Fig. 2a and b shows typical topographic images of PLA composites
containing silane treated and untreated cellulose nanofibers.
The comparative observation of these figures shows a better dispersion
in the case of PLA composite containing CNFS. Several areas
with CNF agglomerations marked with red circles (light grey in
printed version) and individual nanofibers covered by the polymer
(marked with black arrows) can be observed in Fig. 2a. A
distinct improvement of the dispersion quality is observed when
the nanofibers are silane treated (Fig. 2b). CNFS are more uniformly
distributed on the surface of PLA/CNFS composite and less agglomerated
fibers can be seen in Fig. 2b as compared to Fig. 2a. Most
of CNF agglomerates are located at the surface of the material as
opposite to CNFS which are located deeper in the polymer, suggesting
a better cellulose fiber–matrix interface in the second case.
Moreover, a different maximum height must be noted in the analyzed
images: 27.3 nm for PLA/CNF and only 16.2 nm for PLA/CNFS
confirming the deeper location in the matrix and the better adhesion