The Key to Increasing the Elongation of Poly (<sc>l</sc>-Lactic Acid) Monofilaments in Hydrothermal Environment-Dislocation Slip

Biodegradable polymers such as poly (l-lactic acid) (PLLA) have extensive applications in the clinical and medical areas due to their superior mechanical properties. When applied in implantable medical devices, PLLA will inevitably face the challenge of a 37 degrees C liquid environment that can affect its mechanical performance. This study mainly explores the impact of temperature-water synergy on PLLA monofilaments. The combined effects of temperature (25 degrees C-65 degrees C) and the water environment are systematically studied, especially for the 37 degrees C liquid medium simulating the human body. It was found that the mechanical properties of PLLA monofilaments got worse with the increase of temperature or the immersion of water molecules but improved in a 37 degrees C liquid environment, especially for the elongation at break. By scanning electron microscopy (SEM) and wide-angle X-ray scattering (WAXS) analysis, it is believed that the key to increasing the elongation in 37 degrees C liquid environment is the extensive occurrence of dislocation slip. This study has provided further understanding of the intrinsic connection between the mechanical properties and structural changes of PLLA monofilaments, which is crucial for the application in medical devices.