Dilatancy, Jamming, and the Physics of Granulation

TL;DR

This paper explores how dilatancy and capillary forces influence the transition of colloidal suspensions into stable granules, combining theoretical models with preliminary experimental insights.

Contribution

It introduces a schematic model linking dilatancy and capillary forces to colloidal arrest and granulation, providing new understanding of the physics involved.

Findings

Capillary forces can stabilize solvent granules in a jammed state

Dilatancy physics converts into arrest physics during early granulation

Preliminary experiments show aspects of granulation in colloidal suspensions

Abstract

Granulation is a process whereby a dense colloidal suspension is converted into pasty granules (surrounded by air) by application of shear. Central to the stability of the granules is the capillary force arising from the interfacial tension between solvent and air. This force appears capable of maintaining a solvent granule in a jammed solid state, under conditions where the same amount of solvent and colloid could also exist as a flowable droplet. We argue that in the early stages of granulation the physics of dilatancy, which requires that a powder expand on shearing, is converted by capillary forces into the physics of arrest. Using a schematic model of colloidal arrest under stress, we speculate upon various jamming and granulation scenarios. Some preliminary experimental results on aspects of granulation in hard-sphere colloidal suspensions are also reported.