transparency related to G and interaction effect is negligible.
According to ANOVA, the p-values for C, G and C G are 0.0036,
0.1203 and 0.9197, respectively, indicated that only Na–MMT content
is a significant parameter in correlated model. The final equation
in terms of actual factors is presented in Table 3. Response
surface for the transparency of the nanocomposites as a function
of glycerol and nanoparticles content is presented in Fig. 3.
3.5. UV–visible spectra
Fig. 4 indicates the transmission of some of the starch- Na–MMT
films. In Fig. 4a, all samples have no transmittance for wavelengths
less than 216 nm. Control film (30% glycerol and 0% clay) in the UV
range between 216 and 266 nm showed transmittance while the
addition of a very low amount (2.5% and 5%) of Na–MMT decreased
UV transmission to almost zero. It indicates that almost all UV light
was absorbed. The Wavelength between 266 and 400 nm, both of
films containing Na–MMT have lower transmittance than control
film. In addition, G30C2.5 and G30C5 has almost the same behavior.
The UV filtering of Na–MMT is considerable for part of UV range
(400 nm), all the
films became more transparent. The differences in transmittance
between G30C2.5 and G30C5 samples were increased by increasing
the wavelength. As shown in Fig. 4b, the effects of glycerol in transmittance
of both of UV and visible ranges have the same pattern. By
the increase in glycerol content, prepared film become more transparent.
The difference between transmittances will increase by an
increase in wavelength. By increasing the wavelength, the effect
of Na–MMT content on the transmittance became more significant.
Therefore, transmittance at high wavelengths could be used as an
easy method to investigate the uniform distribution of nanoparticles
in biopolymer. Mixture of glycerol and starch solution is
homogenous and shall be considered that in any parts of the