Halogen free flame retardants, halogenated polymers or flame retardant mixtures have been widely used. 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, expansion flame retardants, etc.
The following introduces the function of halogen-free flame retardants:
1. Coverage Area
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 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 radiated to the combustion surface and acting on the vaporized combustible molecules to decompose into free radicals will be reduced, which will suppress the combustion reaction 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 combustibles, 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 combustion limit. 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. Inhibit 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 aluminum hydroxide, magnesium hydroxide, antimony trioxide, silicon, and other flame retardants. Generally speaking, organic flame retardants have good affinity in plastics. Brominated halogen-free flame retardants have an absolute advantage in organic flame retardant systems. Highly criticized for environmental issues, but difficult to replace other halogen-free flame retardant systems.
