Flame retardants exert their flame retardant effects through several mechanisms, such as endothermic effect, covering effect, inhibition of chain reaction, and asphyxiation of non-combustible gases.
1. Endothermic effect
Any combustion in a short period of time the release of heat is limited, if you can in a short period of time to absorb part of the heat released by the fire, then the flame temperature will be reduced, the radiation to the combustion surface and the role of the combustible molecules have been vaporized into free radicals of heat will be reduced, the combustion will be a certain degree of inhibition.
Under high temperature conditions, the flame retardant has a strong endothermic reaction, absorbs part of the heat released by combustion, reduces the temperature of the combustible surface, effectively inhibits the generation of flammable gases, and prevents the spread of combustion.
This kind of flame retardant gives full play to its characteristics of a large number of heat absorption when combined with water vapor, and improves its own flame retardant ability.
2. The role of coverage
After the flame retardant is added to the combustible material, the flame retardant can form a glassy or stable foam coating at high temperature, isolate oxygen, have heat insulation, oxygen barrier, and prevent the escape of combustible gas, so as to achieve the purpose of flame retardant.
For example, when the organic phosphorus flame retardant is heated, it can produce a cross-linked solid substance or a carbonized layer with a more stable structure.
On the one hand, the formation of the carbonized layer can prevent the further pyrolysis of the polymer, on the other hand, it can prevent the internal thermal decomposition organisms from entering the gas phase to participate in the combustion process.