CARBONIZATION AND GRAPHITIZATION OF POLYIMIDE FILM NOVAX

Polyimide films "Novax" consisting of the imide part with the bridging part of a random mixture of two different structures, were carbonized at various temperatures up to 1100-degrees-C and graphitized at 3000-degrees-C. The weight change occurred in two steps, as other polyimide films; large weight decrease in a narrow temperature range between 450-degrees and 600-degrees-C, and a further decrease above 800-degrees-C. The former weight decrease could be explained by the evolution of large amount of CO and CO2 gases, and the latter corresponded to the evolution of N2 gas and rapid increase in electrical conductivity up to 200 S/cm. The thinnest film gave a graphite film with a high degree of graphitization, high value of magnetoresistance, and very low anisotropy ratios.