Investigation on tribological behaviour of poly (methyl methacrylate) biocomposite containing hydroxyapatite

PMMA, a thermoplastic polymer, is widely used in biomedical applications like bone cement. However, it is known to have low wear resistance. To enhance its tribological behavior, a reinforcement phase is necessary. For this purpose, in this study, homemade hydroxyapatite (HAp) was utilized to enhance the mechanical properties and wear resistance of PMMA, while also increasing its biocompatibility. The HAp was reinforced into the PMMA matrix to enable its use under load. Using the thermal extraction method, natural raw materials were used to successfully synthesize homemade HAp powder. The powder's elemental composition was determined using an X-ray fluorescence spectrometer (XRF). The d0.5 of HAp powders in particle size analysis was 7.464 µm. Hot isostatic pressing was used to create PMMA-HAp biocomposites with various HAp rates (5%, 10%, and 15% wt.) in the PMMA (HIP). The wear morphology was characterized by scanning electron microscopy (SEM). The SEM images showed a severe abrasive wear mechanism, but a relatively stable wear surface was observed that indicated slight abrasion during the wear tests with the increase of HAp ratio. The wear tests were carried out with a ball-on-disc system under dry environment conditions at sliding speed between 0.5-1.0 m/s and loads of 10-20-30 N. The highest wear rate was obtained in 15% HAp reinforced PMMA with a sliding speed of 1.0 m/s and value of 4.72x10-4 mm3/Nm under 20 N load. The HIPed densities of the samples increased from 1.15 to 1.31 g/cm3 with increasing the amount of HAp. Similarly, the Vickers test results showed that the hardness values increased from 14.76 Hv to 22.03 Hv.