Page 680 - Polymer-based Nanocomposites for Energy and Environmental Applications

Green polymer nanocomposites and their environmental applications 625

23.3.6 Protein-based nanocomposites

The soy protein is available widely and is least expensive as compared with other com-
mercially available materials. It has been reported that the protein-based resins
exhibited good adhesion with the plant-based fibers and produced composites with
excellent mechanical properties as compared with the other hydrophobic biodegrada-
ble resins [58,59]. This is because of the presence of polar groups in the protein-based
resins. Commercially, soy protein is available in different varieties such as soy protein
isolate (SPI) ( 90%), soy protein concentrate (SPC) ( 70%), and soy flour ( 50%).
Soy proteins are ductile and can undergo physical changes without any damage such
as bending, torsional, and tensile deformations [60]. Soy proteins are able to form new
materials with significantly improved mechanical and thermal properties after certain
modifications [58,59,61-67]. Soy proteins can be modified by using various materials;
for example, modification of SPI by stearic acid can enhance the moisture absorption
resistance [58], and modification with glutaraldehyde and polyvinyl alcohol followed
by fabrication of composites with flax yarns and fabrics can exhibit improved proper-
ties [64,65]. Otaigbe and Adams [68] used phosphate fillers for soy protein composites
and achieved improved mechanical properties and water resistance. Rhim et al. [69]
demonstrated that there was an increase in the tensile strength with enhanced water
vapor permeability when SPI films were modified by bentonite or chitosan/MMT.
An animal protein gelatin was used for the synthesis of biocomposites with MMT clay
and has exhibited improved mechanical and water resistance.

23.3.7 Lipid-based nanocomposites

Lipids are mainly used for the formation of edible films. The most commonly used
lipid materials for the coating of food or drug surface are beeswax, carnauba wax,
candelilla wax, triglycerides, fatty acids etc. These materials can provide moisture
properties to the composite films. The composite films are composed of both lipid
and hydrocolloid (proteins or polysaccharides). The advantages of such kind of films
are as follows: When a water vapor barrier property is required, the lipid component
can function, and when mechanical strength is required, then hydrocolloid component
will do necessary function.

23.4 Applications of green polymer nanocomposites

Polymer nanocomposites introduces a new era of the polymer industry toward the sus-
tainable environment. In other words, polymer nanocomposites from renewable
sources have received an enormous attention from last two decades because of the
environmental concerns and depleting energy sources [70]. On the other hand, green
nanocomposites have overtaken the traditional composites in production, develop-
ment, and usage applications. Green nanocomposites are widely used in a variety
of applications in the development of products such as automotive parts, building
block based on cellulose nanofibers, blades for vacuum cleaners, power tool housing