Thermal degradation of poly(lactic acid) measured by thermogravimetry coupled to Fourier transform infrared spectroscopy

Thermal decomposition of poly(lactic acid) (PLA) has been studied using thermogravimetry coupled to Fourier transform infrared spectroscopy (TGA-FTIR). FTIR analysis of the evolved decomposition products shows the release of lactide molecule, acetaldehyde, carbon monoxide and carbon dioxide. Acetaldehyde and carbon dioxide exist until the end of the experiments, whereas carbon monoxide gradually decreases above the peak temperature in that the higher temperature benefits from chain homolysis and the production of carbon dioxide. A kinetic study of thermal degradation of PLA in nitrogen has been studied by means of thermogravimetry. It is found that the thermal degradation kinetics of PLA can be interpreted in terms of multi-step degradation mechanisms. The activation energies obtained by Ozawa-Flynn-Wall method and Friedman's method are in good agreement with that obtained by Kissinger's method. The activation energies of PLA calculated by the three methods are 177.5 kJ mol(-1), 183.6 kJ mol(-1) and 181.1 kJ mol(-1), respectively.