Powder flowability as an indication of capsule filling performance

The flowability of size fractions of 5 pharmaceutical excipients has been related to their capsule filling performance. Using angular, packing and shear tests, the samples were ranked in different relative orders of flowability. The powders were filled on an instrumented mG2 capsule filling simulator fitted with a size 1 dosator. Capsule fill weight and weight uniformity were monitored and the coefficient of variation (Xcv) of the fill weight of 20 capsules was used as an indicator of capsule filling performance. Flowability was dependent on the particle size, morphology and bulk density of the powder. There was a significant correlation between the values of Xcv and the flow parameters of Carr's compressibility, Hausner's ratio, angle of repose, Kawakita's equation constant (a) and Jenike's flow factor. Xcv was also related to the coefficient of variation of the powder bed bulk density and the variation in the compression stress. There was, however, no correlation between the values of Xcv and the angle of internal flow and the angle of effective friction.

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