Tribological properties of composites of polyamide-6 and nanotubes of MoS2, and nanowires of MoO(3−x) and Mo6S2I8

Composites of Mo6S2I8-nanowires, MoO(3−x)-nanowires and MoS2-nanotubes with polyamide 6 (PA6) have been prepared in different concentrations up to 4% via melt-mixing using a laboratory twin screw extruder in order to investigate their tribological, mechanical and thermal properties. Chemical and structural composition of these nanowires and nanotubes with similar morphologies seem to play an important role in properties of fabricated polymer composites. Tribological tests were performed on the macroscale using a pin-on-disc (POD) tribometer and the thermal properties of the polymer nanocomposites were measured by differential scanning calorimetry to determine their glass transition temperatures and the levels of crystallinity. The behaviour of the nanowires (Mo6S2I8 and MoO(3−x)) is different from the nanotubes (MoS2) with respect to the induced effects on the friction coefficient and wear rate in function of concentration. The composites with the nanowires show a significant increase of the E-module of up to 38% at a nanowire concentration of 4 wt% in the glassy state of PA6, estimated from hardness measurements. The reduced friction coefficient and wear rates are related to the increased bulk shear strength of the nanowire polymer composites. In contrasts, nanotubes of MoS2 did not show this strong reinforcement. The reduced friction coefficients and wear rates of the polymer composites with MoS2-nanotubes are predominantly related to the lubricating effect of the MoS2-nanotubes at the contact points.