Nanocomposites composed of cellulose nanofiber (CNF) and polylactic acid (PLA)
were prepared using a solvent casting method, with the goal of making green
nanocomposites. Prior to the incorporation of CNF into the polymer matrix, surface
modification of CNF was accompanied by esterification to improve the dispersion of
CNF and its interfacial adhesion with the biopolymer. Microstructure, barrier,
mechanical and thermal properties of the nanocomposites were studied. Scanning
electron microscopy (SEM) micrographs revealed uniform distribution of nanoparticles
in the polymer matrix at low contents (1 and 3 wt%), but also that a higher content (5
wt%) of CNF was easily agglomerated. This caused the mechanical properties of the
nanocomposites to be reduced. The results of water vapor permeability (WVP) tests
showed that the use of acetylated nanofibers had no significant effect on the
permeability of films. Tensile strength (TS) and elastic modulus (EM) of
nanocomposites with 1 wt% CNF did not show significant changes, however
elongation percentage (E) increased by more than 60%. The TS, EM and E changed
significantly for nanocomposites with 3 and 5 wt% CNF. Moreover, nanofiber
orientation effectively occurred in the PLA matrix. The reinforcing effect of CNF
composition with PLA caused a slight increase in glass transition and melting
temperatures. However, the nanocomposite films showed a very similar pattern of
thermal behavior to that of neat PLA film.