Bio-hybrid Nanocomposite Roll-to-roll Coatings for Fiber-based Materials and Plastics - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 199

results good dispersion, especially when the sufficient amount of mixing energy is
used. The degree of exfoliation can be improved by the use of conventional shear
devices such as extruders, mixers, ultrasonicators, ball milling, fluidizators, and so on.
materials aNd methods
Natural polysaccharides (chitosan and pectin) were used as continuous polymeric
matrixes in which an inorganic nanosized material, >98% montmorillonite, was dis-
persed. In order to ensure the sufficiently defoliated and nanosized structure of the
nanoclay platelets, the ultrasonication and high pressure fluidization were used for
homogenization polysaccharide-nanoclay dispersions. Coatings and films were pre-
pared by wet coating of chitosan onto plasma-activated LDPE coated paper (coatings)
and solvent casting of pectin on Petri dishes (films). Oxygen transmission rates were
measured with Oxygen Permeation Analyser Model 8001 (Systech Instruments Ltd.).
The oxygen transmission tests were carried out at 23°C and 0%, 50%, and 80% rela-
tive humidity.
Chitosan Coatings
Nanoclay (0.2, 1, and 2 wt%) was swelled in 30 ml of distilled water and dispersed
using ultrasonification tip (Branson Digital Sonifier) for 10 min. The dispersion was
added into 30 ml of 1% chitosan in 1% acetic acid, followed by sonication for 10
min. For reducing the surface tension and increasing the wettability, 60 ml of ethanol
was added and mixed under rigorous mixing. For coated multilayer structures, the
solutions were applied onto plasma-activated LDPE coated paper using the standard
coating bar no. 6 (wet film deposit of 60 µm). Chitosan solutions with initial nanoclay
concentrations of 0, 17, 50, and 67 wt%, and total coating dry weight of 0.2-0.6 g/m 2
were used.
Pectin Films
Aqueous solutions of pectin were prepared into distilled water by mixing pectin and
glycerol at final concentrations of 5 and 1.75 wt%, respectively. The pH of the mixture
was adjusted to pH 4.5 and the mixture was heated at 60°C for 2 hr to increase fluidity.
0.5, 1 or 2 wt% nanoclay was added to pectin solutions and immersed for 2 days un-
der constant mixing. Fluidizer (Microfluidics M110Y) was used for homogenization
of nanoclay/pectin dispersions. Feed solutions were pumped from inlet reservoir and
pressurized by an intensifier pump to high pressure (900-1350 bars) and fed through
fixed geometry chambers with inside micro channel diameter varying between 100
and 400 µm. Films of pectin and nanoclay were prepared by casting 15 ml of each
solution in polystyrene Petri dish (Ø 8.5 cm) and dried for 2 days at room temperature.
Final nanoclay concentrations in the solvent cast hybrid films were 10, 20, and 30
wt%.
disCussioN aNd results
Nanoclay was delivered as dry powder with particle size of 2-15 µm. Nanoclays typi-
cally tend to be agglomerated when mixed into water. The agglomerates are held