Growth of ultra-dense MoS₂ nanosheets on carbon fibers to improve the mechanical and tribological properties of polyimide composites

To enhance the interface bonding of polyimide (PI)/carbon fiber (CF) composites, CFs were functionalized by introducing a polydopamine (PDA) transition layer, whose active groups provide absorption sites for the growth of molybdenum disulfide (MoS₂) nanosheets and improve the bonding strength with PI. Uniform and dense MoS₂ nanosheets with thicknesses of 30-40 nm on the surface of the PDA@CF were obtained via a subsequent hydrothermal method. As a result, the interface between the CF and the PI matrix becomes more compact with the help of the PDA transition layer and MoS₂ nanosheets. This is beneficial in forming PI/CF-MoS₂ composites with better thermal stability, higher tensile strength, and enhanced tribological properties. The lubricating and reinforcing effects of the hybrid CF-MoS₂ in the PI composite are discussed in detail. The tensile strength of the PI/CF-MoS₂ composite increases by 43%, and the friction coefficient and the wear rate reduce by 57% and 77%, respectively, compared to those of the pure PI. These values are higher than those of the PI/CF composites without MoS₂ nanosheets. These results indicate that the CF-MoS₂ hybrid material can be used as an additive to improve the mechanical and tribological properties of polymers.