Characterization of the time and temperature dependent mechanical properties of Poly (Lactic acid) (PLA)

This study examines the stress relaxation behavior and master curve generation of Poly (Lactic Acid) (PLA) and Poly (Lactic Acid) (PLA)/Hydroxyapatite (HA) nanocomposites across various temperatures. PLA is a biodegradable and biocompatible polymer commonly used in biomedical applications, including fracture repair, interference screws, suture anchors, and meniscus repair. Hydroxyapatite serves as a reinforcement to enhance PLA's mechanical properties. The study investigates the impact of temperature on strain relaxation in PLA/HA nanocomposites and the creation of a master curve. Uniaxial tensile tests were performed at temperatures of 23, 30, 35, 40, 45, 50, and 55 °C at a loading rate of 1 mm/min, with samples loaded to a strain level of 1.5%. A 20-minute strain relaxation test was then applied at this strain level. Using the obtained relaxation data, master curves for PLA and PLA-HA composites were constructed by referencing data at various temperatures (23 °C, 40 °C, and 55 °C) and comparing shift factors.