Page 196 - Polymer-based Nanocomposites for Energy and Environmental Applications

168 Polymer-based Nanocomposites for Energy and Environmental Applications

declines with increase in loading, and this is again a concern. Better insight of inter-
facial interaction needs modeling and simulation that presents a real picture of the
electric field effect on the breakdown strength. Use of nanofibers in place of
nanoparticles offers various merits as the nanofibers are less prone to aggregation
due to comparatively lower surface energy. The flexibility of the nanocomposites thus
enhances at lower filler loading as the percolation is obtained very easily due to the
higher aspect ratio of the fillers. However, at the percolation threshold, even a slight
change in loading produces a significant variation in the electric properties. Therefore,
utmost care is needed at the percolation threshold. The fillers that generally decrease
the remnant polarization of the nanocomposites are best to achieve higher energy den-
sity. An ideal nanocomposite should have dielectric properties that are relatively less
sensitive to frequency and temperature. So, for high-temperature operations, a thermal
management system is needed [281]. Therefore, more work is needed in this sense to
have stable electric properties. The effects of the size of fillers on the dielectric prop-
erties have been studied extensively. Out of various fillers addition methods in the
polymer matrix as suggested by Newnham, only 0–3 and 1–3 type of nanocomposites
are enormously used, due to the easy handling. Enormous efforts are needed to reveal
the dielectric properties of other combinations of nanocomposites as well. In recent
times, dielectric nanocomposites are being exploited to design wearable sensors that
require a film of very small thickness. Fabricating flexible thinner films with opti-
mized properties is itself a daunting task.

5.8 Conclusion

The basic requirement of the nanocomposites material for electric properties is that it
should be of low cost, lightweight, nontoxic, and flexible in nature. Most of the efforts
carried out all around the world has been focused on optimizing all the dielectric
parameters imperative for efficient use as high-energy-density materials. The dielec-
tric properties are based on various factors including type, size, concentration, and
physical and chemical properties of the fillers as well as on the nature of the polymers.
As the dielectric properties of the polymer nanocomposites are influenced by the
dielectric properties of both fillers and the polymers, the choice of a proper polymer
becomes crucial in setting the final dielectric properties. So, the dielectric properties
can be optimized according to the requirement. The most important parameters to pre-
pare flexible polymer nanocomposites are fillers with large dielectric constant and
their percolation thresholds. Care has to be taken while working with high-dielectric-
constant fillers, as it may lead to inhomogeneous distribution of electric field can be
responsible for dielectric breakdown. To obtain uniform dispersion and enhanced
dielectric properties, surface modification of fillers is a must. Conducting nanofibers
are the feasible candidates for obtaining flexible nanocomposites, for these exhibit
higher dielectric constant and lower dielectric loss with a much lower percolation
threshold in comparison with the ceramic-based fillers. More recently, ternary
nanocomposites containing nanoparticles and nanofibers as fillers in a single polymer
or fillers with polymer blends are being explored because of their enhanced properties