Abstract: Lightweight, high-strength, organic high-performance fibers with a wide temperature range are often used in high-temperature filtration, national defense, military, special protection, aerospace and other fields. In order to explore the heat resistance and structural changes of several organic high-performance fibers, i.e., the polyimide fiber (PI) and polyarylate fiber (PAR)^®, polyarylate fiber (PAR) Yokolar^® and aramid Ⅲ fiber, Vectran scanning electron microscope, thermogravimetric analyzer, and Fourier infrared spectrometer were used to study. The surface morphology, tensile properties, and chemical structure changes of four organic high-performance fibers after being treated at a high temperature of 200 ℃ to 350 ℃ for a certain period of time. The results show that: PI, Vectran^®, Yokolar^® and Aramid Ⅲ fiber have a breaking stress of 3.3 GPa, 4.0 GPa, 3.9 GPa and 5.0 GPa. After a long time treatment at 200 ℃~350 ℃, the PI fiber surface has no obvious defects, the other three types of fiber grooves, particles and other defect structures have increased. The characteristic peaks of the infrared spectrum of PI fiber have not changed significantly, and the corresponding functional groups have not been completely destroyed by high temperature. The other three kinds of fibers' infrared spectra characteristic peaks have different degrees of weakening or disappearance, some chemical bonds are broken; heat resistance PI>Aramid Ⅲ>Vectran^®>Yokolar^®, the temperature corresponding to 5% mass loss is 529 ℃, 506 ℃, 472 ℃ and 445 ℃. Molecular chain breakage and the increase of fracture and surface defects are the key influencing factors for the decline of fiber mechanical properties.

Key words: organic high-performance fiber, heat resistance, polyarylate, polyimide, aramid Ⅲ, composites