Composting Performance of l-Poly(lactic acid), d-Poly(lactic acid), Their Blends, and Stereocomplex PLA Films

Abstract

Single-use plastics are a major contributor to the generation of plastic waste. Biodegradable polymers provide some hope of curbing this emerging waste issue, with polylactic acid being a promising example. This study examined the biodegradation of l-poly(lactic acid)-PLLA, d-poly(lactic acid)-PDLA, various blends of PLLA and PDLA, as well as a sample of sc-PLLA/PDLA-50-50-A annealed for 30 min to induce crystallization. A simulated study in a lab-scale direct measurement respirometer compared the abiotic and biotic degradations of the various films in compost. The films' crystallinity increased at the beginning of degradation before plateauing. The molecular weight (M _W) decreased first due to hydrolysis from about days 30 to 60, depending on the film, and then due to biodegradation when the microorganisms were able to assimilate the oligomers after it was broken down sufficiently by hydrolysis. By 120 days, the percent biodegradation of the annealed sc-PLLA/PDLA-50-50-A was greatest, at 97%, followed closely by the PLLA/PDLA 50-50 blend at 86%, while PDLA biodegraded the least, at only 40%. Scanning electron microscopy micrographs obtained for all films from day 0 up to day 60 clearly show the erosion of the films over the experiment's progression. These findings showcase the potential of stereocomplex PLA as a biodegradable plastic alternative and support the pursuit of complementing or replacing traditional petrochemical-based plastic options.