(149a) Mechanical Testing on Small Quantity of Loosely Compacted Cohesive Powders

The study of bulk behaviour of cohesive powders is very important in the processing of particulate solids such as flow out of storage vessels, filling and dosing of small quantities of powder in capsules and dispersion in dry powder inhalers. Although the mechanical properties of bulk cohesive powders have been analysed extensively at large scales and applied stresses, these analyses are often invalid to deduce the behaviour of loosely compacted powders in small quantities and under very low applied loads. In this work we report on our investigations of the flowability of bulk powders using indentation and unconfined compression testing on a small assembly of powders compacted to low pressure levels. Samples of á-lactose fine powders, cohesive glass beads and Magnesium Carbonate have been consolidated to different pressures (ranging from 3 to 16 kPa) and the indentation hardness and unconfined yield stress of the assembles is then deduced. Furthermore Distinct Element Method is used to predict the bulk behaviour of the cohesive powders based on single particle mechanical properties and to provide a means for the interpretation of experimental data.