Three Kinds of aromatic polyimides, pyromellitic dianhydride (PMDA)/p-phenylenediamine (PPD)/3, 3', 4, 4'-biphenylene tetraamine (TAB), 3, 3', 4, 4'-biphenyltetracarboxylic dianhydride (BPDA)/PPD and PMDA/4, 4'-diaminodiphenyl ether (DPE), were heat-treated at about 1000°C and further heat-treated at 2300°C under inert gas atmosphere and carbon films were prepared. It was confirmed by X-ray analysis and scanning electron microscopic measurements that the amount of graphite carbon of PMDA/PPD/TAB films was higher than that of BPDA/PPD and PMDA/DPE. This is due to the fact that the molecular chain of PMDA/PPD/TAB forms a coplanar structure. Preheat-treated films were unidirectionaly drawn and then carbonized. PMDA/PPD/TAB films, which showed the highest orientation of polymer chains, exhibited the highest values of dynamic modulus and electric conductivity. During carbonization, the oriented carbon layers grew along the drawn direction. The results indicates that the ordered structure of precursor polyimide films affects the properties of carbonized polyimide films.
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