Frictional properties of carbon nanofiber reinforced polymer matrix composites

Carbon nanotubes (CNTs) are expected to be a new functional material. We fabricated polystyrene (PS) matrix composites filled with multiwalled carbon nanotubes (MWCNTs) and vapor grown carbon fibers (VGCFs). The concentration of the fillers in the composites was varied from 0 to 50 wt%. Specimens were fabricated by injection molding, and the friction coefficient and wear resistance of the surface of the molded specimens were measured using a ball-on-disk friction tester. In the case of VGCF/PS composites, the friction coefficient decreased with increasing the filler concentration, although the surface roughness increased with the filler concentration. Finally, the friction coefficient decreased from mu=0.45 to mu=0.2 when the VGCF concentration was 50 wt%. In the case of MWCNT/PS composites, the friction coefficient was almost the same as that of bulk PS when the MWCNT concentration was 30 wt%. The change in the friction coefficient of CNT/PS composites was discussed in terms of the surface roughness, CNT contact area and Young's modulus. The specific wear rate of CNT/PS composites was also measured. The wear rate of MWCNT was 2.0 x 10(-7) mm(3)/N, which is eightfold smaller than that of VGCF/PS composites.