Processing and Properties of Hydroxyapatite Whisker Reinforced Polyaryletherketones for Orthopaedic Applications

The overall objective of this study was to produce hydroxyapatite (HA) whisker reinforced polyaryletherketone (PAEK) biocomposites and scaffolds with tailored mechanical properties similar to those of bone tissue. The effects of the reaction temperature and carboxylic acid on the morphology and composition of HA whiskers synthesized by chelate decomposition were first studied using a controlled heating rate under static conditions. Reaction temperature affected both whisker composition and morphology, while the carboxylic acid used as the chelating agent affected whisker morphology. Polyetheretherketone (PEEK) was reinforced with up to 50 vol% HA whisker reinforcement using a novel powder processing and compression molding technique. Composites with 40-50 vol% HA whisker reinforcement exhibited elastic moduli similar to that of human cortical bone in the longitudinal direction. Composites with 10 and 20 vol% HA whisker reinforcement exhibited tensile strengths similar to that of human cortical bone in the longitudinal direction. HA whisker reinforced polyetherketoneketone (PEKK) scaffolds were successfully processed with 75-90% porosity and 20-40 vol% HA whisker reinforcement. The compression molding/particle leaching technique used in this study facilitated the incorporation of high levels of bioactive HA whisker reinforcements into the polymer matrix. Micro-CT indicated interconnected porosity in the size range required for bone ingrowth. The mechanical properties of HA whisker reinforced PEKK scaffolds were investigated in uniaxial compression. Scaffolds processed at 375Ìâå¡C with 75% porosity and 20 vol% HA whisker reinforcement exhibited an apparent modulus of 141 MPa and an apparent yield strength of 2.3 MPa. These values fall within the ranges reported for the modulus and strength of trabecular bone.