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Evaluation of ring shear testing as a characterization method for powder flow in small-scale powder processing
Søren Vinter Søgaard1, Troels Pedersen1, Morten Allesø2
1Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
International Journal of Pharmaceutics
|September 3, 2014
Summary
Understanding powder flow in pharmaceutical manufacturing is crucial. This study reveals that powder flow properties significantly depend on consolidation stress, impacting tablet press operations and requiring improved testing methods for accuracy.
Area of Science:
- Pharmaceutical Engineering
- Materials Science
- Chemical Engineering
Background:
- Predicting powder flow in small-scale pharmaceutical equipment is difficult.
- Consolidation stress significantly influences powder behavior during flow.
- Accurate characterization is essential for pharmaceutical manufacturing processes.
Purpose of the Study:
- Investigate the impact of consolidation on powder flow characterization.
- Determine consolidation levels during tablet press hopper discharge.
- Assess the uncertainty in shear and wall friction measurements at low stresses.
Main Methods:
- Utilized three grades of microcrystalline cellulose for testing.
- Measured consolidation during powder flow characterization.
- Analyzed shear and wall friction under varying consolidation stresses.
Main Results:
- Powder flow properties are highly dependent on consolidation during testing.
- Observed consolidation stresses during hopper discharge were approximately 200 Pa (major principal stress) and 114 Pa (wall normal stress).
- Identified lower consolidation limits for shear (500 Pa) and wall friction (200 Pa) tests, where stress resolution impacts precision.
Conclusions:
- Powder flow characterization requires careful consideration of consolidation levels.
- Current experimental setups may lack the necessary resolution for accurate measurements at low consolidation stresses.
- An improved experimental setup with high shear stress resolution is needed to enhance the accuracy and applicability of powder flow tests in pharmaceutical applications.
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