Abstract
Three aromatic polyimides based on 3,3′,4,4′-biphenyl-tetracarboxylic dianhydride (BPDA) and three different diamines 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (PFMB), 2,2′-dimethyl-4, 4′-diaminophenyl (DMB) or 3,3′-dimethylbenzidine (OTOL) have been synthesized. These polyimides are soluble in hotp-chlorophenol,m-cresol or other phenolic solvents. Fibers have been spun from isotropic solutions using a dry-jet wet spinning method. The as-spun fibers generally exhibit low tensile properties, and can be drawn at elevated temperatures (>380° C) up to a draw ratio of 10 times. Remarkable increases in tensile strength and modulus are achieved after drawing and annealing. The crystal structures of highly drawn fibers were determinedvia wide angle X-ray diffraction (WAXD). The crystal unit cell lattices have been determined to be monoclinic for BPDA-PFMB and triclinic for both BPDA-DMB and BPDA-OTOL. Thermomechanical analysis (TMA) was used to measure thermal shrinkage stress and strain. A selfelongation has been found in the temperature region around 450°C. This phenomenon can be explained as resulting from the structural development in the fibers as evidencedvia WAXD observations.
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Dedicated to Profeseor Bernhard Wunderlich on the occasion of his 65th birthday
This work was supported by SZDC's Presidential Young Investigator Award from the National Science Foundation (DMR-9175538) and NSA/EPIC/Ohio Industry Center of Molecular and Microstructure Composites at Case Westen Reserve University and The University of Akron.
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Wu, Z., Zhang, A., Shen, D. et al. The crystal structures and thermal shrinkage properties of aromatic polyimide fibers. Journal of Thermal Analysis 46, 719–731 (1996). https://doi.org/10.1007/BF01983598
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DOI: https://doi.org/10.1007/BF01983598