Effect of PLA grades and morphologies on hydrolytic degradation at composting temperature: Assessment of structural modification and kinetic parameters

The present work focuses on a study of the hydrolysis process of different commercial grades of polylactic acid (PLA). The aim was to evaluate the fundamental factors affecting hydrolysis in aqueous medium at 58 °C, namely the temperature indicated by the international standards for biodegradation during composting, and the kinetic constant of the reaction involved in such process. We analyzed samples of PLA with different d-isomer content, having amorphous and semi-crystalline structures. The hydrolysis process was followed, as function of the time, by means of different techniques: pH variation, variation of weight (%) of samples, crystallinity degree using DSC analysis, FTIR and WAXD investigation, molecular weights and molecular weight distribution by GPC analysis. The experimental data were used to describe the kinetic of hydrolysis phenomenon, assuming an autocatalytic mechanism.