Effect of exposure of phosphate buffered saline solution on creep behavior of polylactic acid: in-situ testing and modeling

In this study, a custom immersion creep tester was developed to investigate the in-situ creep behavior of polylactic acid (PLA) in contact with phosphate buffered saline (PBS) solution at various temperatures. Hydrolysis in PBS accelerated creep strain and shortened the lifespan compared to air. The elevated temperatures further facilitate molecular mobility and hydrolysis, leading to faster degradation in PBS environments. The failure mechanisms varied depending on the media, with brittle failure predominating in air and surface hydrolysis accelerating the failure in PBS. The Larson-Miller parameter (LMP) effectively predicted the long-term creep behavior of PLA by incorporating the time-temperature-environment correlation and showed high accuracy. These results highlight the important role of environmental factors in determining the structural integrity and mechanical properties of PLA and emphasize the need to carefully consider environmental conditions when designing PLA-based materials for applications such as biomedical implants or packaging.