Page 672 - Polymer-based Nanocomposites for Energy and Environmental Applications

618 Polymer-based Nanocomposites for Energy and Environmental Applications

can be overcome by the use of polymer composites from renewable sources. These are
the alternatives for the sustainable development of economically and ecologically
green technologies [4]. The green polymer nanocomposites are expected to improve
the speed of manufacturing, recycling, and compatibility [5]. The most interesting
features of green polymer nanocomposites are eco-friendly, biodegradable, and
sustainable. The basic necessity of green polymer nanocomposites is that the polymer
should be green (renewable and biodegradable). The classification of biodegradable
polymers is given in Table 23.1. The polymeric materials are divided into two major
groups such as agricultural polymers and biopolyesters. These were further classified
on the basis of their origin and the path of their production.

23.2 Processing methods for polymer nanocomposites

The processing methods for polymer nanocomposites are categorized into four major
routes such as melt intercalation, template synthesis, exfoliation adsorption, and
in situ polymerization intercalation [6-11]. The three different kinds of structures
(exfoliated (Fig. 23.1), intercalated (Fig. 23.2), and unintercalated or aggregated
(Fig. 23.3)) can be obtained on the basis of method and materials used.

23.2.1 Melt intercalation
This method involved the annealing of polymer matrix at the higher temperature
and then addition of filler and finally kneading the composite to obtain uniform
distributions. This method is a standard approach for the production of thermoplas-
tic polymer nanocomposites. It is considered as eco-friendly because no solvent is
used in the process and is compatible with industrial processes like injection mold-
ing and extrusion. The processing conditions like surface modification of fillers,
compatibility of filler, and polymer matrix played an important role in determining
the quality of dispersion achieved. The relationship between the processing condi-
tions and morphologies was well discussed by Alig et al. [12].Inthe same way,
Pavlidou and Papaspyrides [9] discussed the thermodynamics and effects of
multiple conditions. The only disadvantage of this process is the use of higher
temperature that can damage the surface modification of fillers. Therefore, the
optimization of conditions is very important in order to achieve good dispersion
and exfoliation. For example, operating at lower temperature or at thermally stable
conditions can avoid degradation [7].

23.2.2 Exfoliation adsorption
This method is based on the solvent in which polymer or prepolymer is solubilized and
is also known as polymer or prepolymer intercalation from solution. This method
is widely used for the synthesis of intercalated nanocomposites from water-soluble
polymers with low or no porosity. In this method, the layered silicate is first swollen
and dispersed in the solvent before mixing it with the polymer. After that, the polymer