Jamming and the onset of granulation in a model particle system

Abstract: Granulation is a ubiquitous process crucial for many products ranging from food and care products to pharmaceuticals. Granulation is the process in which a powder is mixed with a small amount of liquid (binder) to form solid agglomerates surrounded by air. By contrast, at low solid volume fractions {\phi}, the mixing of solid and liquid produces suspensions. At intermediate {\phi}, either granules or dense suspensions are produced, depending on the applied stress. We address the question of how and when high shear mixing can lead to the formation of jammed, non-flowing granules as {\phi} is varied. In particular, we measure the shear rheology of a model system - a suspension of glass beads with an average diameter of $\sim$ 7 {\mu}m - at solid volume fractions {\phi} $\gtrsim$ 0.40. We show that recent insights into the role of inter-particle friction in suspension rheology allow us to use flow data to predict some of the boundaries between different types of granulation as {\phi} increases from $\sim$ 0.4 towards and beyond the maximum packing point of random close packing.