Preparation of High-Toughness Cellulose Nanofiber/Polylactic Acid Bionanocomposite Films via Gel-like Cellulose Nanofibers

This study demonstrates a procedure for preparing gel-like cellulose nanofibers (CNFs) in polyethylene glycol (PEG) to toughen polylactic acid (PLA) nanocomposite films. A well-dispersed solution of CNFs in ethanol was produced from microcrystalline cellulose by using a high-pressure microfluidizer. The fiber diameter of CNFs was found to be in the range of 80–100 nm. Ethanol was replaced by PEG using a rotary evaporator to obtain gel-like CNFs/PEG. PLA/PEG/CNF films were prepared using the solvent casting method, with the CNF content varying from 0.15 to 5 phr. The effect of CNFs on the mechanical, morphological, and thermal properties of PLA nanocomposite films was investigated. The results demonstrate that the addition of CNFs improved Young's modulus and toughness of PLA/PEG films. In contrast, a slight decrease in mechanical properties was observed when the content of CNFs reached 0.83 phr. Considère's constructions are used to explain the neck phenomena and cold drawing of nanocomposite films. The crystallization and thermal stability of PLA nanocomposite films were enhanced, with a slight decrease in cold-crystalline temperature (Tcc) and an increase in decomposition temperature (Td).