Generalized model for the aggregation rate of colloidal nanoparticles and clusters induced by shear in the presence of repulsive interactions

Aggregation of colloidal nanoparticles in the presence of shear is a key step in processing of many particulate materials, polymeric nanoparticles, food products etc. Predicting the rate of aggregation is importance in order to optimize the operating conditions under which coagulation takes place. In this work, we have performed detailed simulations of the aggregation rate of colloidal nanoparticles in the presence of both linear shear flow and repulsive interactions, by numerical solution of the convection-diffusion equation for the pair probability function, from which aggregation rates are computed. Using a simplified model we have interpreted the results of the rigorous calculation and provided a simple criterion to determine the relative importance of all mechanisms involved in the aggregation. The main result is that sufficiently high shear rates can cancel the effect of repulsive interactions and lead to the same aggregation rates found in fully destabilized suspensions.