Mechanical Properties of Polyetheretherketone Composites with Surface-Modified Hydroxyapatite Nanofibers and Carbon Fibers

Abstract

Though carbon fiber (CF)-reinforced polyetheretherketone (PEEK) has gained attention as an alternative to metallic orthopedic implant materials by virtue of its good biocompatibility and favorable mechanical properties, its applications are limited due to its bioinertness and hydrophobicity. Hydroxyapatite (HA) incorporated to address the issue has appeared to lower the mechanical strength, often severely, due to the aggregation of HA in the composites. This study aimed to develop a PEEK composite with HA and CF whose mechanical properties are comparable to those of human cortical bone. We synthesized and incorporated HA nanofibers (HANF) to improve the mechanical properties of the composite to take advantage of the high aspect ratio and bridging effect of the fibers. In addition, the HANF and CF were modified with a silane coupling agent to enhance their interfacial adhesion with the PEEK matrix. The results showed that incorporating the modified HANF (m-HANF) and the modified CF (m-CF) effectively improved the mechanical properties compared to those of neat PEEK and composites with unmodified fillers. Mechanical properties comparable to those of the cortical bone were observed in PEEK/m-HANF/m-CF composites of various compositions. The improved dispersion of the HANF and enhanced interfacial adhesion of m-HANF and m-CF with the PEEK matrix were also observed in the X-ray tomography microscope system (XRM) and scanning electron microscopy (SEM) results. This unique PEEK/m-HANF/m-CF composite can yield an effective design strategy for developing high-performance PEEK biocomposites.