Flame Retardants Are The Patron Saints Of Invisibility

fire retardants (fire retardants; flame retardants), also known as flame retardants, refractory or fire retardant: functional additives that give inflammable polymers flame retardancy; According to the way of application, it can be divided into additive flame retardant and reactive flame retardant.
Additive type flame retardant is directly mixed with resin or rubber, easy to process, adapt to a wide range, is the main body of flame retardant. Reactive flame retardants are often bonded to polymer chains as monomers, which have little effect on the properties of products and have a long flame retardant effect.
According to the composition, the additive flame retardants mainly include inorganic flame retardants, halogenated flame retardants (organic chlorides and organic bromides), phosphorus flame retardants (red phosphorus, phosphate ester and halogenated phosphate ester, etc.) and nitrogen flame retardants. In addition, molybdenum compounds, tin compounds and iron compounds with smoke suppression also belong to the category of flame retardants.
Flame retardants - Flame retardants mechanism
Flame retardants play their flame retarding role by several mechanisms, such as endothermic action, covering action, chain inhibition, asphyxiation of non-flammable gas, etc. Most flame retardants achieve flame retardancy through the interaction of several mechanisms.
Endothermic action
Any combustion in a short time is limited by the release of heat, if a part of the heat released by the fire can be absorbed in a short time, then the flame temperature will be reduced, radiation to the combustion surface and the action of the gasification of combustible molecules into free radicals will be reduced, combustion reaction will be a certain degree of inhibition. Under high temperature conditions, the flame retardant has a strong endothermic reaction, absorbing part of the heat released by combustion, reducing the temperature of the combustible surface, effectively inhibiting the generation of flammable gas, prevent the spread of combustion. The flame retardancy mechanism of Al(OH)3 flame retardants is to improve the flame retardancy by increasing the heat capacity of the polymer so that it absorbs more heat before reaching the thermal decomposition temperature. This kind of flame retardant gives full play to the characteristics of large amount of heat absorption when combined with water vapor to improve its flame retardant ability.
Covering action
After adding flame retardant to combustible materials, flame retardant can form a glassy or stable foam covering layer at high temperature, isolate oxygen, with heat insulation, oxygen insulation, prevent flammable gas from escaping to the purpose of flame retardant. For example, when organic phosphorous retardants are heated, they can produce cross-linked solid substances or carbonized layers with more stable structure. On the one hand, the formation of the carbonized layer can prevent further pyrolysis of the polymer, on the other hand, it can prevent the internal thermal decomposition products from entering the gas phase to participate in the combustion process.