Polyacrylonitrile (PAN) is a synthetic, semicrystalline organic polymer resin, with the linear formula (C3H3N)n. Though it is thermoplastic, it does not melt under normal conditions. It degrades before melting. It melts above 300 degrees Celsius only if the heating rates are 50 degrees per minute or above. [1] Almost all polyacrylonitrile resins are copolymers made from mixtures of monomers with acrylonitrile as the main component. It is a versatile polymer used to produce large variety of products including ultra filtration membranes, hollow fibers for reverse osmosis, fibers for textiles, oxidized flame retardant fibers like PANOX and carbon fiber. PAN fibers are the chemical precursor of high-quality carbon fiber. PAN is first thermally oxidized in air at 230 degrees to form PANOX and then carbonized above 1000 degrees in inert atmosphere to make carbon fibers found in plenty of both high-tech and common daily applications such as civil and military aircraft primary and secondary structures, missiles, solid propellant rocket motors, pressure vessels, fishing rods, tennis rackets, badminton rackets & high-tech bicycles. It is a component repeat unit in several important copolymers, such as styrene-acrylonitrile (SAN) and acrylonitrile butadiene styrene (ABS) plastic.
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All commercial methods of production of PAN is based on free radical polymerization of Acrylonitrile (AN). Most of the cases, small amount of other vinyl comonomers are also used (1-10%) along with AN depending on the final application.[2]. Anionic polymerization also can be used for synthesizing PAN. For textile applications, molecular weight in the range of 40,000 to 70,000 is used. For producing carbon fiber higher molecular weight is desired.
Homopolymers of polyacrylonitrile have been used as fibers in hot gas filtration systems, outdoor awnings, sails for yachts, and fiber-reinforced concrete. Copolymers containing polyacrylonitrile are often used as fibers to make knitted clothing like socks and sweaters, as well as outdoor products like tents and similar items. If the label of a piece of clothing says "acrylic", then it is made out of some copolymer of polyacrylonitrile. It was made into spun fiber at DuPont in 1941 and marketed under the name of Orlon. Acrylonitrile is commonly employed as a comonomer with styrene (e.g. SAN, ABS, and ASA (acrylonitrile styrene acrylate) plastics).