Degradation kinetics and performances of poly(lactic acid) films in artificial seawater

Used poly(lactic acid) (PLA) films as the research object, the degradation kinetics equation was established through the degradation experiments of samples in artificial seawater at 60, 70, 80 and 90 °C, and then the degradation performances of PLA films in artificial seawater at 90 °C were explored. The surface morphology, chemical structure and thermal properties of PLA films after degradation in artificial seawater at 90 °C were studied by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, gel permeation chromatography, differential scanning calorimetry and nuclear magnetic resonance spectroscopy, and the composition of degradation products was also analyzed. The results showed that the degradation of PLA films in artificial seawater conformed to the first-order reaction characteristics. The half-life period of degradation is 12 or 468 days under 90 or 60 °C. With the increase in degradation time, the surface of PLA films became roughness, the characteristic functional groups of the solid degradation products were basically unchanged, the crystallinity increased first and then decreased, while the relative molecular weight and Tm decreased gradually. The oxygen content of the surface of the material and lactic acid content in the degradation filtrate increased gradually. Graphical abstract The degradation kinetics of poly(lactic acid) (PLA) films in artificial seawater was studied. The results showed that the degradation of PLA films in artificial seawater conformed to the first-order reaction characteristics, which provides theoretical guidance for the practical application of polylactic acid-based materials in the marine environment.