Novel nanocomposites based on fatty acid modified cellulose nanofibers/poly(lactic acid): Morphological and physical properties

• Surface modification of cellulose nanofiber (CNF) by using oleic acid increases the hydrophobicity of esterified CNFs.
• Modified CNF (MCNF) exhibits lower decomposition temperature and degree of crystallinity.
• Surface treatment improves the compatibility of CNFs with PLA matrix.
• Addition of MCNF improves the barrier, thermal and mechanical properties of PLA based nanocomposites.

A novel poly(lactic acid) (PLA) based nanocomposite, reinforced by cellulose nanofibers (CNFs) was prepared. CNFs were previously treated by oleic acid for improving the compatibility with PLA matrix. Resulted modified nanofibers (MCNFs) exhibited reduced surface polarity in comparison to non-modified CNFs. MCNFs were subsequently introduced into PLA matrix and the effects of the CNFs surface modification on morphological, mechanical, thermal and barrier properties of the PLA based nanocomposites were studied. The morphology of fracture surfaces was evaluated by field emission scanning electron microscopy (FE-SEM). Differential scanning calorimetry (DSC) showed that the melting temperatures of the PLA–MCNF nanocomposites were considerably higher than that of the pure PLA film. The ultimate tensile strength and Young's modulus of nanocomposites (at 12% MCNFs) were about 2.5 and 2 times as much as those of the pure PLA films, respectively. In addition, adding MCNFs caused a decrease in water vapor permeability.