Usually, SEM images are used to study surface morphology of
a material.
SEM images of both surface and surface and crosssection
of the agar and agar/clay nanocomposite films are shown
in Figure 3.
The SEM observations of cross-section allow, to some
extent, explanation of the differences in mechanical properties of
the films (Phan and others 2005), that is, the better mechanical
properties of agar and agar/Cloisite Na+ nanocomposite film is
expected due to its more compact and homogeneous structure
compared to those of agar/Cloisite 30B and agar/Cloisite 20A
nanocomposite films.
The SEM images of film surface indicate
clay particles are relatively well dispersed in the polymer matrix and they also show that the neat agar film has smoother surface than the other nanocomposite films.
So, AFM images were used to study detailed structure of the surface of film samples.
The 3D AFM images are shown in Figure 4.
The 3D images clearly show the difference in surface roughness between films. The average
(Ra) and root mean square roughness (Rq) of the film samples
are shown in Table 3.
This result indicates the surface roughness is dependent on the clay types used. Though it is not statistically
significant, the surface roughness of agar/Cloisite Na+ nanocomposite
film increased slightly, while the other 2 nanocomposite
films composited with organoclays significantly (P < 0.05) increased
in the surface roughness.
This may be also attributed to the compatibility between nanoclay and polymer matrix.