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Rheology of sticky grains
In many powder technology processes, coating is applied to fine particles to control their properties or functionalize them. We investigated the role of a polymer coating made of PBS on silica beads. This material has been originally designed as a model cohesive granular material, whose cohesion can be finely controlled by the thickness of the coating (A. Gans et al 2020). However, we show that the coating not only introduces adhesion but also modifies the friction between the grains. Due to the viscoelastic properties the coating, the inter-particle friction coefficient depends on the load and the velocity. By means of numerical DEM simulations, we demonstrate that this transition in the inter-particle friction coefficient can induces complex behavior for the bulk rheology such as shear-thickening and shear-banding.