Aramid

Aramid fibers are a class of heat-resistant and strong synthetic fibers. They are used in aerospace and military applications, for ballistic-rated body armor fabric and ballistic composites, in bicycle tires, marine cordage, marine hull reinforcement, and as an asbestos substitute. The name is a portmanteau of 'aromatic polyamide'. The chain molecules in the fibers are highly oriented along the fiber axis. As a result, a higher proportion of the chemical bond contributes more to fiber strength than in many other synthetic fibers. Aramides have a very high melting point (>500 °C)A manufactured fiber in which the fiber-forming substance is a long-chain synthetic polyamide in which at least 85% of the amide linkages, (−CO−NH−) are attached directly to two aromatic rings. Aramid fibers are a class of heat-resistant and strong synthetic fibers. They are used in aerospace and military applications, for ballistic-rated body armor fabric and ballistic composites, in bicycle tires, marine cordage, marine hull reinforcement, and as an asbestos substitute. The name is a portmanteau of 'aromatic polyamide'. The chain molecules in the fibers are highly oriented along the fiber axis. As a result, a higher proportion of the chemical bond contributes more to fiber strength than in many other synthetic fibers. Aramides have a very high melting point (>500 °C) Aromatic polyamides were first introduced in commercial applications in the early 1960s, with a meta-aramid fiber produced by DuPont as HT-1 and then under the trade name Nomex. This fiber, which handles similarly to normal textile apparel fibers, is characterized by its excellent resistance to heat, as it neither melts nor ignites in normal levels of oxygen. It is used extensively in the production of protective apparel, air filtration, thermal and electrical insulation, as well as a substitute for asbestos. Meta-aramid is also produced in the Netherlands and Japan by Teijin Aramid under the trade name Teijinconex, in Korea by Toray under the trade name Arawin, in China by Yantai Tayho under the trade name New Star, by SRO Group (China) under the trade name X-Fiper, and a variant of meta-aramid in France by Kermel under the trade name Kermel. Based on earlier research by Monsanto Company and Bayer, para-aramid fiber with much higher tenacity and elastic modulus was also developed in the 1960s and 1970s by DuPont and AkzoNobel, both profiting from their knowledge of rayon, polyester and nylon processing. In 1973 DuPont was the first company to introduce a para-aramid fiber, which it called Kevlar, to the market; this remains one of the best-known para-aramids and/or aramids. In 1978, Akzo introduced a similar fiber with roughly the same chemical structure, which it called Twaron. Due to earlier patents on the production process, Akzo and DuPont engaged in a patent dispute in the 1980s. Twaron subsequently came under the ownership of the Teijin Company. In 2011, Yantai Tayho introduced similar fiber which is called Taparan in China. (See Production.) Para-aramids are used in many high-tech applications, such as aerospace and military applications, for 'bullet-proof' body armor fabric. Both meta-aramid and para-aramid fiber can be used to make aramid paper. Aramid paper can be used as electrical insulation materials and construction materials to make honeycomb core. Dupont made aramid paper in 1960s, which is called Nomex paper. Yantai Metastar Special Paper introduced aramid paper in 2007, which is called metastar paper. Both Dupont and Yantai Metastar can make meta-aramid and para-aramid paper. The Federal Trade Commission definition for aramid fiber is: During the 1990s, an in vitro test of aramid fibers showed they exhibited 'many of the same effects on epithelial cells as did asbestos, including increased radiolabeled nucleotide incorporation into DNA and induction of ODC (ornithine decarboxylase) enzyme activity', raising the possibility of carcinogenic implications. However, in 2009, it was shown that inhaled aramid fibrils are shortened and quickly cleared from the body and pose little risk. A declaration of interest correction was later provided by the author of the study stating that 'This review was commissioned and funded by DuPont and Teijin Aramid, but the author alone was responsible for the content and writing of the paper.' World capacity of para-aramid production was estimated at about 41,000 tonnes per year in 2002 and increases each year by 5–10%. In 2007 this means a total production capacity of around 55,000 tonnes per year.