Flame retardants are used to improve the flame resistance of molecular materials, increase the burning point of molecular materials, or reduce the burning speed of materials, thereby increasing rescue time, saving lives and reducing losses.
According to the structure, flame retardants can be divided into macromolecular polymerization and small molecule flame retardants; according to the method of use, they can be divided into additive flame retardants and reactive flame retardants; according to the material Whether it contains halogen or not, it can be divided into halogen flame retardants and halogen-free flame retardants. Additive flame retardants are mostly used in thermoplastic polymer materials, and do not chemically react with other components in the material, and only physically exist in polymer materials. Reactive flame retardants are mostly used in thermosetting polymer materials, participate in the chemical reaction of synthetic polymer materials, and become the structural units of polymer materials.
When the polymer material is ignited by an open flame, it will undergo a violent oxidation reaction and release a large number of hydroxyl groups. Because the hydroxyl group is very active, it is easy to combine with other substances to form water and other organic substances. Other organic matter and oxygen are further combined to undergo decomposition reactions to form new organic matter. In this series of cyclic reactions, combustion continues.
How do flame retardants work in this process?
The principle of flame retardant can be summarized as:
1. Flame retardant is achieved by absorbing heat. For example, the inorganic flame retardant aluminum hydroxide decomposes at high temperature, releases crystal water, and the crystal water evaporates into water vapor. This process absorbs a large amount of heat, reduces the temperature of the material surface, and performs flame retardancy.
2. By producing non-combustible gas to dilute oxygen and slow down the burning speed, such as aluminum hydroxide flame retardant, the water vapor generated can reduce the concentration of oxygen around the material and inhibit the spread of fire.
3. Form a dense covering layer on the surface of the material to insulate the material from contact with oxygen, such as phosphorus-based flame retardants, which will become more stable cross-linked solid substances or carbonized under high temperature conditions The layer wraps around the material, preventing it from continuing to burn.
4. Capture free radicals participating in combustion reactions and inhibit free radical chain reactions, such as bromine flame retardants. Under high temperature conditions, when polymer materials are thermally decomposed, bromine flame retardants and thermal decomposition products simultaneously Enter the gas phase combustion zone, capture the free radicals in the gas phase combustion zone, inhibit the chain reaction of free radicals, thereby preventing the flame from spreading.
Tag:   flame retardant
