JEC COMPOSITES MAGAZINE - Issue #134 - May/June 2020 - 49

Sustainable food packaging materials using bionanocomposite films

of the bionanocomposites, by
20 and 4%, respectively. The
highest improvement in Young's
modulus was 148% in the bionanocomposites reinforced with 1
wt.% HNTs as opposed to that of
the polymer blends. An evident
reduction in the tensile strength
and Young's modulus of the bionanocomposites was detected
beyond 1 wt.% HNTs, which was
attributed to the typical agglomeration effect of nanofillers. On
the other hand, the elongation at
break of the bionanocomposites
consistently declined at HNT
contents of 0.5-5 wt.%, mainly
due to the inclusion of HNTs as
rigid nanofillers to reduce the
brittleness of the corresponding
bionanocomposites.
Water resistance
Water resistance is crucial for
food packaging materials because
of its effect on the shelf life of
foodstuffs, as well as a high water
solubility of PVA as a base polymer in the prepared bionanocomposite films. Relatively high
Wa and Ws were manifested in
the PVA/ST/GL blends due to
the typical water-soluble characteristic of all the constituents.

When increasing the HNT content from 0 to 5 wt.%, the Wa and
Ws of the bionanocomposites decreased more or less in a monotonic manner by 44.2 and 48.0%,
respectively, as illustrated in Figure 2. The enhanced water resistance of the bionanocomposites
arose from the relatively high hydrophobicity of HNTs as well as
their dispersion to generate more
tortuous paths when compared
to those induced by PVA/ST/
GL blends. It was worth noting
that the further reduction of the
Wa and Ws of the bionanocomposites beyond 1 wt.% HNTs
appeared to be insignificant,
which may result from nanofiller
agglomeration.
Barrier properties
Most polar polymers, such as
PVA, have good gas barrier properties (i.e. low gas permeability),
but poor water barrier properties
(i.e. high WVP) due to the presence of a large number of free
hydroxyl groups occupied by permeable water molecules. When
increasing the HNT content
from 0 to 5 wt.%, the WVP, oxygen and air permeabilities significantly declined by 73.5, 74.8 and

Fig. 3: Barrier properties of PVA/ST/GL blends and their
bionanocomposites at different HNT contents [18]

Fig. 4: (a) Digital images before and after the biodegradation tests;
and (b) biodegradation rates of PVA/ST/GL blends and
their bionanocomposites at different HNT contents [17]

76.0%, respectively, as evidenced
in Figure 3. This reduction in
bionanocomposite permeability
could be interpreted by the consumption of free hydroxyl groups
by the HNTs to form hydrogen
bonds with the polymer matrices
as well as the creation of tortuous
paths to restrict the diffusion and
penetration of permeable molecules.
Biodegradability
The digital images of different
films before and after 24-week
biodegradation tests revealed
that both the PVA/ST/GL blend
films and the corresponding bionanocomposite films consistently shrank in size and became
more fragile with wrinkling effect
shown in Figure 4(a). The PVA/
ST/GL blends and their bionanocomposites showed a similar
behaviour during the biodegradation tests, which was reflected
by high biodegradation rates for

N°134 May - June 2020

the first three weeks due to a high
microorganism activity and was
then followed by slightly slower
and more constant biodegradation rates with time, as depicted in
Figure 4(b). The polymer blends
had a good biodegradation rate of
56.9% due to the presence of ST
as a completely biodegradable
polymer, while the biodegradation rate of the bionanocomposites reinforced with 1 wt.% HNTs
decreased to 41.3% owing to the
presence of nanofillers to restrict
the infiltration of microorganisms
within the film materials. Nonetheless, such biodegradation rates
of the bionanocomposites tended
to increase modestly to 45.0 and
45.8% at the HNT contents of 3
and 5 wt.%, respectively, possibly
resulting from HNT agglomeration.
Food packaging tests
The relative weight loss rates of
avocados and peaches packed

/ jec composites magazine

JEC COMPOSITES MAGAZINE - Issue #134 - May/June 2020

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #134 - May/June 2020