Crystallization behavior studied by synchrotron small-angle X-ray scattering of poly (lactic acid)/cellulose nanofibers composites

In this study, synchrotron small angle X-ray scattering (SAXS) technique was applied to study the crystallization behavior of poly (lactic acid) (PLA)/cellulose nanofibers (CNFs) biocomposites. Morphological properties of the biocomposites were elucidated as well. PLA/CNFs biocomposites were prepared by melt mixing in an internal mixer. Glycidyl methacrylate (GMA) grafted poly (lactic acid) (PLA-g-GMA) was used as a compatibilizer between CNFs and PLA. CNFs were extracted from cassava pulp (CP) by acid hydrolysis method. Effect of CNFs content on the crystallization behavior of the biocomposites was studied. The SAXS results showed that with the addition of 0.1 wt% CNFs and using PLA-g-GMA as a compatibilizer, the crystallization rate of biocomposites significantly increased. The paracrystalline model was applied and well fitted to the SAXS data. The average long period (L) and lamellar thickness (Lc) determined by applying the paracrystalline model of PLA, PLA-g-GMA, and PLA/PLA-g-GMA/CNFs biocomposites exhibited a slight decrease in the very early stages of crystallization, then become time independent. The fiber content of 0.1 wt% was found to give the highest crystallization rate of both PLA/CNFs and PLA/PLA-g-GMA/CNFs biocomposites. The enhanced interfacial adhesion between PLA and CNFs by PLA-g-GMA was confirmed by scanning electron microscopy (SEM).