Title: Some practical implications of cohesion in powders physical properties

Author (Invited): Micha Peleg, University of Massachusetts

Abstract:

The properties of cohesive powders, unlike those of free flowing granular materials, are primarily determined by attractive interparticle interactions. They simultaneously affect the powders' bulk density, compressibility, flow pattern, tendency to cake and the type of mixtures that they form. These are known as 'interactive' or 'ordered' mixtures and usually they do not segregate even when there is a large difference in the ingredients' particle size. Nevertheless, there need to be surface affinity between the components for the mixture to hold together. The flow properties of cohesive powders can be improved dramatically by the admixure of very small quantities of anticaking agents, also known as 'anti agglomerants' or 'glidants'. However, when effective, these additives can also affect other properties, especially the bulk density. Contrary to common belief, the addition of anticaking agents cannot protect hygroscopic powders against unimpeded moisture sorption. Selected examples will be given in the form of actual demonstrations.