A shear cell to characterise internal friction in high-pressure compacted powder beds

Abstract Many processes submit bulk particulate materials to high pressure, for example, polymeric powders can be subjected to pressures of the order of 100 MPa in an extruder. However, methods to characterise the shear properties of powders at these high pressures have not been available. This paper describes a novel shear cell designed to measure the internal friction properties of powders at up to 100 MPa. The cell is designed to induce movement of an annulus of the compacted powder in contact with the stationary central cylindrical core and the resulting shear stress is recorded. A key feature is that no bearings are involved in the shearing process. Coefficient of friction data measured at high pressure on a family of polymer powders show correlation with extrusion output, confirming the potential value of this high pressure shear cell in developing understanding of this and other processes involving powders at high pressure.