Degradation kinetics of thermo-oxidized poly (lactic acid) biocomposites under composting conditions

This research studied the effect of composting incubation time on the physicochemical properties of previously thermo-oxidated multiscale composite materials (MCMs) based on polylactic acid (PLA), cellulose microfibers and cellulose nanocrystals. The MCMs were prepared by extrusion and subsequently divided into two groups: with and without thermo-oxidative treatment. Both groups were subjected to composting over a period of 180 days in a rotary drum composter. At specific intervals, samples were withdrawal and their physicochemical properties were characterized. The results indicate that the incorporation of cellulose microfibers (MFC) enhances the crystallinity of PLA; this enhancement was significantly greater in the thermo-oxidized materials. However, the DSC results showed a progressive decrease in their crystallinity was observed with increasing incubation time. Micrographs suggest that the presence of MFC promotes surface biodeterioration of the material. FTIR analysis revealed the appearance of a broad band in the 3100–3300 cm −1 region, attributed to the formation of a biofilm on the sample surfaces. Furthermore, the thermogravimetric analysis (TGA) showed the thermo-oxidative treatment and the incubation time intensifies the thermal stability of the MCMs.