Studies on Fluidity of Powders. VIII

Relationship between Fluidity and Agglomeration

Abstract

In order to find the relationship between agglomeration and fluidity, sliding angle of glass beads in various liquids was measured and the result was considered with the presence or absence of agglomeration judged from sedimentation volume. Glass beads do not undergo agglomeration in hydrous polar liquids like water and hydrous alcohol, and show small sedimentation volume. Sliding angle in such a liquid is approximately constant irrespective of the viscosity, specific gravity, or surface tension of the liquid. On the other hand, glass beads undergo agglomeration in hydrous non-polar liquids like hydrous benzene at ordinary temperature (25°), has a large sedimentation volume, and a large sliding angle. The degree of agglomeration becomes smaller as the liquid temperature rises, even in hydrous non-polar solvent, and the phenomenon is accompanied by decrease in sliding angle. The degree of agglomeration can be predicted to a certain degree by the state of filling by tapping of a liquid and this value also agrees well with that of the sliding angle.
Sliding angle can be considered in two parts; the item that can be determined by the form of filling of particles and that determined from friction coefficient and adhesion force. Values for each of these items were determined for glass beads in air and adhesive force for the beads was calculated. Similar considerations were made for glass beads in liquid.