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The principle of flame retardant is introduced in detail
2021-01-31

What is the principle of flame retardant that we usually use? Specific flame retardant principle we here to give you a detailed introduction, specific details see below.

Flame retardants exert their flame retardancy through several mechanisms, such as endothermic effect, covering effect, inhibition of chain reaction, asphyxiation effect of non combustible gas, etc. Most of the flame retardants achieve the purpose of flame retardancy through several mechanisms.

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1. Endothermic effect

The heat released by any combustion in a short time is limited. If part of the heat released by the fire source can be absorbed in a short time, the flame temperature will be reduced, the heat radiated to the combustion surface and acting on the cracking of vaporized combustible molecules into free radicals will be reduced, and the combustion reaction will be inhibited to a certain extent. At high temperature, the flame retardant has a strong endothermic reaction, which can absorb part of the heat released by combustion, reduce the temperature of the surface of the fuel, effectively inhibit the generation of combustible gas and prevent the spread of combustion. The flame retardant mechanism of Al (OH) 3 flame retardant is to increase the heat capacity of the polymer and make it absorb more heat before reaching the thermal decomposition temperature, so as to improve its flame retardant performance. This kind of flame retardants give full play to their heat absorption characteristics when combined with water vapor, and improve their own flame retardancy.

2. Coverage

After adding flame retardants in combustible materials, flame retardant can form glass or stable foam covering at high temperature, and isolate oxygen, which has the function of heat insulation, oxygen isolation and preventing flammable gas from escaping outward, so as to achieve the purpose of flame retardancy. For example, when the flame retardant is heated, it can produce more stable cross-linked solid substance or carbonized layer. On the one hand, the formation of carbonization layer can prevent the polymer from further pyrolysis, on the other hand, it can prevent the thermal decomposition products from entering the gas phase to participate in the combustion process.

3. Inhibition chain reaction

According to the chain reaction theory of combustion, free radicals are needed to maintain combustion. The flame retardant can act on the gas-phase combustion zone to capture the free radicals in the combustion reaction, so as to prevent the spread of flame, reduce the flame density in the combustion zone, and finally reduce the combustion reaction speed until the end. For example, the evaporation temperature of halogen-containing flame retardant is the same as or close to the decomposition temperature of polymer. When the polymer is decomposed by heat, the flame retardant also volatilizes. At this time, halogen containing flame retardant and thermal decomposition products are in the gas phase combustion zone at the same time, halogen can capture the free radicals in the combustion reaction, so as to prevent the spread of flame, reduce the flame density in the combustion zone, and finally reduce the combustion reaction speed until the end.

4. Asphyxiation of incombustible gas

When the flame retardant is heated, it decomposes into incombustible gas and dilutes the concentration of combustible gas decomposed from combustible to below the lower limit of combustion. At the same time, it can also dilute the oxygen concentration in the combustion zone to prevent the combustion and achieve the flame retardant effect