Measuring the Flow Functions of Pharmaceutical Powders Using the Brookfield Powder Flow Tester and Freeman FT4

Mark Leaper

doi:10.3390/pr9112032

Abstract

This study examined the feasibility of combining data from different powder flow testers to determine the flow function characteristics of pharmaceutical powders. The Brookfield PFT and Freeman FT4 can measure flow function over different scales of consolidation load but were found to be most complementary with CRM limestone powder and lactose. The brittle behaviour of Easytab particles at higher loads made obtaining repeatable results with the FT4 challenging. By using the method of Wang et al., where the flow function coefficient ffc is plotted against the dimensionless cohesion C* (measured cohesion Ta divided by the initial compaction I), a plot was formed which could be used to predict the behaviour of other systems, which compared well with previous studies.

Highlights

Measuring the flow characteristics of powders in a meaningful way is a significant challenge in comparison to characterising other materials, but is essential if processes and products are to be optimised without the generation of waste or excessive use of energy
The first method for doing this was the Jenike shear cell [1], which measured the movement of pre-consolidated planes of powder over each other whilst experiencing a normal load to construct a series of yield loci; these could be used to plot the flow function, which allowed the design of a suitable hopper and a quantitative comparison of samples compacted under different conditions
8 compares the flow functions of CRM limestone measured by the Brookfield

Summary

Introduction

Measuring the flow characteristics of powders in a meaningful way is a significant challenge in comparison to characterising other materials, but is essential if processes and products are to be optimised without the generation of waste or excessive use of energy. The first method for doing this was the Jenike shear cell [1], which measured the movement of pre-consolidated planes of powder over each other whilst experiencing a normal load to construct a series of yield loci; these could be used to plot the flow function, which allowed the design of a suitable hopper and a quantitative comparison of samples compacted under different conditions Variations of this test included time consolidation, where the powder was loaded for a significant amount of time prior to the test, and wall friction, where the movement of the powder across different surfaces was measured to provide data on silo design. The generation of powder flow analysers include rotational shear cells and uniaxial and multi-axial compression testers; these have been compared and contrasted by Schwedes et al [2]

Methods

Results

Conclusion