These are a class of heat-resistant and fairly strong synthetic fibers of orange to yellow color.
They are prepared by a two-step process from aromatic diamines and dianhydrides. Polyimides perform in demanding applications where very high temperature, corrosion, wear, and creep resistance is required. Polyimides fibers are produced by a dry-spinning process from a polyamic acid solution. The precursor fibers are then transferred into polyimide fibers by a subsequent heat treatment process. Unlike polyester and acrylic fibers, polyimides have a much higher glass transition temperature (about 400°C) and a much higher melting point. Due to their aromatic structure, polyimide fibers have very low flammability and excellent chemical resistance Continue reading here