What is the role of flame retardants?

Flame retardant is a chemical additive that plays an important role in industry, life and other fields. It can suppress the flammability of materials and achieve the ideal flame retardancy of materials. The safety of people's lives and property also brings a guarantee. The specific role of flame retardants includes the following aspects.

1. Asphyxiation of non-combustible gas
The flame retardant will decompose non-combustible gas after being heated, and the concentration of combustible gas decomposed by combustible materials will be diluted to the lower combustion limit. It will also dilute the oxygen concentration in the combustion range, successfully hindering the spread of fire.

2. Endothermic effect
The heat released by any combustion in a short time is limited. If a part of the heat released by the fire source can be absorbed in a short time, the flame temperature will be reduced, radiating to the combustion surface and acting on the gas that has been vaporized. The heat of the cracking of combustible molecules into free radicals will be reduced, and the combustion reaction will be suppressed to a certain extent. Under high temperature conditions, the flame retardant has a strong endothermic reaction, absorbs part of the heat emitted by the combustion, reduces the temperature of the surface of the combustibles, effectively suppresses the generation of combustible gases, and prevents the spread of combustion. The flame retardant mechanism of Al (OH) 3 flame retardant is to increase the heat capacity of the polymer so that it can absorb more heat before reaching the thermal decomposition temperature, thereby improving its flame retardant performance. This type of flame retardant fully exerts its characteristics of absorbing a large amount of heat when combined with water vapor, and improves its own flame retardant ability.

3. The suffocation of non-combustible gas
Flame retardant decomposes non-combustible gas when it is heated, and dilutes the concentration of combustible gas decomposed by combustibles below the lower combustion limit. At the same time, it also has the effect of diluting the oxygen concentration in the combustion zone, preventing the continuation of combustion and achieving the effect of flame retardancy.

4. Inhibit chain reaction
According to the chain reaction theory of combustion, it is free radicals that 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, thereby preventing the flame from spreading, reducing the flame density in the combustion zone, and ultimately reducing the combustion reaction rate until it terminates. If the halogen-containing flame retardant, its evaporation temperature and polymer decomposition temperature are the same or similar, when the polymer is thermally decomposed, the flame retardant also volatilizes at the same time. At this time, the halogen-containing flame retardant and the thermal decomposition products are in the gas-phase combustion zone at the same time, and the halogen can capture the free radicals in the combustion reaction, thereby preventing the spread of the flame, reducing the flame density in the combustion zone, and finally reducing the combustion reaction rate until the termination .