Thermal behavior, crystallinity, mechanical performance, and degradation of PLLA/PGA blends for biodegradable implant applications

This study investigates the thermal behavior, mechanical properties, and degradation characteristics of poly(L-lactic acid) (PLLA), polyglycolic acid (PGA), and their immiscible blends to explore their potential for biodegradable implant applications. Differential Scanning Calorimetry (DSC) revealed that pure PLLA exhibited the stable α-phase crystals. Pure PGA showed a sharp melting peak reflecting its high crystallinity. Interestingly, the PLLA/PGA 75/25 blend displayed only a single melting peak at 175°C, accompanied by a new exothermic event at 160°C, attributed to the transition of metastable α' crystals to the stable α-phase. This suggests partial compatibility and disrupted PLLA crystallization. At higher PGA contents (50% and 75%), two distinct melting peaks appeared, indicating phase separation and immiscibility. Mechanical testing correlated with the thermal transitions, where the 75/25 blend exhibited the highest flexural strain, suggesting enhanced ductility due to α' phase formation. In contrast, increased PGA content resulted in higher modulus and strength, driven by PGA’s crystalline reinforcement. Degradation studies revealed that PGA-rich blends degraded faster and induced significant pH reductions, while PLLA exhibited slow degradation. The results demonstrate that PLLA/PGA blends offer tunable mechanical performance and degradation profiles through composition adjustment, providing a pathway to develop biodegradable implants with controlled resorption rates and mechanical adaptability.