Page 47 - PR 2014 2016 10 Materials and Nanotechnology

Materials and Nanotechnology | Progress Report 323

AgNP0.5% showed increase of elongation at Processing starch biodegradable
break above 1000%, which suggests the ap Pro- nanocomposites
cessing starch biodegradable nanocomposites.
Polymer-clay nanocomposites (PCN) based on
Polymer-clay nanocomposites (PCN) based cassava starch, synthetic hectorite clay and
on cassava starch, synthetic hectorite clay inverted sugar cane syrup (plasticizer) were
and inverted sugar cane syrup (plasticizer) prepared by solvent-assisted (casting) process
were prepared by solvent-assisted (casting) producing transparent and homogeneous
process producing transparent and homoge- films. Small amounts of clay (5-15 wt.%) re-
neous films. Small amounts of clay (5-15 wt.%) sulted mainly in exfoliated nanocomposites
resulted mainly in exfoliated nanocompos- while large amounts (30 wt.%) promote the in-
ites while large amounts (30 wt.%) promote tercalated nanocomposites formation. FT-Ra-
the intercalated nanocomposites formation. man bands sensitive to hydrogen bonding
FT-Raman bands sensitive to hydrogen bond- in starch granules are progressively shifted
ing in starch granules are progressively shifted to lower wavenumbers as the clay content
to lower wavenumbers as the clay content is raised. Nanocomposites show a similar
is raised. Nanocomposites show a similar thermal behavior up to 320°C while the bio-
thermal behavior up to 320°C while the bio- molecule decomposition at about 500°C is
molecule decomposition at about 500°C is dependent on the clay content. CO release
2
dependent on the clay content. CO release at at about 300°C (non-oxidative decomposition
2
about 300°C (non-oxidative decomposition of of polymeric chains) decreases if compared
polymeric chains) decreases if compared to the to the gas delivery at ca. 500°C, as the clay
gas delivery at ca. 500°C, as the clay content is content is increased. Films with clay content
increased. Films with clay content higher than higher than 10 wt.% show no substantial
10 wt.% show no substantial benefit for either benefit for either elongation or resistance
elongation or resistance properties, FIG. 54. properties.

PCN materials based on synthetic hectorite
clay and cassava starch were prepared. When
small amounts of clay are added, the XRD data
indicate the formation of mostly exfoliated
nanocomposites, in which individual or few
stacked inorganic layers are dispersed in the
polymer matrix. However, when amounts
of clay higher 10% are added, intercalated
nanocomposites are formed. FT-Raman
spectra indicate that crystallinity of starch
in the hybrid films decreases as the amount
of Laponite is increased, corroborating with
XRD data. Prepared films are transparent and
homogeneous. According to TGA analysis, the
different steps of thermal decomposition are
dependent on the amount of clay in the hybrid
Figure 54. (a/b) . Film process (a) and stress X strain curves (b) for
nanocomposites films. material. The good dispersion of Laponite