Page 350 - Polymer-based Nanocomposites for Energy and Environmental Applications

Modification of polymer nanocomposites and significance of ionic liquid 317

H H H H H
CC
H H H H HH n
Ethylene
Polyethylene
Fig. 11.1 Polyethylene is an example of polymer composed of n-ethylene monomers.

Among monomers, the chemical reaction that leads to the formation of polymer is
called polymerization [12]. To describe polymerization, polyethylene is used as an
example.

11.2.3 Physical, thermal, mechanical properties

The solubility, flexibility, stiffness, and strength of polymers depend on their mechan-
ical, thermal, and physical properties. Therefore, the quantification of these sub-
stances is important for engineering applications. In practice, the molecular weight
of a polymer needs to be determined. Monomers have low molecular weight, but
throughout the polymerization procedure, the molecular weight of the resulting mono-
mer chains increases. However, it is difficult to measure the exact molecular weight of
a specific polymer because the participating chemical units at the branching and end
points behave in a different way compared with the ones in the main molecular chains.
Furthermore, the molecular structure of polymers affects their mechanical properties.
In particular, it has been reported that the entanglement and branching of molecular
chains enhance the strength and rigidity of polymers [13]. In addition, crystals in poly-
mer structure result in the improvement of their mechanical properties. The mechan-
ical properties of polymers are based also on its temperature. In particular, each
polymer is characterized by a specific temperature called “glass transition
temperature.” In fact, the polymers’ stiffness and strength below glass transition
temperature decrease slowly with increasing temperature, and the overall material
behavior is brittle.

11.3 Environmental aspects of polymer nanocomposite

Polymer composites from renewable reserves grabbed tremendous focus from past
20 years owing to ecological concerns and swiftly depleting conventional power
sources [14]. The utilization of polymer composites from renewable resources has
preference above artificial sources, mainly as a resolution to the environmental harms
developed by plastic waste [15]. The rapid increase in environmental pollution claims
for novel eco-friendly polymers particularly for food packaging applications. Bio-
composites are latest light mass eco-friendly structure materials where both the poly-
mer matrix and the reinforcement create from biomass. The plant-based resins and the
natural fibers have displayed to associate the low-cost composite with good