CARBONIZATION AND GRAPHITIZATION OF KAPTON-TYPE POLYIMIDE FILMS PREPARED FROM POLYAMIDE ALKYL ESTER

Polyamide acid was prepared from pyromellitic dianhydride (PMDA) and o xydianiline (ODA), and was then reacted with NaH and various kinds of alkyl halides for transformation into alkyl ester. The cast films were imidized as fixed on glass substrate to give Kapton-type polyimide fi lms, and were then carbonized by heating to 900 degrees C. It was show n that the electrical conductivity of the carbonized films decreased w ith the increase of the size of the leaving group at the imidization. The carbonized films were further heated to 2800 degrees C for graphit ization. Their degrees of graphitization and orientation of the graphi te crystallites as a function of weight loss at imidization were studi ed by X-ray diffraction measurements at room temperature and magnetore sistance measurements at liquid nitrogen temperature. Both measurement s clearly indicate that the graphitized films prepared from polyamide acid alkyl ester starting from PMDA and ODA have high degrees of graph itization. It was also made clear that, in the case of polyimide havin g flexible ether linkage, the orientation of the graphitized films did not depend on the size of the leaving group at imidization. (C) 1997 Elsevier Science Ltd.