Flame retardant fiber for textile

Flame retardant fiber for textile is a kind of high temperature resistant fiber used in textile industry. The main chain or side chain of this kind of fiber contains rigid benzene ring. The high temperature resistance and flame retardancy of the fiber are closely related to the density of benzene ring, the position and linking mode of benzene ring in the molecule.

1. Linear aromatic high temperature resistant flame retardant fiber

(1) PPTA Fiber

PPTA is called aramid 1414 or para aramid in China, and Kevlar in DuPont and Twaron in Japan. It is a kind of special synthetic fiber with high strength, high modulus and high performance. At the same time, it is also an excellent high temperature resistant flame retardant fiber. Its LOI is about 30, glass transition temperature is about 345 ℃, high temperature does not melt, and decomposition temperature is up to 560 ℃. Kevlar can be used alone, more used in the field of composite materials. Although Kevlar performance is extremely superior, but the output is small, the price is expensive, mainly used in aerospace and defense industry, a small amount of protection as bulletproof clothing. Industrial production has not yet been realized in China.

(2) Poly (m-phthaloyl-m-phenylenediamine) (MPTA) fiber has become Aramid 1313 or meta aramid fiber in China. It is a kind of meta aramid fiber produced by DuPont company, and its trade name is Nomex. MPTA is prepared by dry spinning with m-phenylenediamine (MPD) and chlorine m-phenylenedicarboxylate (ICI) as monomers by interfacial polycondensation or low temperature solution polycondensation. The glass transition temperature of Nomex is about 270 ℃, the thermal decomposition temperature is as high as 430 ℃, the working time at 200 ℃ is up to 20000 h, the strength keeps 90% of the original, the strength keeps 70% of the original when it works in hot air at 260 ℃ for 1000 h, the MPIA fiber does not melt, and the LOI is about 32. Nomex can tolerate most acids, but its strength will decrease when it is exposed to strong acids or bases for a long time. Moreover, Nomex can embrittle slowly under high temperature steam, and release a small amount of combustible carbon monoxide when dispersed. Aramid 1313 has developed rapidly in China in recent years, and has realized industrial production. The "Newstar" brand produced by Yantai spandex Co., Ltd. is the best, and its annual output has exceeded 4000 tons.

(3) Aromatic fibers containing heteroatoms

The introduction of one or more specific heteroatoms into the molecular chain of aromatic fiber can further improve the reagent resistance or heat and flame retardancy of the fiber. Polyphenylene sulfide fiber (PPS) belongs to this type. Polyphenylene sulfide fiber was developed and produced by Philips oil company in 1973. When PPS resin is heated to near melting point in air, the polymer chain will stretch and cross link, and the relative molecular weight will be further improved. PPS resin can be made into staple fiber by melt spinning. Loi can reach about 35, and it can resist most chemical reagents. Its strength stability in strong acid, strong base and organic solvent is second only to that of polytetraazaethylene fiber. It has rare thermal stability. At 200 ℃ for 54 days, its breaking strength has no loss. At 260 ℃ for 48 hours, the fiber strength keeps 60% of the original strength.

(4) The introduction of heterocyclic groups into the molecular structure of aromatic fibers, limiting the extension degree of freedom of molecular conformation and increasing the covalent bond binding energy on the main chain can greatly improve the modulus, strength and heat resistance of the fibers.

① PBI PBI fiber has high insulation and good heat resistance. Its dispersion temperature is 660 ℃. It has good thermal stability and low thermal shrinkage. PBI is high temperature, smokeless and low toxicity, LOI is as high as 48. However, PBI has poor light resistance. Under the action of sunlight, the strength and relative molecular weight of PBI decrease significantly, and the stability of PBI to chemical reagents is poor. In addition, the amine monomers used in the synthesis of resin have carcinogenicity, which limits the popularization of PBI.

② Unlike PBI, PBO is not only a high temperature resistant and flame retardant fiber, but also a high strength, high modulus and high performance fiber. Its mechanical properties are even better than Kevlar. PbO was prepared by liquid crystal spinning using 2,4-diaminoresorcinol hydrochloride and terephthalic acid as monomers. The LOI of PBO is 68 and the thermal dispersion temperature is 650 ℃.

2. Graphitized carbon fiber

Carbon fiber refers to the fiber whose chemical composition of carbon element accounts for more than 90% of the total mass. According to the raw materials, carbon fiber can be divided into polyacrylonitrile based carbon fiber, pitch based carbon fiber and cellulose based carbon fiber. PAN fiber was pre oxidized in air oxidation furnace at 200-300 ℃ to form a kind of conjugated trapezoidal structure pre oxidized fiber. Then, carbon fiber was obtained by carbonization in inert gas at 1200-1600 ℃ for several minutes to several 10 minutes. Carbon fiber was graphitized in inert gas at 2000-3000 ℃ for several seconds to several 10 seconds to obtain graphitized carbon fiber. At the high temperature of 2000 ℃, the fiber forms a graphite like hexagonal crystal structure, and the more perfect the crystal structure is, the better the fiber performance is.

3. Thermosetting three-dimensional cross-linked fiber

The characteristic of the fiber is that at least one monomer in the fiber monomer has three or more functional groups, so that the fiber molecular chain can finally form a three-dimensional cross-linked structure, and the cross-linked structure has a direct impact on the high temperature resistance and flame retardancy of the fiber. Phenolic fiber and melamine formaldehyde fiber are thermosetting three-dimensional cross-linked fibers.

(1) Phenolic fiber (kynol)

Phenolic resin fiber is the first fiber with three-dimensional cross-linking structure, which breaks the traditional concept that thermosetting resin can not form fiber. It is made from novolac type thermoplastic pure linear phenolic resin with molecular weight of 300-2000 by melt spinning and cross-linking in the presence of acid and formaldehyde. Because the phenolic resin fiber is highly cross-linked and stable in chemical properties, LOI can reach about 34. The phenolic resin fiber does not dissolve and burn at high temperature. Even if it is carbonized into a glassy structure, it does not shrink. There is no alkene gas and toxic gas in the carbonization process. However, there are many defects in the application of phenolic resin fiber, such as brittle fiber, low wear resistance, strength of only 0.882-1.323 CN / dtex, poor dyeing property and easy discoloration in sunlight.

(2) Melamine formaldehyde fiber (MF)

Melamine formaldehyde fiber is commonly known as melamine fiber. Melamine and formaldehyde are condensed into a prepolymer with a certain molecular weight in a specific solvent, and then centrifugally spun and cured at high temperature. LOI is up to 37 or more. When exposed to fire, it does not shrink and does not dissolve droplets. It can basically maintain its original shape at 400 ℃. When carbonized at a higher temperature, it is basically free of toxic gas. The smoke emission is also very small. The fiber has high whiteness, stable color, good dyeability, acid and alkali resistance and most chemical reagents.

4. PTFE fiber

Polytetrafluoroethylene (PTFE) fiber is one of the earliest high temperature resistant and flame retardant fibers. Any solvent can not dissolve it, and its melting point is similar to that of the decomposition point. Therefore, it can not be formed by traditional solution or melt spinning method. The resin obtained by emulsion polymerization can be prepared by carrier spinning, film crack spinning or paste extrusion. When the long-term service temperature of PTFE is - 120-250 ℃ and the strength failure temperature is 310 ℃, the depolymerization begins when the temperature is above 390 ℃, and the LOI is as high as 95. It is the most refractory organic fiber in high oxygen environment.

5.Visil

Visil fiber is a new kind of high temperature resistant and flame retardant viscose fiber, which is a blend fiber composed of cellulose and silicate. Its short-term heat resistance temperature is 1300 ℃, long-term service temperature is 320 ℃, and LOI is about 31.

6. Other types of high temperature resistant and flame retardant fibers in recent years, several new high temperature resistant and flame retardant resin raw materials and fiber varieties have been developed in the world. In addition to excellent high temperature resistant and flame retardant properties, these new varieties are more close to or reach the level of high-performance fibers (such as PK and PEEK) in mechanical properties, and the production process is simpler than traditional high-performance fibers, The cost of finished fiber is lower