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Plasma activation of polyetheretherketone (PEEK) surfaces and the influence on coating formation in a supersaturated calcium phosphate solution was investigated in this study. It was observed that plasma treatment in a N2/O2 plasma had a significant effect on the wettability of the PEEK surface. The contact angle decreased from 85 degrees to 25 degrees after plasma treatment. Cell culture testing with osteoblastic cell lines showed plasma activation not to be disadvantageous to cell viability. X-ray photoelectron spectroscopy (XPS) analysis was performed to characterize the chemical composition of the PEEK surfaces. It was observed that the O1s intensity increased with plasma activation time. At the C1s peak the appearance of a shoulder at higher binding energies was observed. Coating of PEEK was performed in a supersaturated calcium phosphate solution. Coating thicknesses of up to 50 microm were achieved after 24 days of immersion. Plasma activation followed by nucleation in a highly saturated hydroxyapatite solution had a positive effect on the growth rate of the layer on PEEK. Chemical analysis revealed that the coating consists of a carbonate-containing calcium phosphate.

Plasma-spraying of metallic implant surfaces is an established method for the application of hydroxylapatite (HA) coatings. Carbon fibre reinforced thermoplastics show different thermal and mechanical properties, compared with titanium substrates. In this paper first results of the influence of the established coating method on carbon fibre reinforced thermoplastics are presented. First investigations of the tensile adhesion strength, tested with a newly developed testing device, showed that the adhesion between the HA coating and the carbon fibre reinforced polyetheretherketone (PEEK) composite is very low. Macromechanical bending tests showed a change to initial tensile instead of compression failure of the coated composite substrate. Micromechanical bending tests in a scanning electron microscope (SEM) hot tensile stage (Raith GmbH) revealed crack propagation within the ceramic coating and in the coating-substrate interface before the total failure of the composite substrate occurred.