Combustion of polymers is a very complex and violent oxidation reaction. The combustion process is that under the continuous heating of the external heat source, the polymer first undergoes a free radical chain degradation reaction with oxygen in the air, and a part of the heat is released to further aggravate the degrading polymer and generate more flammable gases. , making the combustion more intense.

There are two ways to flame retardant plastics, one is to chemically introduce flame retardant elements or atomic groups containing new flame retardant elements into the molecular structure of plastics; the other method is to add flame retardant elements to plastics containing resistance. Compounds of flammable elements. The flame retardant substances used in the former method are called reactive flame retardants, and the substances used in the latter method are called additive flame retardants.

At present, most of the flame retardants used in plastics are additive flame retardants, while reactive flame retardants are mainly used in thermosetting resins such as epoxy resin and polyurethane. The main function of flame retardants is to interfere with the three basic elements of maintaining combustion: oxygen, heat and combustibles. Generally, it can be achieved in the following ways.

1. Flame retardants can produce heavier non-combustible gas or boiling point liquid, covering the plastic surface, blocking the connection between oxidation and combustibles.

2. Reduce the surface temperature of the polymer through the endothermic decomposition or endothermic sublimation of the flame retardant.

3. The flame retardant produces a large amount of non-combustible gas, and the flammable gas concentration and oxygen concentration in the burning area are discussed.

4. The flame retardant captures free radicals and interrupts the chain oxidation reaction.