3.2.1. Morphologies

The morphologies of the ChNF–CNF composite structure were investigated. Figure 4 shows the SEM images of the ChNF–CNF composite and CNF film. Figure 4a shows a smooth surface of the CNF film and Figure 4b is the cross-section SEM image of the CNF film, which exhibits the layer-by-layer structure of CNF. After blending with ChNF, the surface of ChNF–CNF composite turned out to be rough. The cross-section SEM image of the composite also shows a layer-by-layer structure similar to the CNF film. It was shown that the ChNF was well blended with CNF to maintain the layer-by-layer structure.

**Figure 4.** FE-SEM images of: (**a**) surface of CNF film; (**b**) cross section of CNF film; (**c**) surface of ChNF–CNF composite; and (**d**) cross section of ChNF–CNF composite.

In addition, to consider ChNF–CNF composites for packaging, the composites should be bendable. Thus, a quick bending test was performed with the ChNF–CNF composite. The composites were so flexible that they could be bent in any direction without cracking. The thickness of the composites was in the range of 40–50 μm. Figure 5 shows flexibility of the composite in bending and rolling deformation.

**Figure 5.** Flexibility of ChNF–CNF composite by: (**a**) bending; and (**b**) rolling.
