Structural and mechanical properties of biodegradable poly(lactic acid) and pectin composites: using bionucleating agent to improve crystallization behavior

摘要

Biocomposites of poly(lactic acid) (PLA) and pectin, which are low-cost organic materials, were prepared using an internal mixing machine in various pectin contents, i.e., 2, 4, 6 and 8% w/w. When pectin was added as a nucleating agent, the mechanical properties of the biocomposites, such as tensile and impact testing, were considerably improved, particularly following the annealing process. In addition, the PLA-pectin annealed at 4% w/w showed the highest strength and thermal stability. This can be explained by the fact that PLA containing 4% pectin by weight had the best dispersion, as indicated by scanning electron microscopy (SEM) and synchrotron-based 2D chemical mapping FT-IR. Moreover, pectin not only serves as a reinforcing material to improve mechanical characteristics but also aids in the crystallization of PLA, which was confirmed by in situ synchrotron-based wide-angle X-ray scattering (SR-WAXS). The crystallization rate and crystallinity were maximum at 8% w/w pectin addition according to the SR-WAXS results. This shows that pectin dispersion is the most important factor in determining the mechanical and thermal properties of biocomposites.