Study on Cyclohexyl isocyanate-modified Graphene and Mechanical,Thermal and Tribological Properties of its Polyimide Nanocomposite

To elucidate the effect and the mechanism of graphene modification on the morphology and properties of polyimide (PI), cyclohexyl isocyanate modified graphene (CG), was designed and prepared by grafting the isocyanate chain on the graphene sheet surface, followed by the use of the modified graphene for the preparation of polyimide composites by in situ polymerization. The successful grafting of cyclohexyl isocyanate onto the surface of the graphene was confirmed by Fourier transform infrared spectroscopy, X-ray diffraction, and Raman spectroscopy. The unique surface modification significantly improved the compatibility and dispersion of graphene in the PI matrix. CG/polyimide composites were prepared by in situ polymerization. The tensile strength and Young's modulus of the 1.0CG/PI nanocomposite reached 99.35 MPa and 1.84 GPa, showing increases of 20.97 % and 28.67 %, respectively, compared to the values of pure PI. The friction coefficient of the 1.0CG/PI composite reached 0.35, i.e., it was 32.69 % lower than that of pure PI, and the wear rate was reduced by 29.10 %. This improvement of the tribological properties was mainly caused by the cooperative interaction of the mechanical and thermal properties of the composites and the high self-lubricity of modified graphene.