Explanation

It is prepared by condensation of terephthalic acid or terephthaloyl chloride with p-phenylenediamine and spinning. These fibers belong to special synthetic fiber with high strength and high modulus. Some common commercial brands include Kevlar, Twaron, and Terlon, with representative varieties including Kevlar29, Kevlar49, Kevlar129, Kevlar149, and Twaron. These fibers show excellent heat resistance. Their glass transition temperature is above 240 ° C, thermal decomposition temperature is between 500 ° C and 570 ° C, and the maximum use temperature can reach 250 ° C. They have excellent impact strength and impact absorption, so they are used in composite materials to provide excellent high-speed bullet protection. These fibers have good resistance to acid, alkali, organic solvents and corrosion of seawater. Their free length of cable (i.e. the length lost due to fracture) is 7 times longer than that of wire with the same diameter in air and 26 times longer in water, and has excellent wear resistance, but slightly poor fatigue resistance. The preparation methods of these fibers mainly include pre polycondensation of p-phenylenediamine and p-benzoyl chloride in low temperature solution in strong polar solvent (such as N-methylpyrrolidone) and continuous postpolymerization through twin-screw, then washing and drying the synthesis, finally dissolving the polymer powder in smoke like concentrated sulfuric acid for dry jet wet spinning. To prepare high modulus fibers, high-temperature tension post-treatment is usually performed. Terlon uses wet spinning and post drawing processes. These fibers are widely used to prepare the framework materials of rubber products such as tires, tapes and rubber hoses, as well as composite materials of thermosetting and thermoplastic resin, optical cable reinforcement cores, bulletproof vests, rocket engine shells, high-speed centrifugal cylinders, high-pressure containers, bulletproof helmets, tank composite armor, missile launchers, honeycomb structural materials, train brake shoes, automobile brake pads, radial tires, high-pressure hoses Streamlined structural materials for aircraft and ships, tennis rackets, mining belts, automobile clutches, wear resisting materials for agricultural machinery, fireproof and thermal insulation clothing for metallurgical industry and weld, trumpet paper trays, rowing and buildings, air self-supporting roof materials for sports fields, etc.

Classification