Effects of nanoscale expanded graphite on the wear and frictional behaviors of polyimide-based composites

The effects of adding nanoscale lamellar-structure expanded graphite (nano-EG) on the friction and wear properties of hot-molded polyimide (PI)-based composites were investigated. Friction and wear tests were carried out using a Type 1045 steel ring rotating against a composite disk. The coefficients of friction, wear rate, worn surface morphology were investigated. Experimental results indicated that the tribological properties of PI/nano-EG composites highly depend on the content of nano-EG under dry sliding conditions. Compared with that of PI, wear resistance of PI/nano-EG composites was increased by a factor of 200. Best tribological properties occurred when the nano-EG content is 15 wt%. The transfer film generated on the mating surface of the self-lubricating PI/nano-EG composite is smooth and continuous, which is likely to be responsible for its low wear rate. Such composites can offer considerable potential for engineering applications such as bearings and slideways where they can reduce both the friction coefficient and the wear rate.