472046 A Population Balance Based Model to Describe the Rheology of Thixotropic Suspensions with a Yield Stress
Starting from the population balance equation for colloidal dispersions, a monodisperse closure rule is used to develop a coarse grained structure evolution equation. Moving beyond previous efforts, important modifications are made to account for dynamic arrest of aggregation kinetics at the onset of the yield stress and to enforce a minimum particle size below which breakage is not feasible. The resulting population balance model is coupled to a simple constitutive equation to complete the model allowing us to predict the effects of aggregation and breakage processes on the rheology. The overall model provides a reasonable representation of experimental data for a model thixotropic suspension available in the literature . The resulting model is able to capture the dominant thixotropic timescales for unidirectional shear flows in step-up and step-down transient experiments. In addition, predictions of rheology under large amplitude oscillatory shear (LAOS) and flow reversal experiments are also compared to experimental measurements. The coarse grained model equations are also compared to prevalent structure kinetics models and shown to be distinct, emphasizing the novelty of using a population based model as a basis for thixotropic suspension modeling.
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