Synthetic fibers made from acrylonitrile copolymers containing over 85% (by weight) acrylonitrile, with commonly used monomers being non-ionic, such as methyl丙烯ate, methyl methacrylate, etc., and the third monomer being ionic, such as sodium acrylate sulfonate.

Polyacrylonitrile fiber has a high purity requirement for the monomer acrylonitrile, with the total content of various impurities to be less than 0.005%. The monomers used in polymerization are mainly methyl丙烯酸甲酯, with methyl methacrylate also being an option. The purpose is to enhance the spinnability and the hand, softness, and elasticity of the fiber; the third monomer primarily improves the dyeability of the fiber, typically using itaconic acid containing weakly acidic dye groups, sodium acrylate with strongly acidic dye groups, sodium methacrylate, sodium p-methacrylamide benzenesulfonate, and methyl vinyl pyridine containing basic dye groups.