Effects of shear cell size on flowability of powders measured using a ring shear tester
2022
Wang, Chenguang | Song, Sichen | Gunawardana, Chamara A. | Sun, David J. | Sun, Changquan Calvin
Flowability parameters of powders measured by a shear cell is expected to depend on shear cell size, but details of that effect are lacking. In this work, we have systematically evaluated this using a number of powders under three preshear normal stresses using a ring shear tester. The flowability index (ffc) of a limestone powder (BCR 116) exhibited relatively small differences when measured on three shear cells of different sizes, S (~9.5 cm³) < M (~30 cm³) < L (~70 cm³). However, significant differences in measured ffc of common pharmaceutical powders were observed, where ffc of powders with a median particle size >22 μm was more than 15% higher using S than M. Large differences between data from M and L were found for powders with a median particle size >125 μm. Therefore, one must exercise caution when comparing flow properties of powders characterized using different shear cells.
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