It shows that the blend NR80CS20 exhibits the lower value; while
the chitosan exhibits the maximum value of dielectric constant. The
dielectric constant values of the blends decreased with increase in
frequency. The effect of blend composition on the dielectric constant
values is given in Table 2 for different frequencies. The table shows
that the dielectric constant of natural rubber is less at higher
frequencies. The blend NR85CS15 shows the least frequency dependent
and more stable. Above 20% chitosan in the blend, the dielectric
constant increased, which can be attributed to the change in overall
polarity of the system with the addition of chitosan.
Table 3 shows that the dielectric constant of blend after
vulcanization is more stable. The added dicumyl peroxide undergoes
cross-linking reaction in the rubber phase and the cross-links formed
at the interface decreases the free volume. The cross-linked structure
will avoid increase in free volume resulting in stable dielectric
properties. The effect of vulcanization on the dielectric constant for
the blend with 10% of chitosan is shown in Fig. 6. The dielectric
constant decreases by vulcanization and it is more stable than pure
blend at lower frequencies. The vulcanized NR90CS10 blend is more
stable than MA compatibilized NR90CS10 and the compositions
is given in Table 4
The blend NR85CS15 shows the least frequency
dependent and more stable. Above 20% chitosan in the blend, the
dielectric constant increased, which can be attributed to the change
in overall polarity of the system with the addition of chitosan. The
cross-linked structure will avoid increase in free volume resulting in
stable dielectric properties. The dielectric constant decreases by
vulcanization and it is more stable than pure blend at lower
frequencies. The vulcanized NR90CS10 blend is more stable than MA
compatibilized NR90CS10 and the vulcanized blend is frequency
independent at lower frequencies. The dielectric loss increases with
chitosan content. The magnitude of dielectric loss is minimum for
natural rubber and maximum for chitosan. As the chitosan content
increases, more dipoles are incorporated into the system that leads
to a lag in the orientation of the dipoles upon the application of
electric field. The dielectric loss decreases by the vulcanization and
compatibilization of the blend. The AC conductivity study shows the
vulcanized material sample becomes more insulative compared to
pure and MA treated blends
Dielectric constants at various frequencies for different blend compositions