Enhanced Mechanical and Thermal Properties of Polyimide Films Based on Functional Groups-Free Few-Layer Graphene

Graphene has been widely explored to reinforce polyimide (PI) composites for its excellent physical and chemical properties. However, previous works mainly focusing on functionalized reduced graphene oxide and thick graphene as additives have not been able to reveal the influences of intrinsic few-layer graphene without functional groups on performance enhancements, because of the limits in preparation technique of large quantity few-layer graphene nanosheets and poor dispersibility of graphene in a polymer matrix. Herein, we prepare highly uniform few-layer graphene/polyimide (G/PI) nanocomposite films through a solution mix procedure and thermal polymerization. The as-prepared G/PI nanocomposite films show obvious mechanics, thermotics and hydrophobicity enhancements. Compared with neat PI films, the tensile strength increases 30% from 113 to 147 MPa at 0.1% graphene content. The thermal conductivity at 0.05% graphene content reaches 0.2275 W/(m.K), 8.8% higher than that of neat PI. At 0.50% graphene content, water absorption decreases from 1.19 to 0.50% and water surface contact angle increases from 82.95 to 99.95 degrees. The homogeneously dispersed few-layer graphene nanosheets effectively strengthen the interaction between graphene nanosheets and PI matrix, enhance the performances of nanocomposite films with less additive amount of filler, and have negligible effects on stability and electronic properties.