105
oxide (ZnO) particles have an antimicrobial activity similar to that of other metal
oxides, and are preferred for its low cost and its UV-blocking properties.
6.3.3 Carbon-Based Nanomaterials
Graphene is the building unit of graphite. The exfoliated graphite nanoplatelet or
graphite nanoplatelet is a three-dimensional layered mineral allotrope and contains
a stack of more than 10 layers of carbon atoms (Gorrasi et al. 2018). A thinner version of graphene is known as graphene nanosheets and has different derivatives that
are presented as oxide, reduced oxide and nanoplatelets. Among them, graphene
oxide is rich in functional groups such as carboxyl, epoxide and hydroxyl, thus has
a high potential to be used in biobased nanocomposite materials. Nanoplatelets and
nanosheets of graphite have lower functional groups, and they are hydrophobic,
therefore do not contribute to polar interactions or hydrogen bonding.
In general, the exfoliation of graphite in layered graphene sheets is based on the
disruption of van der Waals-like forces between the graphite layers. The use of graphene within a composite improves the mechanical and barrier performance, as well
as electrical and thermal conductivity (Unalan et al. 2014).
Carbon nanotubes are formed by concentric tubes entitled as single-wall or
multi-wall nanotubes. These fillers show remarkably high aspect ratios and Young’s
modulus (E) with a high reinforcing capacity of biobased polymers (Zhou et al.
2004). These fillers are used not only for their performance to improve thermal/
mechanical/barrier properties of polymer composites, but also for their compatibility with chemicals, metal/metal oxide/chalcogenides NPs, and non-scattering electron transports (McEuen et al. 1999; Baur and Silverman 2007).
6.3.4 Polysaccharide Based Nanostructures
Cellulose-based nano-fillers are classified into three groups: cellulose microfibers,
nanocrystalline cellulose or cellulose nanowhiskers (Azizi Samir et al. 2005).
Cellulose nanofibers include a group of elongated molecules, which are stabilized
by hydrogen bonds. Cellulose nanowhiskers consist of the crystalline part of the
micro fibrils, which is obtained by acid hydrolysis (Gorrasi et al., 2018). The microfibrils are composed of crystalline and amorphous parts, which have nanosized
diameters and micrometer size lengths (Oksman et al. 2006). The lengths of
nanowhiskers, which are also recognized as nanocrystals, nanorods or rod-like cellulose microcrystals, range between 500 nm – 2 μm, 8–20 nm or less in diameter
providing high aspect ratios (de Souza Lima and Borsali 2004). The cellulose crystals had about 150 GPa of modulus and 10 GPa of strength, thus suggesting the
potential use of cellulose instead of carbon nanotubes (Helbert et al. 1996). The
moisture resistance of biobased polymers has also been improved by cellulose
6 Functional Biobased Composite Polymers for Food Packaging Applications
oxide (ZnO) particles have an antimicrobial activity similar to that of other metal
oxides, and are preferred for its low cost and its UV-blocking properties.
6.3.3 Carbon-Based Nanomaterials
Graphene is the building unit of graphite. The exfoliated graphite nanoplatelet or
graphite nanoplatelet is a three-dimensional layered mineral allotrope and contains
a stack of more than 10 layers of carbon atoms (Gorrasi et al. 2018). A thinner version of graphene is known as graphene nanosheets and has different derivatives that
are presented as oxide, reduced oxide and nanoplatelets. Among them, graphene
oxide is rich in functional groups such as carboxyl, epoxide and hydroxyl, thus has
a high potential to be used in biobased nanocomposite materials. Nanoplatelets and
nanosheets of graphite have lower functional groups, and they are hydrophobic,
therefore do not contribute to polar interactions or hydrogen bonding.
In general, the exfoliation of graphite in layered graphene sheets is based on the
disruption of van der Waals-like forces between the graphite layers. The use of graphene within a composite improves the mechanical and barrier performance, as well
as electrical and thermal conductivity (Unalan et al. 2014).
Carbon nanotubes are formed by concentric tubes entitled as single-wall or
multi-wall nanotubes. These fillers show remarkably high aspect ratios and Young’s
modulus (E) with a high reinforcing capacity of biobased polymers (Zhou et al.
2004). These fillers are used not only for their performance to improve thermal/
mechanical/barrier properties of polymer composites, but also for their compatibility with chemicals, metal/metal oxide/chalcogenides NPs, and non-scattering electron transports (McEuen et al. 1999; Baur and Silverman 2007).
6.3.4 Polysaccharide Based Nanostructures
Cellulose-based nano-fillers are classified into three groups: cellulose microfibers,
nanocrystalline cellulose or cellulose nanowhiskers (Azizi Samir et al. 2005).
Cellulose nanofibers include a group of elongated molecules, which are stabilized
by hydrogen bonds. Cellulose nanowhiskers consist of the crystalline part of the
micro fibrils, which is obtained by acid hydrolysis (Gorrasi et al., 2018). The microfibrils are composed of crystalline and amorphous parts, which have nanosized
diameters and micrometer size lengths (Oksman et al. 2006). The lengths of
nanowhiskers, which are also recognized as nanocrystals, nanorods or rod-like cellulose microcrystals, range between 500 nm – 2 μm, 8–20 nm or less in diameter
providing high aspect ratios (de Souza Lima and Borsali 2004). The cellulose crystals had about 150 GPa of modulus and 10 GPa of strength, thus suggesting the
potential use of cellulose instead of carbon nanotubes (Helbert et al. 1996). The
moisture resistance of biobased polymers has also been improved by cellulose
6 Functional Biobased Composite Polymers for Food Packaging Applications