a linear polymer [-CH₂-CH(CN)—]_n of acrylonitrile; an amorphous white substance. Molecular weight, 30,000–100,000; and density, 1.14–1.15 g/cm³ (20°C). Does not soften up to almost 230°C (degradation takes place above this temperature). Polyacrylonitrile is comparable in strength to polyamides (for example, nylon). Its relative elongation is 10–35 percent, its water absorption is 0.9–1.0 percent at 20°C and 65 percent relative humidity.

Polyacrylonitrile is chemically resistant to the action of ordinary solvents and fats and is not altered by atmospheric conditions and sunlight. It dissolves, for example, in dimethylforma-mide, dimethylacetamide, and ethylene carbonate, in concentrated aqueous solutions of the salts LiBr, NaCNS, Ca(CNS)2, and ZnCl₂ + CaCl₂; and in concentrated nitric and sulfuric acids.

In industry, polyacrylonitrile is produced by radical polymerization of the monomer in an aqueous medium or in aqueous solutions of salts. Polyacrylonitrile is used mainly for producing high-quality textile polyacrylonitrile fibers.