Particulate Systems Analysis 2005 - Paper Abstract
Measuring the flow properties of consolidated, conditioned and aerated powders - a comparative study using a powder rheometer and a rotational shear cell
This paper compares powder flowability measurements using the two methodologies available from a Freeman FT4 Powder Rheometer. The twisted blade method is empirical and measures the energy needed to establish dynamic or three dimensional flow patterns at specific packing conditions. The other is an automated shear cell in which the powder sample is sheared across a single plane to determine its shear strength properties. Six different powders were evaluated to determine their flow performance when consolidated, conditioned and aerated or fluidised. Objectives were to correlate the data from the two methods and assess the sensitivity to some of the key variables that affect powder flow properties.
The results showed good correlation of both methodologies regarding conditioned or non-consolidated powder behaviour, but suggests that for consolidated powders, shear strength data is only one of the factors affecting dynamic flow properties, compressibility being another key variable. Aerated powders could not be evaluated with the shear cell, but were assessed using the dynamic methodology and showed very significant differences of flow energy.
In conclusion both methodologies provide useful insights into flow behaviour and both have the sensitivity and repeatability of measurement, but dynamic data provides better differentiation between powders with similar rheological properties in all packing states.
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