STRUCTURAL-CHANGES FROM POLYIMIDE FILMS TO GRAPHITE .4. NOVAX AND PPT

Various polyimide films (Kapton, Upilex, Novax, and PPT) were carbonized and graphitized up to 3000 degrees C. They were studied by optical and electron microscopies. All films retaining oxygen as a cross linker over 1000 degrees C, i.e., Kapton, Upilex, and Novax, graphitize as anthracites (high rank coals) do. They get a long range statistical orientation parallel to the film plane with a nanotexture of flattened pores. Graphitization is both sudden and perfect above 2100 degrees C when the pore walls break. Since oxygen is released at 1000 degrees C, the film PPT behaves as a compact nonporous graphitizing carbon (orientation parallel to the film plane). Thermal graphitization is progressive and begins at a higher temperature.