Halogen-free flame retardants are composite materials based on resin and rubber. They are a class of additives that can prevent the ignition of polymer materials or inhibit flame propagation. Among the most commonly used halogen-free flame retardants are compounds of phosphorus, bromine, chlorine, antimony, and aluminum. According to the use method, halogen-free flame retardants can be divided into two types: additive and reactive. The additive flame retardants mainly include halogenated hydrocarbons, phosphate esters, and antimony oxides, which are blended into the composite material during processing, which is relatively convenient to use. The other is a reactive flame retardant. During the preparation process, a polymerization system is added to make it compound to the polymer molecular chain through chemical reaction, so it has less impact on the performance of the composite material and has better flame retardancy. Below, I will share with you what the role of halogen-free flame retardants in the fire is, as follows:

1.Cover effect

       After adding halogen-free flame retardant to combustible materials, it can form a glassy or stable foam cover at high temperature to isolate oxygen, have the function of heat insulation, oxygen barrier, and prevent the flammable gas from escaping outward, so as to achieve the flame retardant purpose . The reason is that on the one hand, it can prevent the polymer from further pyrolysis, and on the other hand, it can prevent the internal thermal decomposition products from entering the gas phase to participate in the combustion process.

2. Inhibit the chain reaction

       According to the combustion chain reaction theory, free radicals are required to sustain combustion. Halogen-free flame retardants can act on the gas phase combustion zone, prevent the flame from spreading, reduce the flame density in the combustion zone, and reduce the combustion reaction rate until the termination. For example, the halogenated flame retardant has the same or similar evaporation temperature as the polymer decomposition temperature. When the polymer is decomposed by heat, the flame retardant also volatilizes at the same time. It can capture the free radicals in the combustion reaction, thereby preventing the flame from spreading. , So that the flame density in the combustion zone is reduced, and finally the combustion reaction speed is reduced until the termination.

3. Asphyxiating effect of non-combustible gas

       The halogen-free flame retardant decomposes unfavorable combustion gas when heated, and dilutes the concentration of combustible gas below the lower combustion limit, dilutes the oxygen concentration in the combustion zone, prevents the combustion from continuing, and achieves the flame retardant effect.