Modulus of the rubber/PH blends
Figure 10 shows the modulus of the blends as a
function of volume fraction of PH obtained by the
experimental measurements and estimated values
using Halpin-Tsai equation. It is observed that the
variation of the modulus with resin content for both
rubbers can be well described by Halpin-Tsai equation
at low resin content. After a certain value of
resin content, 15 vol %, moduli indicate a deviation
from eq. (5) and the results show a sharp
increase, particularly at higher resin content. This
observation suggests much more contribution of the
PH upon the modulus of the blends at higher volume
fraction. There could be some possibilities for
this behavior. One possibility could be the alteration
of the phase morphology of the blend and converting
to cocontinuous morphology. Because, in such
cases, the PH can play considerable role on the
modulus of the blends.34,35 However, this explanation
is somewhat questionable, because the volume
fraction of 0.15 seems to be too low for the rubber/
PH blend to become cocontinuous. Only partial
cocontinuity due to the tendency of the PH-dispersed
phase for agglomeration may be a reasonable
explanation for the mechanical behavior of the
blend mentioned earlier.