Rj. Zeng et B. Rand, Effects of Dispex A40 on rheology and filter pressing behaviours of concentrated alumina suspensions, J MAT SCI T, 17(6), 2001, pp. 664-666
Variation of plastic viscosity and extrapolated shear yield stress with the
concentration of Dispex A40 for the concentrated Alcoa A16 alpha -Al2O3 su
spensions at 0.27 powder volume fraction was investigated at 294 K. An opti
mum level of Dispex A40 for full deflocculation is found to be at 0.18% mas
s fraction of the powder, at which the rheological behaviour shows little d
ifferent to that of adjusting the pH to 4 to obtain full deflocculation. It
is demonstrated that the shear stress drop can roughly work as an index fo
r the thixotropy in particular fixed conditions, and consequently an index
for the deflocculation as the shear stress drop becomes larger when the lev
el of the flocculation increases, and vice versa. It is also found that the
addition of Dispex A40 can prevent the filter cakes from cracking, whereas
the cakes at various pH values with polyvinyl alcohol as a sole polymer no
rmally develop cracking during drying.