Depletion flocculation characterised by multisample analytical centrifugation
T. Sobisch, T. Detloff, D. Lerche¹; Particulate Systems Analysis 2008, Stratford-upon-Avon, UK.
Abstract: In many industrial applications the properties of dispersions are adjusted by polymeric additives. Nonadsorbing polymers used as thickeners to stabilise formulations not only increase fluid viscosity but can also induce depletion flocculation. Both viscosity increase and depletion flocculation will modify separation stability. Particle size distributions in dispersions exhibiting depletion flocculation depend on polymer and particle concentration as well. Therefore related investigations have to be carried out in undiluted systems. In this paper we study the shear dependent sedimentation in a centrifugal field for monodisperse (silica) and polydisperse (quartz) dispersions in anionic polymer solution of varying concentration. A multisample analytical centrifugation technique with photometric detection (STEP-Technology) is used in this study to trace the sedimentation velocity as well as velocity and size distributions in-situ. Measurements with monodisperse silica were used to determine the effective viscosity as function of polymer concentration and centrifugal acceleration. In addition the sedimentation velocity of the coarse fraction and the particle size distribution in the supernatant was determined for the polydisperse quartz dispersions.
Key words: Colloidal stability • Depletion flocculation • Sedimenation • Polymer • Thickener • Silica • Particle size distribution • LUMiSizer
¹ L.U.M. GmbH, Dispersion Stability & Particle Analysis, Rudower Chaussee 29, 12489 Berlin, Germany.Contact us
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