Bio-hybrid Nanocomposite Roll-to-roll Coatings for Fiber-based Materials and Plastics - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 198

Chapter 18
Bio-hybrid Nanocomposite roll-to-roll Coatings for
Fiber-based materials and Plastics
Jari Vartiainen, Vesa Kunnari, and Annaleena Kokko
iNtroduCtioN
Development of innovative products starts from the raw materials. Packaging industry
relies heavily on oil-based materials in certain applications. Replacing the oil-based
material with bio-based products might give a competitive advantage due to more sus-
tainable and greener image. In addition, nanotechnology in food packaging is expected
to grow strongly over the next 5 years as the increased globalization sets demands for
shelf life enhancing packaging. Recently, a lot of effort has been aimed at developing
new bio-based polymer containing films and nanocomposites which can act as for ex-
ample barriers in packaging materials (Arora and Padua, 2010; Lagarón and Fendler,
2009; Vartiainen et al., 2010a, 2010b). Unlike synthetic plastics, in dry conditions, the
films and coatings from natural polymers exhibit good barrier properties against oxy-
gen and grease due to the high amount of hydrogen bonds in their structure. However,
natural polymers are hydrophilic in nature, thus films and coatings produced from
these materials are often hygroscopic, resulting in partial loss of their barrier proper-
ties at high humidity (Hansen and Plackett, 2008). A major challenge for the packaging
developers is to overcome the inherent hydrophilic behavior of biomaterials. Among
the potential fillers for nanocomposites, clay platelets have attracted a particular inter-
est due to their high performance at low filler loadings, rich intercalation chemistry,
high surface area, high strength and stiffness, high aspect ratio of individual platelets,
abundance in nature, and low cost (Blumstein, 1965). Clays are naturally occurring
materials composed primarily of fine-grained minerals. Nanoclays (or nanolayered
silicates) such as hectorite, saponite, and montmorillonite are promising materials
with high aspect ratio and surface area (Lan et al., 1994; Messersmith and Giannelis,
1995; Yano et al., 1997). Because of their unique platelet-like structure nanoclays
have been widely studied regarding the barrier properties. Such nanoclays can be very
effective at increasing the tortuosity of the diffusion path of the diffusing molecules,
thus significant improvement in barrier properties can be achieved with the addition
of relatively small amounts of clays (Pavlidou and Papaspyrides, 2008). When the
nanoclay layers are completely and uniformly dispersed in a continuous polymer ma-
trix, an exfoliated or delaminated structure is obtained. Full exfoliation (single platelet
dispersion) of nanoclay by using existing/traditional compounding techniques is very
difficult due to the large lateral dimensions of the layers, high intrinsic viscosity of the
polymer and a strong tendency of clay platelets to agglomerate (Hussain et al., 2006).
Most of the clays are hydrophilic, thus mixing in water with water-soluble polymers