Evaluation of ring shear testing as a characterization method for powder flow in small-scale powder processing equipment

Research output: Contribution to journalJournal articleResearchpeer-review

Søren Vinter Søgaard, Troels Pedersen, Morten Allesø, Joergen Garnaes, Jukka Rantanen

Powder flow in small-scale equipment is challenging to predict. To meet this need, the impact of consolidation during powder flow characterization, the level of consolidation existing during discharge of powders from a tablet press hopper and the uncertainty of shear and wall friction measurements at small consolidation stresses were investigated. For this purpose, three grades of microcrystalline cellulose were used. Results showed that powder flow properties depend strongly on the consolidation during testing. The consolidation during discharge in terms of the major principal stress and wall normal stress were approximately 200Pa and 114Pa, respectively, in the critical transition from the converging to the lower vertical section of the hopper. The lower limit of consolidation for the shear and wall friction test was approximately 500Pa and 200Pa, respectively. At this consolidation level, the wall and shear stress resolution influences the precision of the measured powder flow properties. This study highlights the need for an improved experimental setup which would be capable of measuring the flow properties of powders under very small consolidation stresses with a high shear stress resolution. This will allow the accuracy, precision and applicability of the shear test to be improved for pharmaceutical applications.

Original languageEnglish
JournalInternational Journal of Pharmaceutics
Volume475
Issue number1-2
Pages (from-to)315-323
Number of pages9
ISSN0378-5173
DOIs
Publication statusPublished - 29 Aug 2014

ID: 123665724