Discussion on the flame retardant mechanism and performance of flame retardants

The combustion reaction generally consists of three basic elements: combustibles, oxygen, and a certain temperature, all of which are indispensable. The effective mechanism of flame retardants is to suppress the production of one or more elements during the combustion process of materials, in order to prevent or slow down combustion. The specific flame retardant mechanism of each flame retardant is different, but the basic principle of flame retardancy is the same. It reduces the production of combustible gases during thermal decomposition and hinders the basic reactions during gas combustion, absorbs heat from the combustion domain, dilutes and isolates air, and also has a certain effect on preventing combustion. The flame retardant effect of flame retardants includes the following main processes.
1.1 Heat absorption cooling
During the heating process, certain flame retardants may undergo endothermic dehydration, phase transition, decomposition, and other endothermic reactions in compounds containing flame retardant elements, reducing the temperature of the polymer surface and combustion area, thereby slowing down the thermal decomposition rate of the polymer and achieving flame retardant effects.
1.2 Gas phase dilution
During the combustion process, materials will produce a large amount of combustible gases, such as carbon monoxide. The presence of flame retardants can generate a large amount of non combustible gases, effectively diluting combustible gases and air, thereby achieving the flame retardant effect of the material.
1.3 Forming an insulation layer
Some flame retardant materials (such as phosphoric acid and boric acid) will melt when heated, forming a glassy thin film on the surface of the material, which hinders the supply of oxygen and also serves as insulation, reducing the release of combustible gases and producing flame retardants. Flame retardant effect.
Termination of free radical chain reaction
During the combustion process of polymers, a large number of free radicals are generated to accelerate gas-phase combustion reactions. If we can find ways to capture and eliminate these free radicals, we can control combustion and achieve flame retardant effects. The speed of gas-phase combustion reaction is closely related to the concentration of free radicals HO · and H · generated during the combustion process. The main function of gas-phase flame retardants is to convert these high-energy free radicals into stable free radicals, suppress the combustion process, and achieve flame retardancy. Free radicals in contact with the surface of dust particles may lose their activity. The following reactions can occur on the surface of dust particles: H ·+O2 · - H2O2, which generates a large amount of free radicals HO2 with much lower activity than H ·, HO ·, etc. on the surface of dust particles, thereby achieving the goal of suppressing combustion.
Overall, flame retardants mainly achieve material flame retardancy through methods such as endothermic cooling, dilution, formation of insulation layer, and termination of free radical chain reaction. The first three are physical effects, while the latter is chemical effects. Physical effects include heat absorption, dilution of combustible materials, isolation of air, etc; Chemical reactions include carbonization, elimination of free radicals, and phosphorylation.
Common flame retardant insulation tapes include: Mara tape, non-woven barrier tape, rubber barrier tape, polyimide tape, high-temperature tape, etc.