Flame retardant, a kind of additive with special function that can make the polymer that is easy to burn become not easy to burn. It is mainly designed for polymer materials in terms of flame retardancy, and is designed to play a flame retardant role through such mechanisms as heat absorption, coverage, inhibition of chain reactions, and asphyxiation by non-flammable gases. Most flame retardants rely on several of these mechanisms to work together to achieve the goal of flame retardancy.
Role of Flame Retardant
1. Heat absorption:
If a part of the heat released by the fire source can be absorbed in a short period of time, the flame temperature will be lowered, the heat radiated to the burning surface and used to crack the already gasified combustible molecules into free radicals will become burnt, and the combustion reaction can be suppressed to a certain extent. At high temperature, the flame retardant will have a strong heat absorption reaction, which can absorb part of the heat released by combustion, so that the temperature of the surface of the combustible material will drop, effectively preventing the production of flammable gases, and preventing the combustion from continuing to spread.The flame retardant principle 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 temperature of thermal decomposition, which will make its flame retardant performance better. . This kind of flame retardant makes full use of the feature of absorbing large amount of heat when combining with water vapour to enhance its flame retardant ability.
2. Covering effect:
which can play the role of heat insulation, oxygen insulation, and preventing combustible gases from running out of the room, so that the purpose of flame retardant can be achieved. Like organophosphorus flame retardants, when heated, can produce a more stable structure of cross-linked solid material or carbonised layer. After the formation of the carbonisation layer, on the one hand, it can prevent the polymer from continuing thermal decomposition, and on the other hand.
3.Inhibition of chain reaction
Flame retardants can play a role in the gas-phase combustion zone, capture the free radicals in the combustion reaction, which can prevent the flame from spreading, so that the flame density in the combustion zone becomes smaller, and finally slow down the combustion reaction until it stops. For example, the evaporation temperature of halogen-containing flame retardants is similar to the decomposition temperature of polymers, and when polymers are decomposed by heat, the flame retardants will also be volatilised together. At this time, halogen-containing flame retardants and thermal decomposition products are in the gas-phase combustion zone, halogens will be able to capture the free radicals in the combustion reaction, the chain reaction of combustion to interfere.
4. Asphyxiating effect of non-flammable gas
The flame retardant will decompose the incombustible gases when it is heated, and reduce the concentration of the combustible gases decomposed from the combustible materials to below the lower limit of combustion. And it also dilutes the oxygen concentration in the combustion zone, preventing the combustion from continuing, thus acting as a flame retardant. Most polymers are made up of these elements, carbon and hydrogen, and are particularly flammable. During combustion, which is a very complex free radical chain reaction process, a lot of heat energy is released, which not only causes immediate damage, but also makes the fire get bigger very quickly.
