Hollow if-mos₂/r-go nanocomposite filled polyimide coating with improved mechanical, thermal and tribological properties

Polyimide (PI) is one of the most excellent polymers for coating. However, the high friction coefficient and the high wear rate of pure PI limit its further applications. In this work, the hollow inorganic fullerene-like MoS₂/reduced graphene oxide (HIF-MoS₂/r-GO) nanocomposite filled PI coating is prepared by in situ polymerization. Reinforcement in mechanical strength and thermal stability is realized on the PI composite coating with incorporation of HIF-MoS₂/r-GO, which performs better than carbon nanofiber (CNF). Reduced elastic modulus and hardness of HIF-MoS₂/r-GO/PI coating is increased by 8.3% and 4.8%, respectively. The addition of HIF-MoS₂/r-GO also results in 24% higher residual mass at 800^◦C than CNF. Tribological study indicates that, HIF-MoS₂/r-GO/PI achieves a wear rate reduction of 79% compared with pure PI under dry sliding condition, which is much more effective than other nanofillers including CNF, r-GO nanosheets and MoS₂ nanoparticles. Under ionic liquid-lubricated condition, the presence of HIF-MoS₂/r-GO in PI results in a 30% reduction in wear rate and 10% reduction in friction coefficient as compared to pure PI. It is thought that the HIF-MoS₂/r-GO in PI can be slowly released to the frictional interface and form a protective film during sliding, in this way the aggregation problem is successfully solved.