Tribological Properties and Biocompatibility Studies of PEEK and Its Composites

Polyetheretherketone (PEEK) is a high-performance polymer widely explored for biomedical applications due to its excellent mechanical strength, chemical stability, and biocompatibility. However, its bioinert nature limits osteointegration, requiring reinforcement with bioactive ceramics. In this study, PEEK was reinforced with nano-hydroxyapatite (nHA) at 8, 16, and 24 wt.% and fabricated into composites using extrusion and 3D printing. The tribological, thermal, chemical, and biological properties of the composites were systematically evaluated. Wear tests revealed that pure PEEK exhibited the lowest wear volume (0.05 mm³ at 2.5 km), whereas increasing nHA content led to higher wear due to particle pull-out and brittleness. Hardness improved significantly with reinforcement, peaking at 45 VHN for 16 wt.% nHA, indicating an optimal balance between strength and bioactivity. DSC analysis confirmed minimal changes in thermal transitions, with Tg maintained at 152–153°C and Tm within 342–345°C, demonstrating excellent thermal stability. FTIR spectra verified the successful incorporation of nHA without altering PEEK’s backbone chemistry, while corrosion tests showed an increase in current density at 8 wt.% (0.15 μA/cm²) followed by stabilization at higher filler levels. SBF immersion studies demonstrated progressive apatite layer formation on composites, especially at 16 and 24 wt.% nHA, confirming enhanced bioactivity. Overall, the results establish that PEEK–nHA composites, particularly at 16 wt.% reinforcement, offer an optimal combination of mechanical strength, wear resistance, thermal stability, and bioactivity, making them promising candidates for orthopedic and dental implant applications.