Effects of true density, compacted mass, compression speed, and punch deformation on the mean yield pressure

Compressibility properties of pharmaceutical materials are widely character ized by measuring the volume reduction of a powder column under pressure. E xperimental data are commonly analyzed using the Heckel model from which po wder deformation mechanisms are determined using mean yield pressure (P-y). Several studies from the literature have shown the effects of operating co nditions on the determination of P-y and have pointed out the limitations o f this model. The Heckel model requires true density and compacted mass val ues to determine P-y from force-displacement data. It is likely that experi mental errors will be introduced when measuring the true density and compac ted mass. This study investigates the effects of true density and compacted mass on P-y. Materials having different particle deformation mechanisms ar e studied. Punch displacement and applied pressure are measured for each ma terial at two compression speeds. For each material, three different true d ensity and compacted mass values are utilized to evaluate their effect on P -y. The calculated variation of P-y reaches 20%. This study demonstrates th at the errors in measuring true density and compacted mass have a greater e ffect on P-y than the errors incurred from not correcting the displacement measurements due to punch elasticity.