EFFECT OF CONSTRAINT DURING IMIDIZATION OF POLYAMIC ACID FILMS ON GRAPHITIZABILITY OF RESULTANT CARBON-FILMS

Three kinds of polyimide film specimens were prepared by imidizing polyamic acid under different constraint conditions (viz. as fixed on a glass substrate), in free space, and with 20% stretching in length, respectively. X-ray diffraction and magnetoresistance parameters were measured after their graphitization at 3000-degrees-C. The films prepared under constraint, on a glass and with stretching, were found to be highly graphitizable, showing small interlayer spacing, large crystallite size along the c-axis, high magnetoresistance, and high degree of preferred orientation of graphite layers, as compared with that prepared in free space. These results imply that the orientation of molecules in the polyimide film is very important in order to get graphite films with high crystallinity and high degree of orientation.