Page 36 - Polymer-based Nanocomposites for Energy and Environmental Applications

Introduction of polymer-based nanocomposites 15

will create defects that lead to a deleterious effect on the mechanical properties of the
PNCs [111].
In this field, Rapacz-Kmita et al. [112] represented the influences of the
organophilization process on the properties of organobentonite fillers to improve
the mechanical factors of clay/PNCs. Also, in another research [113], hydropho-
bic kraft fibers were achieved by organo-nanoclay modification. The treated
fibers were used as reinforcement for improving mechanical performance and
dimensional stability of high-density polyethylene (HDPE) composites. Also,
Maitra et al. [114] discussed the possible micromechanisms that were responsible
for the enhancement of the mechanical properties of ND-reinforced polymer-
matrix composites.
In addition, residual stress is one of the crucial factors that can affect on the deg-
radation of PNCs. Upadhyaya et al. [115] investigated the effect of nanoclay com-
pounding on the thermooxidative degradation and the residual stresses due to
thermal oxidation for a thermoset polymer via a three-dimensional (3-D)
micromechanics-based finite element analysis (FEA).

1.6.2 Thermal properties
Dimensional stability of neat polymers in high temperature due to their high ther-
mal expansion coefficient has been resolved by using the nanoparticles. This appli-
cation is regarding to the enhancement of thermal stability for PNCs [111].For
example, the effects of the dispersion and concentration of single-walled carbon
nanotube (SWNT) on the flammability of polymer/SWNT nanocomposites were
investigated. In this research, the flammability factors were analyzed by
employing a cone calorimeter in air and a gasification device in a nitrogen
atmosphere [116].
Similar to the mechanical properties, the thermal characteristics of PNCs
such as dimensional stability and flammability can be affected by dispersion
degree of nanoparticles. In case of poor dispersion and low interaction surface
between the polymer matrices and nanoparticles, it may cause some defects that
decline thermal properties of PNCs. For example, these defects can be illustrated
as crack or openings among the thermal tests and cannot retain materials from
dimensional change.

1.6.3 Electrical and optical properties

Generally, polymer materials have low electric conductivity. In case of using these
polymeric products for electric devices, they require to be enhanced among their elec-
tric characteristics. Combination of polymer matrices with conductive nanoparticles
can make conductive PNCs that are applicable in electronic devices. These products
not only represent the electric conductivity but also have specific properties relating to
the polymeric components such as flexibility and low cost of production.