Yinyuan New Materials: Different Flame Retardant Mechanisms

Becoming a safety guard to restrain fires is not an easy task, flame retardants must have strong capabilities. Combustion requires three elements - combustibles, comburent, like oxygen and a fire source. The combustion process includes heating, decomposition, ignition, combustion, and spread. When any of these elements are removed or the combustion process is controlled in the budding stage of heating and decomposition, fire can be effectively prevented.

Different types of flame retardants have different tricks in preventing flame combustion:

Ÿ  Some absorb heat to prevent the generation of combustible gases;

Ÿ  Some form a dense covering layer on the surface of the combustible material to isolate the contact between the combustible material and oxygen;

Ÿ  Some capture free radicals involved in the combustion reaction to achieve the purpose of inhibiting free radical chain reactions;

Ÿ  Others produce non-combustible gases to dilute oxygen, thereby achieving the effect of slowing down the combustion rate.

Inorganic flame retardant Al(OH)₃ decomposes after being heated to 200°C, releasing water of crystallization, which evaporates into water vapor when heated. This series of processes will absorb a lot of heat, reduce the temperature of the material surface and the flame area, and slow down the speed of thermal cracking reaction. In addition, the water vapor produced by crystal water can also reduce the oxygen concentration and further suppress the spread of fire.

Phosphorus flame retardants become more stable cross-linked solid substances or carbonized layers when heated, like a solid armor that wraps around combustibles, which can prevent further thermal decomposition of materials and prevent combustible gases from overflowing and continuing to burn.

The evaporation temperature of bromine flame retardants is the same or similar to the decomposition temperature of polymer materials. When polymer materials are thermally decomposed, bromine flame retardants will also volatilize and enter the gas-phase combustion zone with thermal decomposition products. The flame retardant can quickly capture free radicals in the gas-phase combustion zone, inhibit free radical chain reactions, prevent flame propagation, and eventually slow down the combustion reaction until it stops.

In summary, each flame retardant has its own unique secret recipe.