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.%在3,3′,4,4′-联苯四酸二酐(BPDA)和对苯二胺(PPD)体系中引入3,3′-二甲基联苯胺(OTOL),显著改善了纤维的力学性能.当n( PPD)∶n(OTOL) =70∶30时,纤维的拉伸强度可达到改性前的2倍,其拉伸强度和拉伸模量分别为1.50和80 GPa.SEM照片显示了纤维的断面为圆形且没有孔穴,也没有明显的“皮芯”结构和原纤结构.WAXD和SAXS分析表明,纤维的轴向堆积和分子链取向在热牵伸过程中得到改善.
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