Abstract: The special macromolecular polyimide structure, with an average molecular weight exceeding 105 g/mol, was achieved by carefully controlling the polymerization degree in this study. High-tensile and high-strength polyimide fibers were produced by aging the polymerization liquid to a spinnable viscosity at high temperature aging manner, and then treated by cyclization at high temperature and ultrasonic drafting at low temperature after spinning. This study investigates the effects of polymerization degree control, curing temperature of the spinning liquid, viscosity of the spinning liquid, ultrasonic frequency, and drawing temperature influence the mechanical properties of polyimide fibers. Results show that the method described here effectively improves the elongation at break of high-strength, high-modulus polyimide fibers, while also enhancing their tensile strength.

Key words: polyimide; fiber; elongation; ultrasonic; low-temperature drafting