Evaluation of the Effects of Liquid Bridges on the Bulk Properties of Model Powders

Measured amounts of water were admixed with uniform size glass beads (107-475 micron) to form model powders with controlled interparticle liquid films. The viscosity of the films was modified by dissolving carrageenan and its surface tension by a detergent. These model powders were tested for loose bulk density, compressibility, irrecoverable work in compaction, cohesion and residual modulus after relaxation. The effect of the films on these bulk characteristics was considerable in the fine model powders but diminished with the increase of particle size. In comparison to particle size, the film viscosity (l-2000 cp) and surface tension (72 and 35 dyne cm−1) had little or insignificant effect on the bulk properties. The results are explained in terms of the internal structure of the bed and their possible implications in real powders are evaluated.