Paper
Depletion flocculation characterised by multisample analytical centrifugation
T. Sobisch, T. Detloff, D. Lerche
A considerable part of dispersions used in various technical applications show depletion flocculation. Under these circumstances the particle size distribution depends on polymer and particle concentration. Therefore, dilution has to be avoided if the particle size distribution has to be determined. Further, for technical separation processes like centrifugation the effective (apparent) viscosity of the polymer solutions is of interest. As polymer solutions often exhibit shear thinning behaviour the shear dependent apparent viscosity has also to be known for the determination of particle size distribution by analytical centrifugation. The paper describes a new method how one can determine the shear dependent apparent viscosity of polymer solutions in the centrifugal field in-situ using monodispersed particles as tracer. Based on this approach it is then possible to determine the overall particle size distribution of depletion flocculated dispersions and the particle size distribution of particles remaining in suspensions for given times of centrifugation. The approach was successfully applied to the characterization of polydisperse quartz dispersions.
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