Preparation and tribological properties of chitosan/hydroxyapatite composite coatings applied on ultra high molecular weight polyethylene substrate

Abstract

We prepared a chitosan/hydroxyapatite composite as coating on ultra–high-molecular-weight polyethylene substrates. The hydroxyapatite was prepared by a precipitation method obtaining particles with nanometer sizes with needle and spherical morphologies. The coating was prepared by a mixture of hydroxyapatite and lower molecular weight chitosan. Fourier transformed infrared spectroscopy technique was used to study the hydroxyapatite synthesis and composite coating. The chitosan/hydroxyapatite coating has been compared with a pure chitosan coating on ultra–high-molecular-weight polyethylene substrate in order to study the influence of hydroxyapatite incorporation. The characterization of coating thickness was performed by light microscopy, whereas the surface morphology was characterized by scanning electron microscopy. A ball-on-disc tribometer, employing a 6-mm diameter tungsten carbide ball, was run as a test method to investigate tribological behaviors of the chitosan/hydroxyapatite and chitosan coatings in dry conditions. It was found that the friction coefficients of the chitosan/hydroxyapatite coating have lower values than chitosan coating. The chitosan/hydroxyapatite coating exhibited lower wear rate values than the chitosan coating. The incorporation of hydroxyapatite nanoparticles into chitosan increased the coating thickness from 20 µm to 37 µm. We have found a composite hardness of 9.1 HV and 6.4 HV for the chitosan and chitosan/hydroxyapatite coating, respectively.