Synthetic fibers made from acrylonitrile copolymers containing more than 85% (by weight) of acrylonitrile. Common monomers include non-ionic types such as methyl acrylate, methyl methacrylate, etc., with the third monomer being ionic, such as sodium acrylate sulfate.

Over a century ago, polyacrylonitrile was produced, but due to the lack of a suitable solvent, it couldn't be spun into fibers. In 1942, Germans H. Rein and Americans G.H. Linstead discovered dimethylformamide solvent almost simultaneously, successfully producing polyacrylonitrile fibers. In 1950, the American DuPont Company was the first to initiate industrial production. Subsequently, various solvents were discovered, leading to multiple production processes. In 1954, the German company Hoechst AG, now part of Bayer, produced fibers using copolymers of methyl methacrylate and acrylonitrile, enhancing fiber properties and practicality, thereby fostering the development of polyacrylonitrile fibers. In 1984, the global production of polyacrylonitrile fibers reached 2.4 million tons.