Fabrication and characterization of an electrostatically bonded PEEK- hydroxyapatite composites for biomedical applications.

In this study, it was aimed to produce electrostatically induced polyetheretherketone (PEEK) and strontium substituted hydroxyapatite (SrHA) composites. SrHA nanoparticles (5 and 10 vol%) were introduced in the PEEK matrix to increase its mechanical properties and osseointegration. In order to disperse and homogeneously distribute the nanoparticles within the matrix, an electrostatic bond was developed between the PEEK and nanoparticles by wet processing through the attraction of the oppositely charged particles. Particles were pressed and sintered according to the Taguchi Design of experiments (DoE) array. The effects of SrHA reinforcement, sintering temperature and time on the density, crystallinity and crystallite sizes were determined with density test, DSC and XRD, respectively. The disks were also analyzed via SEM, FTIR, compression, microhardness, and nanoindentation tests and were immersed into the simulated body fluid (SBF). The composites produced from electrostatically induced powders presented a homogenous microstructure as SEM analysis illustrated the homogenous dispersion and distribution of the SrHA nanoparticles. The SrHA nanoparticles decreased the relative density and crystallinity of the composite, whereas, the rise in the sintering temperature and time enhanced the relative density, according to the DoE results. SrHA reinforcement improved the reduced modulus and nanoindentation hardness of the PEEK (348.47 MPa, 5.97 GPa) to 392.02 MPa and 6.65 GPa, respectively. SrHA promoted the bioactivity of the composite: an apatite layer covered the surface of PEEK/10SrHA composite after 14 days incubation. These promising results suggest that the electrostatically bonded composite powders would be used to produce homogenous PEEK based bioactive composites.