Flame retardants work through four main effects

(1) Cooling effect: Some flame retardants absorb the heat released when plastics burn, lowering the temperature of the burning plastic and preventing it from further degrading or cracking, thus interrupting the source of flammable gases and extinguishing the flame, such as organic phosphorus-nitrogen intumescent flame retardants;

(2) Isolation effect: During combustion, they produce non-flammable gases or foam layers or form a liquid or solid cover layer that stops the combustion process due to the lack of oxygen, such as halogenated flame retardants, intumescent graphite, and polyols and polyvinyl alcohol;

(3) Free radical elimination effect: During combustion, they eliminate free radicals O· and OH· produced by cracking or thermal decomposition, interrupting the chain reaction of combustion and cutting off the source of flammable gases, such as halogenated flame retardants;

(4) Dilution effect: During combustion, they release inert gases that dilute the concentration of flammable gases and oxygen in the combustion area, preventing combustion from continuing, such as boron compounds and molybdenum compounds.