Abstract: After incorporating o-tolidine(OTOL) into 3,3′,4,4′-biphenyltetracarboxylic dianhydride(BPDA) and p-phenylenediamine(PPD) backbone, the mechanical properties of fibers were dramatically improved. The strength and modulus of BPDA/PPD/OTOL polyimide(PI) fiber(diamine molar ratio of n(PPD)∶n(OTOL)=70∶30) attained 1.50 and 80 GPa, respectively, which were two times of the tenacity of BPDA/PPD PI fibers. SEM pictures showed that the cross-sections of the fibers at each stage were circular and voids free, and also no obvious “skin-core” and microfibrillar structure and wide/small angle X-ray scattering(WAXD/SAXS) experiments indicated that the longitudinal stacks and the molecular orientation of PI fiber were improved in the heat-drawn process.

Key words: polyimide fiber, o-tolidine, SEM, wide angle X-ray diffraction, small angle X-ray scattering