The working principle of halogen-free flame retardants

Halogen free flame retardants are widely used in halogenated polymers or flame retardant mixtures. There are various types of halogen-free flame retardants, which can be divided into additive halogen-free flame retardants and reactive halogen-free flame retardants according to their usage methods. Additive flame retardants include halogenated hydrocarbons, phosphate esters, metal borides, hydrated metal oxides, metal oxides, and expansion flame retardants. The following introduces the functions of halogen-free flame retardants:
1. Coverage
When flame retardant is added to combustible materials, the flame retardant can form a glassy or stable foam covering layer under high temperature to isolate oxygen, and has the functions of heat insulation, oxygen isolation, and preventing combustible gas from escaping out, so as to achieve flame retardant effect.
2. Heat absorption
The amount of heat released by any combustion in a short period of time is limited. If a portion of the heat released by the ignition source can be absorbed in a short period of time, the flame temperature will decrease, and the heat that radiates to the combustion surface and acts on the vaporized combustible molecules to decompose into free radicals will be reduced, and the combustion reaction will be inhibited to a certain extent. Under high temperature conditions, flame retardants have a strong endothermic reaction, absorbing some of the heat released during combustion, reducing the surface temperature of combustible materials, effectively suppressing the production of combustible gases, and preventing combustion diffusion.
3. Non combustible gas suffocation
When flame retardants are heated, they will decompose into non combustible gases and dilute the concentration of combustible gases decomposed from combustibles to below the lower limit of combustion. At the same time, it can also dilute the oxygen concentration in the combustion zone, prevent combustion from continuing, and achieve flame retardant effect.
4. Inhibition of chain reaction
According to the chain reaction theory of combustion, free radicals are required to maintain combustion. Flame retardants can act on the gas-phase combustion zone, capturing free radicals in the combustion reaction, thereby preventing flame spread, reducing flame density in the combustion zone, and slowing down the combustion reaction rate until it terminates.
Among halogen-free flame retardants, environmentally friendly flame retardants are also excellent, with better halogen-free flame retardancy and environmental performance. At present, halogen-free flame retardants for smoke suppressants mainly include organic and inorganic, halogen-free and halogen-free. Organic flame retardants are halogen-free flame retardants represented by compounds, red phosphorus, nitrogen, and bromine, while inorganic flame retardants mainly include flame retardants such as aluminum hydroxide, magnesium hydroxide, antimony trioxide, silicon, etc. Generally speaking, organic flame retardants have good affinity in plastics. Brominated halogen-free flame retardants have absolute advantages in organic flame retardant systems. It has been criticized for environmental issues, but it is difficult to replace other halogen-free flame retardant systems.

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