Friction and Wear Properties of Polyimide-Based Composites with a Multiscale Carbon Fiber-Carbon Nanotube Hybrid

Abstract

A multiscale carbon fiber-carbon nanotube (CF-CNT) hybrid was fabricated via chemical method, and then the corresponding polyimide (PI) composites were prepared using hot pressing technique. The microstructure and chemical composition of the CF-CNT hybrid were characterized, and its enhancement mechanisms on the tribological properties of PI were investigated systematically. Results showed that the CF-CNT hybrid had many functional groups and increased roughness, which was good for ameliorating the interfacial combination between the CF and PI matrix, further indicating that the PI/CF-CNT composite possesses excellent friction and wear properties. The friction coefficient and wear rate of the PI/CF-CNT composite were 0.213 and 1.79 × 10−6 mm3/Nm, i.e., a decrease of 22 and 72%, respectively, compared to pure PI. In particular, the friction coefficient and wear rate of the PI/CF-CNT composite decreased with increasing applied load or sliding rate, suggesting that PI/CF-CNT was an excellent self-lubricating material. This was closely related to the enhanced interfacial adhesion between CF and PI. More importantly, CNT onto a CF-CNT hybrid surface could stretch into the PI matrix, which had a reinforcing effect on the PI matrix and also, just like many fibrous roots around the main root of a tree, helped the CF not break under repeated stresses during the friction and wear process, even under high load or sliding rate.