Page 351 - Polymer-based Nanocomposites for Energy and Environmental Applications

318 Polymer-based Nanocomposites for Energy and Environmental Applications

mechanical properties. The use of natural fibers received global attention after
replacing synthetic fibers. In composite applications, the hard fiber equality is the
most common. Furthermore, as they are derived from renewable sources, they can
characterize environmentally friendly alternatives to conservative reinforcing fibers
(carbon and glass Kevlar) [16]. In the future, it might be possible for manufacturers
to use green nanotechnology for ecological composite production and the ability to
control the use of perilous explosive organic compounds and solvents, namely, meth-
ylene chloride and toluene, which presents a menace to human health and biodiversity.

11.4 Graphene

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Graphene is an atomically thick, two spatial sheets composed of sp carbon atoms set
in a honeycomb crystal lattice [17]. It is the basic structural unit for carbon allotropes
such as fullerenes, carbon nanotubes, and graphite. It was first recovered by mechan-
ical cleavage of graphite with Scotch tape [18]. Graphene is one of the thinnest well-
known materials presented to us and is the mother of graphitic carbon materials [19].
Graphene is barely soluble in common solvents and has a strong affinity to agglom-
erate irrevocably or even to restack into graphite-like structures. Graphene is an out-
standing substance for supercapacitor electrode due to its very high thermal
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conductivity, high surface area (2675 m /g), very high mechanical strength, and
extreme electric conductivity. Graphene radically advances the properties of
polymer-based composites at extremely low loading, and its most interesting property
is the very high surface conductivity leading to the development of various electrically
conductive polymer composites. Such conducting graphene nanocomposites have
been broadly useful in electromagnetic interference shielding, chemical sensor bipolar
plates for fuel cells, antistatic materials, etc. Another probable application comprises
electrostatic dissipation and radio-frequency interference shielding for electronic
devices [20–22].
It also exhibits some unique chemical, mechanical, electric, and thermal properties.
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Its chemical properties are generally, because of its sp -bonded hybridization and the
extreme materialization of the surface (two faces with no bulk left in between) [23].
Graphene also exhibits remarkable stiffness among materials found in this world.
After using it as fillers with the insulating polymer matrix, conductive graphene could
really increase the electric conductivity of the composites. At certain loading fraction,
identified as percolation threshold, the fillers are capable of forming a network leading
to a rapid increase in the electric conductivity of the composite [24]. Advanced ther-
mal transport properties of graphene dispersions have prospective for the thermal
executive in thermal pastes [25] for heat-actuated shape-memory polymers and for
miniaturized electronic devices [26]. It has been reported that 2-D, platelet-like
GNP can develop thermal conductivity additionally effective than 1-D rodlike carbon
nanofillers or carbon nanotubes [27]. Thermal stability is one more imperative prop-
erty that can be superior by embedding graphene in polymer matrices.