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Deformation and orientation of single droplets during shear flow: combined effects of confinement and compatibilization

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Abstract

Combined effects of geometrical confinement and compatibilization on the deformation and orientation of single droplets during steady-state shear flow are investigated in a counter-rotating cell by means of microscopic observations. The model system consists of polydimethylsiloxane droplets of varying sizes and viscosities in a polyisobutylene matrix. To this system, a premade polyisobutylene–polydimethylsiloxane block copolymer is added as compatibilizer in different concentrations. For each droplet, the equilibrium interfacial tension is determined by comparing droplet axes with the predictions of the confined Minale model for uncompatibilized droplets at the appropriate degree of confinement. Although large reductions in interfacial tension are seen for all compatibilized droplets, it is shown that the effect of compatibilization on droplet deformation and orientation can efficiently be taken into account in the equilibrium capillary number. This way, for all viscosity ratios and confinement ratios, steady-state data for compatibilized and uncompatibilized droplets coincide, and agree well with the predictions of the confined Minale model at sub-critical conditions. For near-critical capillary numbers, compatibilization slightly reduces droplet deformation and postpones breakup, irrespective of the degree of confinement.

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Acknowledgements

The authors acknowledge the Research Foundation—Flanders (FWO Vlaanderen—post doctoral fellowship of A. Vananroye) and Onderzoeksfonds K.U.Leuven (GOA09/002) for financial support.

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Authors and Affiliations

  1. Department of Chemical Engineering, Katholieke Universiteit Leuven and Leuven Materials Research Centre, Willem de Croylaan 46, 3001, Leuven, Belgium

    Anja Vananroye, Peter Van Puyvelde & Paula Moldenaers

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  1. Anja Vananroye
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  2. Peter Van Puyvelde
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  3. Paula Moldenaers
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Correspondence to Paula Moldenaers.

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Vananroye, A., Van Puyvelde, P. & Moldenaers, P. Deformation and orientation of single droplets during shear flow: combined effects of confinement and compatibilization. Rheol Acta 50, 231–242 (2011). https://doi.org/10.1007/s00397-011-0535-4

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  • DOI: https://doi.org/10.1007/s00397-011-0535-4

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