Study of the tribological synergistic effects in nano CuO-filled and fiber-reinforced polyphenylene sulfide composites

Nanosize CuO-filled and fiber-reinforced polyphenylene sulfide (PPS) composites were prepared by compression molding. The tribological behaviors of these materials and the synergism as a result of the incorporation of both the nanoparticles and the fibers were investigated. The reinforcement materials were short carbon fibers (CF) and aramid (Kevlar) fibers. The proportions of the filler material varied from 1 to 4 vol.% and of the reinforcement material from 5 to 15 vol.%. For the measurement of wear volume and the coefficient of friction, a pin-on-disk sliding configuration was used. The counterface was made of tool steel hardened to 55-60 HRC and finished to 0.09-0.11 μm Ra. Wear tests were run at a sliding speed of 1 m/s and over a duration of 6 h, which provided the wear data for steady state sliding. In case of the filler only, the lowest steady state wear rate was observed for PPS + 2%CuO composite and of the fiber reinforcement only for PPS + 10%Kevlar composite. The particulate filler did not affect much the coefficient of friction while the latter was reduced to half of that in the case of CF reinforcement. The lowest steady state wear rates that were obtained with hybrid composites made with nanosize CuO particles and fiber reinforcement both could not be obtained with the composites made with either the filler or the fiber reinforcement only. With Kevlar fiber reinforcement alone, the coefficient of friction did not change much. With reinforcement of the CuO-filled polymer with Kevlar fibers, the coefficient of friction increased, but with reinforcement with carbon fibers it either decreased or remained unaffected. The transfer films were studied by optical microscopy and the topographical changes of transfer films by atomic force microscopy (AFM). Worn surfaces and transfer films on the counterface were also studied by scanning electron microscopy.