Abstract
The correlation between rheological behavior of a slurry, composed of silica microspheres and poly (vinylalcohol) (PVA), and microstructure and also the disintegration behavior of spray-dried granules were studied. Pseudoplastic flow behavior was analyzed under the Bingham approximation to obtain the Bingham yield value, τB, plastic viscosity, ηpl, and bulkiness of the flow unit, CFP. CFP is the ratio of the effective volume fraction of flocs, φF, to that of dry solid, φP. The dispersion of silica in the slurries was dominated by PVA adsorption at low pH and the electrostatic repulsion at high pH. The granules prepared from the slurry at pH=7 had the smallest apparent density and disintegrated under the smallest applied load. It is concluded that the microstructure and disintegration behavior of the granules are greatly affected by pH values at which the slurries are prepared, in spite of the similar flow behavior.
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