The use of bulk density measurements as flowability indicators

Two equipments for measuring the bulk density of powders have been used to assess the flowability of porous and non-porous powders in which particle size changes as a result of controlling the percentage of fine components in the mixtures. The Hosokawa Powder Tester, which measures the aerated and tapped bulk densities, gives accurate measurements of bulk density because a fixed volume of powder is used and the mass of the powder can be measured accurately. On the other hand, the Copley Tap Density Volumeter, which uses a fixed mass of powder, gives inaccurate measurements due to the difficulty of reading the volume from the graduated cylinder. Generally, the flowability of powder increases with the increase of particle size, and there appears to be a critical size range above which flowability does not show any improvement. The packing of particles in two conditions, i.e., aerated and tapped, is examined and compared with the ideal packing of binary mixtures spherical particles. (C) 1999 Elsevier Science S.A. All rights reserved.