Crystallization and Melting Behavior (DSC):
The pres-
ence of RHF showed significant effects on the cooling behavior
of the composites. The DSC thermograms obtained during
cooling are shown in Figure 4. Only one exothermic peak
was registered for all the samples. For PP processed without
RHF the crystallization peak was observed at
T
c
=113
o
C
while for the composites these exothermic peaks shifted to
higher temperatures in all cases. The determined
T
c
values
are shown in Table I. The higher
T
c
values of the composites
indicate that the crystallization is favored in the presence of
the rice husk particles. The
T
c
increase can be considered to
be due to the nucleation effect of the rice husk: fibers act as
sites for heterogeneous nucleation thus inducing the crystal-
lization of the matrix.
1,16
Figure 5 shows the heating thermograms of selected sam-
ples obtained from the second heating range. For both neat
PP and PP/RHF composites only one single endothermic
peak was observed at similar temperatures (near 164
o
C),
corresponding to the melting of the
α
-crystalline phase of
the PP sequences. These results indicate that the presence of