Analysis of the kinetics of agglomerate erosion in simple shear flows

A model for the erosion kinetics of particle agglomerates in simple shear flows has been developed. The erosion rate is taken to be proportional to the difference between hydrodynamic and cohesive forces and to the rotation velocity of the dispersing agglomerate. For dispersion under identical hydrodynamic conditions, the model predicts faster erosion for larger agglomerates. Moreover, at equivalent hydrodynamic stress, erosion is enhanced at higher shear rates. Dispersion experiments using silica agglomerates of various densities and liquid low molecular weight polymers (e.g., poly(dimethyl siloxane)) of different viscosities were conducted in an oscillatory shear flow device. The experimental results validate the erosion model; the general shape of the erosion kinetic curve, and the effect of viscosity, shear rate and agglomerate size on dispersion kinetics are well predicted. The model can also predict erosion for agglomerates with fractal structure.