Poly (p-phenylene terephthalamide), abbreviated as PPTA, is the first company in the United States to develop poly (m-phenylene terephthalamide) (Nomex) fiber, and successfully developed poly (p-phenylene terephthalamide) (Kevlar-29) and poly (p-phenylene terephthalamide) (Kevlar-49) fibers at 1972. 1979 the consumption of aramid fiber in the United States is 7000 tons. Dupont has three major Kevlar fiber manufacturers, namely Richmond factory in the United States, with an annual production capacity of 20,000 tons; The Maytang factory in the UK has an annual production capacity of 7,000 tons; Toray DuPont's Donghai plant in Japan has an annual production capacity of 25,000 tons.
After the patent dispute between Aksu and DuPont was settled, Aksu actively developed aramid Twaron fiber and built 5000 tons of production facilities. It is planned to expand to 7000 tons in 1992. The company also plans to cooperate with Sumitomo Chemical Company to build an aramid fiber factory in Japan. Teijin company of Japan produces Technora aramid fiber in Songshan factory, and the company is going to cooperate with Hearst company of Germany to produce aramid fiber in Germany. The output of poly (p-phenylene terephthalamide) fiber in the world is about 60,000 tons. 1. Resin production
In a polymerization kettle filled with N- methylpyrrolidone, aluminum chloride (1.2 ~ 65438+ 0.8% of the feeding amount) and pyrrole (pyrrole/p-phenylenediamine = 0.6 ~ 1.2 mol) are added, then p-phenylenediamine is added, and after dissolution, terephthaloyl chloride powder (p-phenylenediamine) is added in two steps.
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Kevlar fiber is made of poly (p-phenylene terephthalamide) (PPTA) coating. PPTA is the product of condensation reaction of terephthalamide and phthaloyl chloride. PPTA was dissolved in hot concentrated sulfuric acid until the liquid crystal solid concentration reached 20% by weight. PPTA- sulfuric acid solution was sprayed into the coagulation bath by dry spinning (dry spraying-wet spinning). Then, the fibers were neutralized with an aqueous solution of sodium hydroxide, followed by water washing and drying to manufacture Kevlar fibers. 1. resin characteristics
Intrinsic viscosity ≥4.5
Ash content ≤500ppm
Light yellow
2. Fiber characteristics
Precursor heat treatment line
Tensile strength 2.8Gpa 2.8GPa
Elongation 5.76% 3.5%
Elastic modulus 5 1 ~ 64 GPA ≥ 96 GPA
Relative density 1.44 1.45
3. Thermal characteristics
Poly (p-phenylene terephthalamide) has the characteristics of ultra-high strength, ultra-high modulus, high temperature resistance and low density. The thermal weight loss of its precursor and heat-treated yarn is listed in the table. Aramid fiber with high strength, high modulus and low density will continue to develop towards ultra-high strength, ultra-high modulus and low density. As far as polymer preparation is concerned, continuous extrusion polymerization is the development direction, but the problem of molecular weight control needs to be solved. How to make polymers with uniform molecular weight distribution is still a problem to be solved. In addition, it is urgent to reduce the cost of raw materials and fiber prices. Only by lowering the price and improving the quality can we be more competitive.
In the table, the aramid fiber Ⅱ from China, Kevlar from DuPont in the United States, Twaron from Aksu in the Netherlands and Technora from Teijin in Japan are compared.