Identifying Robust Parameters for Flowability Analysis of Pharmaceutical Powders Using the Shear Cell Method.

Area of Science:

• Pharmaceutical Sciences
• Materials Science
• Chemical Engineering

Background:

• Powder flowability is essential for pharmaceutical manufacturing, impacting robustness and content uniformity.
• Shear cell measurements provide parameters for predicting powder behavior but often depend on consolidation conditions.
• A need exists for an intrinsic flowability parameter independent of external factors for better quality control and formulation.

Purpose of the Study:

• To investigate the relationship between shear cell parameters and consolidation conditions for pharmaceutical powders.
• To identify a robust, intrinsic parameter that accurately reflects powder flowability.
• To assess the influence of particle size and shape on powder flowability parameters.

Main Methods:

• Performed constant-volume shear cell measurements on pharmaceutical powders with varying particle sizes and shapes.
• Analyzed the relationship between shear cell parameters and different consolidation conditions (indentation load).
• Identified and evaluated the critical state line slope (ϕCSL) as a potential intrinsic flowability parameter.

Main Results:

• Preshear points aligned on a single straight line through the origin for a given powder substance, irrespective of indentation load, particle size, or shape.
• The critical state line slope (ϕCSL) demonstrated robustness and insensitivity to particle size and shape variations.
• Deviations in ϕCSL for fine powders (<10 µm) suggest the influence of interparticle cohesive forces.

Conclusions:

• The critical state line slope (ϕCSL) can serve as a reliable intrinsic flowability parameter for pharmaceutical powders.
• ϕCSL offers a robust measure for quality control of raw materials and efficient formulation design.
• Interparticle cohesive forces become significant for fine powders (<10 µm), affecting their flowability characteristics.