Comparative Study on Dry and Wet Wear Characteristics of Ultra-High Molecular Weight Polyethylene Composites Reinforced with Direct Precipitated Nano Zinc Oxide

The tribological behavior of Ultra-High Molecular Weight Polyethylene (UHMWPE) composites, reinforced with nano-sized Zinc Oxide (ZnO) particles, was systematically investigated under both dry and wet conditions.Composites were fabricated via hot compression molding, ensuring homogeneous nanoparticle distribution and effective bonding.Wear rates in dry conditions were assessed using a pin-on-disc apparatus, with a composite pin against a 63 HR EN31 steel disc, while wet tribology tests employed distilled water as a lubricant.Post-experimental Scanning Electron Microscopy (SEM) analyses revealed distinct wear mechanisms between the two environments.Under dry conditions, an increase in wear rates and frictional forces was observed for the composites, whereas the introduction of water as a lubricant significantly reduced wear rates in wet conditions.The presence of nano ZnO was found to enhance the mechanical properties and wear resistance of UHMWPE, particularly in the presence of lubrication.When subjected to a 100rpm and 10N load, the UHMWPE composite with a 10wt% ZnO filler exhibited a marked reduction in weight loss (1.1mg) in comparison to the unfilled UHMWPE (5.1mg).This improvement was sustained at elevated speeds and loads, indicating that higher filler concentrations correlate with improved wear resistance.Wet wear testing further demonstrated the advantageous role of nano ZnO, with UHMWPE composites incurring less weight loss than their unfilled counterparts.The hydrophobic nature of nano ZnO was instrumental in reducing wear under lubricated conditions.These findings underscore the potential for nano ZnO reinforced UHMWPE composites in applications demanding high wear resistance, such as in biomedical implants and automotive components.Moreover, the hydrophobic properties of nano ZnO suggest additional benefits in wet environments.Future work should focus on optimizing nano ZnO loadings for maximum wear resistance and exploring the integration of other reinforcing agents to create composites with multifaceted functional attributes.