Integrated statistical optimization of hydroxyapatite injection molding for biomedical scaffold applications

• A comprehensive investigation on optimizing hydroxyapatite (HA) injection molding using a dual eco-friendly binder system of palm stearin and polyethylene was presented. • Processing parameters were numerically optimized via numerical strategy employing RSM and ANOVA, enhancing the physicomechanical properties of HA. • The optimized HA ceramics exhibited improved microstructural integrity and bioactivity, underscoring their suitability for biomedical applications. This study presents an in-depth statistical approach to optimizing the ceramic injection molding and sintering process of hydroxyapatite (HA), utilizing a dual green binder system composed of water-soluble polyethylene and palm stearin. It aims to assess the effectiveness of conventional sintering in producing high-quality HA sustainably. The CIM technique holds significant promise for the fabrication of hydroxyapatite scaffolds intended for orthopedic implants and prosthetic applications. Given the challenges in achieving optimal mechanical properties in CIM-processed ceramics—due to the high sensitivity of these properties to processing parameters—this study applies a statistical optimization approach using Response Surface Methodology (RSM) and Analysis of Variance (ANOVA) to refine key parameters. RSM was used in determining optimum conditions, including sintering temperature, time, and injection pressure. The RSM results demonstrated that the optimal green body properties—density (2.13 g/cm³) and flexural strength (12.29 MPa)—were achieved at 56 vol.% powder loading, 150 °C injection temperature, and 1.2 MPa pressure. Post-sintering analysis revealed that sintering temperature and its interaction with time significantly influenced flexural strength and hardness, with temperature exerting a greater impact on elastic modulus. The optimal sintered values of the HA part were 20.13 MPa (flexural strength), 4.74 GPa (elastic modulus), and 7.09 GPa (hardness). The improved strength and biocompatibility of the sintered part validate the effectiveness of statistical optimization in overcoming mechanical engineering challenges and highlight its suitability for biomedical scaffold applications.