Exploring the Tribological Behavior and Surface Characteristics of Polymethyl-Methacrylate/Hydroxyapatite (PMMA/HA) Composites: Investigating the Effect of Hydroxyapatite Weight Ratios on Wear Performance, Surface Roughness, and Hardness

Abstract

This study conducts an analysis of the tribological characteristics of polymethyl-methacrylate (PMMA) composites reinforced with varying weight ratios of hydroxyapatite (HA) nanoparticles. It encompasses a systematic assessment of both hardness and surface roughness using the Shore-D hardness testing method and profilometer measurements, respectively. The results reveal a correlation between the HA nanoparticles weight ratio and hardness, indicating an increase in HA nanoparticles weight ratio corresponded to enhanced hardness. Moreover, higher HA nanoparticles weight ratios result in rougher surfaces, impacting composite performance. Specifically, the composite containing 5%-HA exhibited a Rq of 6 µm, which incrementally rose to 6.3 µm for the 10%-HA composite and significantly increased to 11.1 µm for the 15%-HA composite. Increasing HA weight ratios led to higher Rz values: 28 µm for 5%-HA, 35.1 µm for 10%-HA, and 72.5 µm for 15%-HA, indicating greater surface irregularities. The wear rates and friction coefficients are examined under applied forces ranging from 5 to 15 newtons across three distinct HA weight ratios (5%, 10%, and 15%). The results show a decreasing trend in wear rates with increasing weight ratios of HA, evidenced by weight loss rates of 0.0052 gr, 0.0011 gr, and 0.006 gr for samples S.1, S.2, and S.3, respectively, under a 15 N applied force. The friction coefficient analyses highlight complex dependencies on sliding distance, applied force, and HA weight ratio. Statistical tests, such as One-way analysis of variance (ANOVA) and effect size calculations, confirm significant applied force effects on friction coefficients, offering insights for optimizing PMMA/HA composite performance in biomedical applications.