Why do flame retardants prevent burning?

1. Produce a gas that smothers the flame. Such as antimony trioxide, it in PVC due to the combustion of HCL reaction to produce a smothering gas, that is, antimony nitrogen oxide.
2. Absorb the heat generated during combustion and play the role of cooling and slowing down the combustion rate. Like aluminum hydroxide,
Its molecules contain up to 34% of chemically associated water, which remains stable at the processing temperatures of most plastics but begins to break down above 200℃, releasing water vapor. And for every gram of aluminum hydroxide it breaks down, it absorbs 36 kilocalres.
3. Provide a coating that is insulated from oxygen. Such as phosphate ester flame retardant combustion of phosphide is the coating of oxygen insulation.
4. Generate free radicals that react with plastics and act as flame retardants. Their reaction products with plastics have very poor combustion properties.
Flame retardants can be divided into additive type and reactive type according to different methods of use. Additive flame retardants act as flame retardants mainly by adding flame retardants to combustible materials. Reactive flame retardants introduce flame retardant groups into polymer materials through chemical reactions, so as to improve the fire resistance of materials, prevent materials from being ignited and inhibit the spread of flame. Among the types of flame retardants, additive flame retardants are dominant, with a relatively wide range of use, accounting for about 85% of flame retardants, and reactive flame retardants only account for 15%.