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Influence of droplet size on the rheological behavior of emulsions

: Teipel, U.


Chemical Engineering and Technology 25 (2002), No.6, pp.609-615
ISSN: 0930-7516
ISSN: 1521-4125
Journal Article
Fraunhofer ICT ()

This study examined emulsions with two different mean droplet diameters under steady and oscillatory shear flow. Because the emulsions had a very low dispersity xi < 0,41 (meaning that they were nearly unimodal), the influence of droplet size alone on the rheological behavior could be determined. For emulsions with equivalent concentrations tested at equivalent shear rates, the emulsion containing droplets with (x) over bar = 1 mum exhibited higher shear stress values than the emulsion with droplet diameters (x) over bar = 20 mum. Up to a concentration c(v) = 40 vol.-%, the difference in the shear stress function was observed over the entire shear rate range. The difference in the shear stress functions was largest at low shear rates. The oscillatory experiments yielded results consistent with the steady shear experiments, i.e., the complex shear modulus of the "1-mum-emulsions" was greater than that of the "20-mum-emulsion" at a constant oscillatory frequency. A nearly constant increase in the complex shear modulus with frequency was observed over a wide range of concentration; as a result the difference in the moduli was nearly constant over the frequency range examined.