Polyacrylonitrile

Polyacrylonitrile (PAN) is a synthetic polymer produced from the monomer acrylonitrile. Its repeating unit is −CH2−CH(CN)−. PAN is a thermoplastic polymer with a high density of nitrile groups, which impart polarity, chemical resistance, and strong interactions with dyes and fillers.

PAN is prepared by free-radical polymerization of acrylonitrile, often with small amounts of comonomers to tailor processing and properties. Commercial PAN typically contains about 85–95% acrylonitrile, with the remaining portion comprising co-monomers that improve spinnability, dyeability, and thermal behavior. The polymer is soluble in several polar aprotic solvents, enabling solution-based fiber or film processing from solvents such as dimethylformamide, dimethylacetamide, or N-methylpyrrolidone.

The principal use of PAN is as a precursor for carbon fibers. PAN fibers are stabilized by oxidative treatment in air at roughly 200–300°C to form a cyclized structure, then carbonized under inert atmosphere at 1000–1500°C to produce carbon fibers with high tensile strength and modulus. Beyond carbon fiber production, PAN is used for specialty fibers and films that benefit from its chemical resistance and thermal stability, and PAN fibers can be dyed due to their nitrile content.

Safety and handling considerations stem from the acrylonitrile monomer, which is toxic and requires appropriate controls during polymerization and processing. As a versatile precursor, PAN continues to be developed for enhanced processability, dye affinity, and carbon-fiber performance.