▎ 摘　　要

NOVELTY - Polyimide/graphene nanobelt composite film is obtained by dissolving water-soluble polyimide in deionized water, obtaining water-soluble polyimide solution, adding graphene nanobelt solution, obtaining mixed solution (C), stirring, obtaining graphene nanobelts/polyamic acid solution, spin-coating, casting or spreading on clean glass plate, placing glass plate in high temperature furnace at 60 degrees C at the rate of 5-10 degrees C/minute, heating at 100 degrees C for 2 hours, and increasing the temperature to 100-350 degrees C at the heating rate of 5-10 degrees C/minute. USE - Preparation of polyimide/graphene nanobelt composite film (claimed). ADVANTAGE - The method efficiently provides polyimide/graphene nanobelt composite film having excellent insulation property and mechanical property, and low dielectric constant. DETAILED DESCRIPTION - 4,4'-Diaminodiphenylether is added to organic solvent, and stirred at the speed of 100-300 rpm for 60 minutes, ultrasonically processed in the ultrasonic power of 300 W for 6-12 hours, to obtain diamine solution. Dianhydride is added to obtained diamine solution, placed in ice-water bath at the stirring rate of 100 rpm to obtain viscous polyamic acid solution. The mass ratio of 4,4'-diaminodiphenyl ether with respect to organic solvent is 3 g:40-60 mL. The organic solvent is N-methylpyrrolidone or N-dimethylformamide. The dianhydride is biphenyl-type dianhydride or homo-benzene-type dianhydride. Biphenyl-type dianhydride is 3,3',4,4'-biphenyltetracarboxylic dianhydride. Pyromellitic dianhydride is pyromellitic dianhydride. The molar ratio of dianhydride with respect to 4,4'-diaminodiphenyl ether is 1:1. A weakly basic agent is added to viscous polyamic acid solution, reacted under nitrogen atmosphere, stirred at the speed of 100-300 rpm for 20-30 hours, cleaned using cleaning agent, centrifuged and supernatant is removed, to obtain water-soluble polyimide. The volume ratio of polyamic acid solution with respect to weakly alkaline agent described is 10:1. Graphene nano-band solution is obtained by adding carbon nanotubes and oxidants to concentrated acid, obtaining mixture (A), stirring in ice water bath at the stirring speed of 100-300 rpm for 1-2 hours, heating at 60 degrees C, heat-preserving at 60 degrees C for 1-3 hours, centrifuging at the speed of 6000-8000 rpm for 10-15 minutes, removing supernatant, obtaining solid (B), washing obtained solid using 5-10% hydrochloric acid, washing using distilled water, obtaining graphene nanobelts and dissolving graphene nanobelts in deionized water. The volume ratio of carbon nanotubes with respect to concentrated acid is 1 g:80-100 mL. The mass ratio of carbon nanotubes with respect to oxidant is 1:5-8. The concentration of the graphene nanobelts in the graphene nanobelts solution is 1-5%. Polyimide/graphene nanobelt composite film is obtained by dissolving water-soluble polyimide in deionized water in the volume ratio of 5 g:10-20 ml, obtaining water-soluble polyimide solution, adding graphene nanobelt solution, obtaining mixed solution (C), stirring for 24-36 hours at a stirring speed of 100-300 rpm, obtaining graphene nanobelts/polyamic acid solution, spin-coating, casting or spreading on clean glass plate, placing glass plate in high temperature furnace at 60 degrees C at the rate of 5-10 degrees C/minute, heating at 100 degrees C for 2 hours, and increasing the temperature to 100-350 degrees C at the heating rate of 5-10 degrees C/minute. The content of graphene nanobelt in the mixed solution (C) is 0.1-3 %mass.