion of polymer materials. Carbon dioxide, NH3, HCl and hydrogen peroxide can be used as diluent gases. This kind of nonflammable gas can be produced when ammonium phosphate, ammonium chloride and ammonium carbonate are heated.