Degradation of Poly(Lactic Acid) under Simulated Landfill Conditions

Abstract

In this study, the physical and chemical properties change of poly (lactic acid) after being buriedin the mixture of soil and sludge under thermophilic (61 °C) oxygen limited conditions were investigated using various analytical techniques. The environmental factors under these setting conditions and microbial activities accelerated the degradation process of PLA. Under tested conditions, PLA lost their weight about 90% at the 90 days burial period. During the degradation process, PLA samples were continuously broken to small fragile fragments and showed the size less than 1 mm at the end of the degradation test. The change of the surface morphology was revealed by Scanning Electron Microscopy (SEM). Many pores, cracks and irregular roughness were presented on the PLA surface. Thermal decomposition was decreased from 387.8 °C to 289.2 °C. The percentage of carbon content in molecular structure decreased from 49.46% to 45.42%. In addition, the Fourier transformed infrared spectroscopy (FTIR) revealed the change of ester bonds. This study can be used to develop the PLA waste management process.