Evaluating the Thermal Properties and Compatibility of High-Density Polyethylene Micro/Nano-Hydroxyapatite Composites for Advanced Material Applications

This study investigates the thermal behaviour and compatibility of high-density polyethylene (HDPE) composites reinforced with micro- and nano-scale hydroxyapatite (HA) particles, aiming to optimise their application in biomedical environments. Comprehensive thermal analyses were conducted using Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) to evaluate the influence of HA fillers on thermal stability and crystallisation behaviour. TGA results revealed that HDPE/micro-HA composites exhibit enhanced thermal stability, with decomposition initiating at approximately 300 °C and concluding near 450 °C. Micro-HA demonstrated superior performance in delaying degradation compared to nano-HA, attributed to its larger particle size and chain mobility restriction. DSC analyses indicated that while the melting temperature (Tm) remained relatively unchanged, crystallinity was notably affected by HA concentration. The crystallinity increased at optimal filler loadings—specifically, 5wt% micro-HA and 1wt% nano-HA—before declining at higher concentrations. These findings suggest that HA fillers, particularly when appropriately optimised, can enhance the thermal resilience and structural organisation of HDPE composites. The study contributes to the advancement of thermally stable and biocompatible polymer-ceramic systems, reinforcing their potential for biomedical applications such as orthopaedic implants and bone scaffolds.