Chemistry Reference
In-Depth Information
medium viscosity
m
is universally dependent on irrespective of the particle radius
[48, 52]. The
eff
of four CB aggregates (
eff
) was evaluated by comparing the
/
m
ratios of the CB aggregates and the universal
/
m
versus curve for the
hard-core silica particles. The results are shown in Figure 16. From the abscissa
coordinates of the plot for the CB aggregates (open symbols), the value was
estimated to be 2.6, 2.6, 5.5, and 16 for the CB-76, CB-24-1, CB-15-2, and AcB
suspensions, respectively. This result indicates that the value or the effective
volume is an important parameter to characterize CB aggregates. With increasing
shear rate, the density of the three-dimensional network of the CB aggregates is
decreased. Under sufficient high shear, the size of flow unit becomes the CB
aggregate size. In this shear region, the second Newtonian flow appears. Therefore,
the CB aggregates are considered to be a flow unit corresponding to “effective
volume”. The value increases with increasing the DBP absorption value,
suggesting that
eff
depends mainly on aggregate structure morphology irrespective
of particle size. This result indicates that the CB aggregates behave as a flow unit at
high shear rates and the difference between
eff
and reflects mainly the non-
spherical shapes of the aggregates.
Figure 16. Relative viscosity
r
versus effective volume fraction
eff
plots of the
CB-76/(PS/DBP), CB-24-1/(PS/DBP), CB15-2/(PS/DBP), and AcB/(PS/DBP)
suspensions. The
eff
values were determined in a way that the
/
m
versus
eff
for four
suspensions were superposed on the universal
/
m
versus plots obtained for unimodal
hard-core particles [32].
