Synthetic fiber made of polyacrylonitrile or acrylonitrile copolymer containing more than 85% (mass percentage) of acrylonitrile. The common second monomer is non-ionic monomer, such as methyl acrylate and methyl methacrylate, and the third monomer is ionic monomer, such as sodium allylsulfonate.

Polyacrylonitrile fiber can be blended with wool to form wool, or woven into blankets, carpets, etc. It can also be blended with cotton, man-made fibers, and other synthetic fibers to form various clothing materials and indoor articles. The expanded body processed by polyacrylonitrile fiber can be pure spun or blended with viscose fiber.