Influence of Polyelectrolyte Addition on Rheological Properties

GARRIDO, L. B.; A.N. CALIFANO

Viscoelasticity: theories, types and models

Nova Science Publishers, Inc

Año: 2011; p. 1 - 16

The preparation of porous ZrO2 had received much attention last years due to its extensive industrial applications (ceramic filters, catalyst supports, solid oxide fuel cells, membranes for gas filtration, biomedical materials, etc.). To produce porous ceramics starch is incorporated in the ceramic formulation acting as pore former and binder agent. The porous structure is highly dependent on the properties of the starting materials and suspension conditions, such as ZrO2 particle and starch granule sizes, volume ratio of the ceramic/starch and stability. The powder mixture must be dispersed in water to achieve optimum particle packing through colloidal processing. This requires the preparation and dispersion of highly concentrated suspensions which are fundamental steps in the colloidal processing of ceramics. Appropriate processing requires low viscosity and high solid content as possible. Thus rheological properties of concentrated aqueous suspensions of zirconia (3Y-ZrO2) containing different relative amounts and types of starch granules has been studied. Corn and potato starch types were incorporated in the starting powder composition as these starch varieties exhibit significant differences in their chemical and morphological characteristics. Shear viscosity and linear viscoelastic measurements using oscillatory techniques were performed on the highly concentrated (50 and 58.6 vol%) aqueous suspensions. The effect of the variable amount of an anionic polyelectrolyte added as dispersant, on rheological properties of the zirconia suspensions with and without starch was examined, providing information about differences in suspension structure due to modifications of the interparticle interactions. In the absence of starch, well stabilized zirconia suspension was obtained by 0.12 wt% of polyelectrolyte at pH 9 and began to flocculate at higher additions. Rheological measurements showed that a higher amount of the anionic polyelectrolyte was suitable to stabilize the mixed suspensions containing 45 and 68.7 vol% of corn starch in the composition. Rheological properties of zirconia suspensions containing potato starch resulted less dependent on polyelectrolyte addition.