Abrasive wear resistance of injection molded polycarbonate (PC) and polycarbonate+zinc oxide nanocomposites containing 0.5 wt% ZnO nanoparticles was determined as a function of the sliding direction with respect to injection flow. First we have performed single scratch testing under progressively increasing the load applied. Then sliding wear testing consisting of 15 successive scratches along the same groove was performed. Neat PC shows anisotropic behavior, with instantaneous penetration depth more than 50% higher in the direction parallel to the melt injection flow than in the transverse direction. Viscoelastic recovery after scratching of neat PC is also higher in the longitudinal than in the transverse direction, hence final residual depth values are similar in both directions. The addition of ZnO nanoparticles reduces the instantaneous penetration depth in the longitudinal direction but lowers viscoelastic recovery so that the residual depth is large. In the transverse direction, the scratch resistance is similar for neat PC and the nanocomposite. Dynamic mechanical analysis, SEM/FIB results and wear mechanisms from SEM observations of wear scars are discussed. Below the glass transition region the nanocomposite has distinctly higher storage modulus E' than PC—a clear reinforcement effect. However, the addition of ZnO nanoparticles to the polymer increases the material brittleness at room temperature by a factor of 2.72.

The present overview will focus on the tribological applications of what we have called ionanocarbon lubricants, that is, the combination of carbon nanophases (graphene, carbon nanotubes, nanodiamonds, carbon nanodots) and room-temperature ionic liquids in new dispersions, blends, or modified nanostructures and their use in tribology, lubrication, and surface engineering as friction-reducing, antiwear, and surface-protecting agents in thin films and composite materials. Further research lines and factors that limit the practical applications of the outstanding research results are also highlighted. The very recent results in these lines of research make this a necessary brief review.

Polylactic acid (PLA)-based nanocomposites were prepared by twin-screw extrusion. Graphene oxide (GO) and an ionic liquid (IL) were used as additives separately and simultaneously. The characterization of the samples was carried out by means of Fourier transform infrared (FT-IR) and Raman spectroscopies, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The viscoelastic behavior was determined using dynamic mechanical analysis (DMA) and rheological measurements. IL acted as internal lubricant increasing the mobility of PLA chains in the solid and rubbery states; however, the effect was less dominant when the composites were melted. When GO and IL were included, the viscosity of the nanocomposites at high temperatures presented a quasi-Newtonian behavior and, therefore, the processability of PLA was highly improved.