Special fibers generally refer to fibers with high modulus and high temperature resistance, but they are not strictly defined. In general, the generally accepted special fiber: aramid (poly benzene 2 formyl para-phenylene diamine, PPTA, Kevlar), carbon fiber, ultra-high molecular weight polyethylene (UHMWPE) fiber, polystyrene and thiazole (PBT) fiber, aromatic polyester fiber, etc.

Aramid fiber is by poly benzene 2 formyl para-phenylene diamine (PPTA) crystal solution by dry jet wet spinning process molding system, according to the molecular structure is called "aromatic polyamide fiber, the commodity is called a Kevlar fiber. Began as early as in 1968 the United States dupont, the synthesis of aromatic polyamide resin and the fiber forming technology research, in 1972, dupont has realized the poly benzene 2 formyl para-phenylene diamine fiber industrialized production, known as fiber, B size is 2000 tons/year, 1973, renamed the Kevlar fiber. Aramid fiber has excellent mechanical properties, tensile strength of 280 kg/was, modulus of 6480 kg/was (kevlar 29) and 13300 kg/was kevlar (49), elongation at break of 2.3 ~ 4.0%, the proportion of light (d = 1.44 g/c m3), and high-temperature resistance (can be used under 250 ℃).

Aramid fiber is mainly used in aircraft, rocket, missile such as aviation, aerospace, and other instruments used in composite material, and also used in automobile, shipbuilding, body armor, skis, and other areas of the application of composite materials, as well as cable, high temperature resistant filter material, etc.

Carbon fiber is made from synthetic fiber or synthetic fiber and preoxidized into non-molten fiber under tension, which is formed by sintering carbonization (or graphitization) in an inert atmosphere. The main raw material with polyacrylonitrile (PAN) fiber, viscose fiber and asphalt (Pitch). Carbon fiber technology first appeared in 1959 in the United States, in 1964 the British technology of carbon fiber has carried on the significant improvements, it built the technology in carbon fiber industry. Carbon fiber has excellent mechanical properties, tensile strength of 360-720 kg/was, modulus is 24000-30000 kg/was, elongation at break of 1.5-2.0%, high-temperature resistance (can be used in 380 ℃ or so), but slightly higher than the proportion of aramid (carbon fiber proportion of 1.76 to 1.76 g/m3) c. Carbon fiber is mainly used in aircraft, rockets, missiles, satellites and other aerospace equipment used in composite material, also can be used in the car, ship, body armor, snowboarding, fishing rod, tennis racket and so on need high strength mechanical products manufacturing.

High molecular weight polyethylene (UHMWPE) fiber manufacturing technology was developed in 1978, and the high molecular weight polyethylene production technology was studied in China in 1985. The current ultra high molecular weight polyethylene fiber (molecular weight of 1 million to 5 million) is prepared by gel spinning - ultra - high - double draft technology, which is now industrialized in China. The performance of high molecular weight polyethylene fiber of commodities is: anti-tensile strength of 2.4-3.8GPa/mm2, anti-tensile modulus 88-166gpa/mm2, breaking elongation rate of 2.7-3.6%, weight 0.97-0.98 g/c m3. But its melting point at about 150 ℃, so the temperature was below 100 ℃. Ultra high molecular weight polyethylene fiber is mainly used in the production of bulletproof clothing, parachutes, strong ropes and advanced packaging materials. It is also used to make composite materials with low temperature.