The process for the formation of high-modulus structure was re-examined through the cast films fabrication study for poly (bis 2,2-disubstituted biphenylene pyromellite imides (PBPPI-X X: substituents). As the result, it has been clarified that the imide-cyclization behaiviors during intermediate curing zone below 250 °C play influential parts and the introduction of volumetrically moderate substituents like methyl group and so on are helpful for the improvement of tensile properties. The reason can be consistently explained from TMA diagrams in this intermediate curing zone rather than from WARD profiles.
Yokohama
JAPANThe concept of molecular composites was re-evaluated through the mechanical and morphological studies on the cast film forming from the rod/coil -typed block co-polyimide.The
research centerThe nuclear-substituent effects on rigid-rod polyimide was discussed, through the benzobisthiazole containing poly p-phenylenepyromelliteimide (PIBT)-related system.The noticeable effect was observed in terms of the retrogressive gel forming tendency through the chemical cyclization of polyamide acid solution.The solubility-up of the partially imidized precursors is derived from the enhancement of the backbonechains motional freedom and assumed to be effective for the backbone chains're-alignments to build up the high-modulus ordered structures. Such assumptionis certificatedby the tensile improvement in PIBT-2-CH3 (2-CH3 -substituted ) cast films as shown below ,or the WAXD profile which is analogous to that of PIBT(nonsubstituted) uniaxially drawn films.Young's modulus I Tensile strength for cast films PIBT (non substituted) 16GPa 10.1 GPa PIBT-2-CH3 (2-methyl substituted ) 21GPa 10.4GPaKeywords; nud ear susti tud on? hetero-cyd a containing rigid-rod polyln ide, mechanical properties
A novel polyimide-based heterocyclic polymer, polyimide benzobisthiazole (PIBT), was prepared from diaminophenylene benzobisthiazole (DAPBT) and pyromellitic acid dianhydride (PMDA). Fibers with tensile modulus of 220 GPa were obtained from PIBT; this modulus value is consistent with the 430 GPa modulus determined by wide-angle x-ray diffraction (WAXD) analysis. Unoriented isotropic films exhibited significantly lower modulus values in the range of 10 GPa. Block copolymers of PIBT with thermoplastic segments were synthesized in an effort to prepare molecular composites. These materials showed a dramatic decrease in melt viscosity and had modulus values lower than observed in isotropic PIBT films.
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