Rheology and Surface Properties of Filled Dispersions

Rheology and wetting properties of commercial water-born dispersion of the copolymer of vinyl ester of a synthetic saturated monocarboxylic acid and acrylate, obtained by emulsion polymerization, have been investigated. For composition modification, 0.8 phr of dibutylglycol as plasticizer and from 0 to 10 phr of TiO2 and Al2O3 particles as filler were added. It has been shown that dispersion behaviour under shear between two coaxially placed cylinders depends not only on the dispersion composition, but on the shear rate as well. At low shear rates (up to 40 s-1), an increase of the viscosity was found, while at higher shear rates dispersion shows pseudoplastic behaviour. Effective amount of TiO2 decreases the intensity of determined anomalies. For pure, plasticized and TiO2 modified dispersions, a tendency to restore viscosity value by decreasing the shear rate was found. This effect for Al2O3 filled dispersion was insignificant. The results of advancing contact angle measurements showed that an addition of up to 3 phr of mineral filler to the dispersion does not change its wetting properties. Higher amounts of fillers worsen wettability properties.