POWDER DENSIFICATION - 2 - VISCOELASTIC MATERIAL PROPERTIES IN MODELING THE UNIAXIAL COMPACTION OF POWDERS

A micromechanical model for predicting the densification of particulat e matter under hydrostatic loading was developed to account for the ti me-dependent response of materials to applied loads. Viscoelastic mate rial response used in the analysis was based upon a standard three-par ameter rheological model. Compaction data under closed die conditions were collected using an Instron analyzer for different rates of applie d load. Densification during the loading phase of PMMA/coMMA powder, a pharmaceutical polymeric coating material, was well predicted by the proposed algorithm, which contrasts with the prediction implied throug h a static indentation model. Secondary factors which affect compactio n such as die-wall friction are also briefly discussed.