Microstructure analysis of polylactic acid-based composites during degradation in soil

Biodegradation behavior of biodegradable starch/wood power/polylactic acid (PLA) composites from the natural northeast Chinese soil environment was investigated in this study. The microstructural changes of the materials for 105 days was comprehensively characterized by X-ray diffraction (XRD), Differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR). XRD results showed that the crystallinity of the composites increased at the initial soil burial period, followed by a decrease during the degradation period. DSC of the surface and interior of the composites at different degradation times further characterized the changes in composite microstructures. After degradation, short molecular chains were formed, which slowly gained various extents of chain mobility. FTIR analysis indicated that the random fracture sites of PLA and starch were C=O and C-O groups, respectively. The absorb intensity of C=O and C-O groups decreased with the prolonged degradation time. The P-S5W5 showed a higher degradation rate than others, likely due to the synergetic effect between starch and wood power.