Effect of Interfacial Treatment and Tensile Drawing on Mechanical Properties of Tricalcium Phosphate/Poly(lactic acid) Composite

In recent years, biodegradable composites have attracted attention as alternatives to metallic materials for bone fixation devices, which are prone to corrosion, fatigue, and stress shielding. In this study, a hybrid approach combining interfacial treatment and tensile drawing was investigated to enhance the mechanical properties of tricalcium phosphate (TCP)/poly(lactic acid) (PLA) composites. The surface of TCP, a bioactive ceramic, was modified with L-lactic acid or stearic acid to improve interfacial adhesion with PLA. Composite specimens of interfacial treated TCP and PLA were prepared by kneading and compression molding. Among the two agents, L-lactic acid did not improve tensile strength and fracture strain of TCP/PLA composite, whereas stearic acid enhanced both properties. At a stearic acid amount of 6 phc (per hundred ceramics), the tensile strength and fracture strain reached the maximum values of approximately 1.5 times and 1.6 times those of the untreated specimen, respectively. Infrared spectroscopy revealed no peak shifts indicative of hydrogen bonding between the modified TCP and PLA. In contrast, fracture surface observations showed a fibrillar structure between TCP and PLA only at 6 phc, suggesting bond formation. Subsequently, the interfacial treated TCP/PLA composite specimens were tensile drawn to induce molecular orientation. The hybrid approach yielded superior mechanical properties compared to either treatment alone, demonstrating a synergistic effect of interfacial treatment and drawing.