The internal lubrication of polyimide (PI) with added 5-wt% nanographite (NG) was investigated in comparison to the tribological performance of a neat PI under point-contact dry sliding conditions with various loads and velocities. NG had a vital role in eliminating the influence of macromolecules decomposed in the PI matrix, according to energy-dispersive X-ray spectrometry, Fourier-transform infrared spectroscopy, and Raman spectroscopy results. When the pressure x velocity reached 56 MPa m/s, a sharp increase was observed in the wear rate of the neat PI. The wear debris consisted of coexisting PI matrix and amorphous carbon. In contrast, NG filler and PI matrix mixtures were the main components in the NG/PI debris. The effect of the NG with a high thermal conductivity on the frictional interface likely prevented the pyrolysis of the PI matrices. Compared to the neat PI, the variations in tribological properties of NG/PI were less affected by the test conditions. For NG/PI, the wear gradually converted from adhesive wear under light load/low velocity to abrasive wear under heavy load/high velocity. The results for the tribological performance and wear mechanism of NG/PI could further contribute to applications under various point-contact dry sliding conditions.
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