The effect of hybrid reinforcement of fMWCNT and nHA to UHMWPE mechanical and tribological properties

Ultra-high molecular weight polyethylene (UHMWPE) is widely utilized for artificial joints to its superior wear resistance and biocompatibility. Nevertheless, restricted mechanical strength and surface hardness still pose a challenge, and formation of wear debris can lessen implant life. In this research, UHMWPE was reinforced with functionalized multi-walled carbon nanotubes (fMWCNTs) in combination with nano-hydroxyapatite (nHA) as hybrid nanofiller (HNF) to enhance both mechanical and tribological features. The fMWCNTs were prepared by oxidative-ammonolysis treatment, confirmed by FT-IR analysis showing hydroxyl, carbonyl, and amine functional groups that enhanced compatibility and bonding strength with the polymer matrix. Nanocomposites with HNF concentrations ranging from 0.5% to 5.0 wt% were fabricated and characterized for tensile, flexural, hardness, and wear performance. The resulting data revealed that the addition of HNFs (1:1 in wt%) improved all mechanical characteristics at low and intermediate loadings, with the optimum enhancement at 3.0 wt%. This particular specimen displayed increases of (11.6, 12.4, and 9.6)% in each tensile strength, flexural strength, and hardness, respectively, relative to the neat polymer. In addition, a decrease of 63.0% of specific wear rate implies exceptional wear resistance owing to homogeneous filler distribution and stable tribofilm development. However, a high content of 5.0 wt% demonstrated minimized mechanical efficiency caused by agglomeration, as reflected in FE-SEM images. These findings indicate that fMWCNTs- nHA blending yields a synergistic enhancement of strength, hardness and wear resistance of the matrix, making the present hybrid system a potential prospect in orthopedic implant uses.