Structural evolution and thermal conductivity of flexible graphite films prepared by carboxylic graphene/polyimide

Abstract Graphene (GN) is transformed into carboxylic graphene (GO-COOH) with carboxylic groups by acidizing. Carboxylic graphene/polyimide (GO-COOH/PI) composite films are prepared by in-situ polymerization. The composite films show strong intermolecular force compared to the PI films which leads to excellent tensile strength and thermal conductivity. The composite films can be transformed into carbon films and graphite films by carbonization and graphitization. The GO-COOH can induce the graphitization process and compensate the defects. The thermal conductivity of graphite films prepared by composite films graphitized at the same temperature is higher compared to that of PI films. The addition of GO-COOH has a great effect on reducing carbonization and graphitization temperature and improving property of films. The graphite films treated with 2500 °C possess smoother surface and the color of graphite films turn into dark grey. The films can keep the integral state and bend to a certain extent which exhibits that the flexibility of the graphite films is improved. The thermal conductivity of graphite films prepared by composite films treated with 2500 °C is 760.386 W/mK and increases by 128% compared to that prepared by the PI films, which is suitable for the application of heat conduction.