Synthetic fiber combustion and flame retardant mechanism

Many types of synthetic fibers, combustion performance varies. Polyester fiber generates a lot of flammable substances, heat and smoke when it is decomposed by heat. In the initial stage of heating, the intramolecular attack of -OH in the molecular chain through-OH at the chain end or the formation of cyclic oligomers by cross-linking generates carboxylic acid and vinyl ester through the intramolecular beta-H transfer process Phthalic acid by decarboxylation to generate benzoic acid, anhydride and carbon dioxide or benzene, vinyl ester chain occurs after the polymerization reaction and the chain exfoliation process cycloolefin-like cross-linked structure, but also can be further degraded directly to generate small molecules Ketones, carbon monoxide, acetaldehyde, anhydride, etc., may still produce lively free radicals.
      Acrylic fiber is a flammable fiber, easy to heat combustion. Acrylic burning is a cyclic process. At low temperatures, acrylics cyclodely decompose to produce ladder-shaped heterocyclic compounds. These compounds are cleaved at high temperatures. OH · and H · radicals, radicals further initiate chain scission reaction and release Flammable volatile gases, these gases in the fire under the action of oxygen, generating HCN, CO, CO2, NH3 and other toxic fumes. The heat released during combustion, in addition to some of the emission, will further exacerbate fiber cracking, so that the combustion process can be recycled and continued.
       Nylon fiber in the fire burning relatively slow, strong contraction of the fiber, easy to melt dripping, and the combustion process is easy to self-extinguish, mainly due to the nylon melt temperature and ignition temperature difference between the larger reason. However, the nylon fiber melts and drips, which easily causes the fire to spread in other flammable materials, thereby causing even greater damage. Because of its lower melting temperature and lower viscosity after melting, the heat generated during combustion is sufficient to melt the fiber, so nylon fibers tend to ignite more than many natural fibers. Although nylon fibers shrink, melt, and drop off and self-extinguish, polyamide fibers tend to burn more easily when they are blended or interwoven with other non-thermoplastic fibers due to their non-thermoplastic nature. Polyester is the case.
       Polyamide fiber macromolecules contain oxygen, nitrogen and other heteroatoms in the main chain. When pyrolysis occurs, various products are formed due to the breaking of different bonds, and the cracking is complicated. Under vacuum condition, the polyamide mainly decomposes above 300 ℃ to produce non-volatile products and some volatile products. The volatile products are mainly CO 2, CO, water, ethanol, benzene, cyclopentanone, ammonia and other aliphatic, aromatic carbon Hydrogen compounds and saturated, unsaturated compounds and so on.
       Polypropylene fiber is flammable fiber, it is not easy to carbonize when it is burned, all decompose into flammable gas, and a large amount of heat is released when the gas is burned, which prompts the combustion reaction to proceed rapidly.
        Different types of synthetic fibers, the flame retardant mechanism is also different. Polyester fabric flame retardants are mostly halogen and phosphorus flame retardants. Halogen-based flame retardants are mainly formed by thermal decomposition of flame retardants to generate halogen-containing gases such as hydrogen halides. On the one hand, they capture active free radicals in the gas phase. On the other hand, due to the relatively high density of the halogen-containing gas, the generated gas can cover In the combustion of the surface, to some extent play a role in isolating oxygen and combustion area contact. Brominated flame retardants are more effective than chlorine. Antimony compounds and halogen flame retardant synergistic effect. Phosphorus flame retardants have a good flame retardant effect on synthetic fibers containing carbon and oxygen, and are mainly used to reduce the amount of combustible gas produced by promoting the formation of carbon into polymers, thereby contributing to flame retardancy in the coacervates. Phosphorus flame retardant modified flame-retardant polyester fiber combustion, the amorphous carbon generated on the combustion surface can effectively isolate the combustion surface contact with oxygen and heat, while the decomposition of phosphoric acid to absorb heat, but also to a certain extent, inhibit Polyester degradation reaction. Most of the flame retardant acrylic fiber is the use of phosphorus and halogen as the main flame retardant components, its flame retardant and the application of similar on the polyester. Polyamide fiber flame retardant is mainly through two mechanisms, first, condensation phase flame retardant, through the promotion of polyester amine combustion process increases the amount of carbon, reducing the generation of flammable gases; the second is through the vapor phase capture mechanism, After the flame retardant decomposition and oxygen in the air combine to reduce the formation of lively free radicals to achieve the purpose of flame retardant. Flame retardant polypropylene fiber is mainly through the halogen flame retardant system and the synergistic effect of the system to inhibit the combustion reaction of the gas, the role of the flame retardant condensate phase in the polypropylene less used, because polypropylene is not easy to carbonized by thermal decomposition, all decomposed into flammable gas .

Flame-retardant fabrics in the prevention of fire has a good protective effect, fire-retardant overalls can effectively reduce the fire and sputter metal droplets on the human body injury - YuLong Safety