(1) Bromine-based flame retardants Bromine-containing flame retardants include aliphatic, cycloaliphatic, aromatic, and aromatic-aliphatic bromine-containing compounds. These flame retardants have high flame retardancy and their flame retardant effect is chlorine. Double the flame retardant, relatively small amount, has almost no effect on the mechanical properties of the composite material, and can significantly reduce the content of hydrogen halide in the gas. Moreover, this type of flame retardant has good compatibility with the matrix resin, even if it is harsh No spray appeared under the conditions. Bromine-based flame retardant is the most important and effective one among halogen-containing flame retardants. It has high flame resistance, low addition amount, and has little impact on the processing and use characteristics of products. The properties of aliphatic, cycloaliphatic, and aromatic bromides and the organic part of the bromide monomer have a great influence on the fire extinguishing performance of the resin. Aromatic bromide is the most heat-resistant and least flammable. The order of flame retardant effect is generally aliphatic> alicyclic> aromatic, but the thermal performance is just the opposite, that is, the aliphatic is the worst and the aromatic is the best. The most commonly used aliphatic bromides are tetrabromoethane, tetrabromomethane, tetrabromobutane and the like. Due to poor thermal stability, poor weather resistance and durability, it has been replaced by alicyclic and aromatic bromides. Alicyclic bromides are commonly used hexabromocyclohexadecane, tris (dibromopropyl) isocyanate, and aromatic bromides commonly used are tetrabromobisphenol A, decabromodiphenyl ether, tetrabromophthalic anhydride, etc. . Bromine flame retardants have the ability to reduce the concentration of OH ˙ radicals. The bromine-containing flame retardant is thermally decomposed in the flame to release the free radical Br ˙, which reacts with the combustion products to form HBr. HBr reacts with the highly reactive OH ， to form Br ˙. This repeated cycle action continuously Consumption reduces the concentration of OH ˙ and thereby inhibits the progress of the combustion reaction. At the same time, HBr is heavier than air and covers the combustion surface, which greatly reduces the contact area between the resin and the outside world. In this way, Br ˙ radicals become "negative catalysts" for the chain reaction in the combustion process. This negative catalyst is a halogen radical This effect is most specific, especially bromine.

(2) Chlorine flame retardants Due to their cheap personality, chlorine flame retardants are still widely used flame retardants. Chlorinated paraffin with the highest chlorine content is an important flame retardant in the industry. Due to its poor thermal stability, it is only suitable for composite materials with a processing temperature below 200 ℃, thermal stability of chlorinated alicyclic hydrocarbons and tetrachlorophthalic anhydride Higher, often used as a flame retardant for unsaturated resins.

(3) Phosphorous flame retardants and organic phosphides are additive flame retardants. The metaphosphoric acid generated during the combustion of such flame retardants can form stable polymers, covering the surface of composite materials to isolate oxygen and combustible materials, and Flame retardant effect, its flame retardant effect is better than bromide. To achieve the same flame retardant effect, the amount of bromide is 4-7 times that of phosphide. This type of flame retardant mainly includes phosphorus (phosphonate) esters, halogen-containing phosphate esters, and phosphorus halides. They are widely used in epoxy resins, phenolic resins, polyesters, polycarbonates, polyurethanes, polyvinyl chloride, polyethylene, Polypropylene, ABS, etc.

(4) Inorganic flame retardants Halogen-free flame retardants are a class of flame retardants classified according to their chemical structure habits, including antimony oxide, aluminum hydroxide, magnesium hydroxide, and zinc borate.