Flow characterization of a pharmaceutical excipient using the shear cell method

Abstract

The powders used in the production of solid dosage forms must have ability to flow that allows their industrial processing. Although this property has been studied for most of the powders, in this study non-expected flow behaviors were observed for the model excipient used, Microcrystalline Cellulose (MCC). Several fractions with different sizes were fractioned by sieving of the model excipient and its flow behaviors were analyzed by different methods. The shear cell results showed an increase of the flowability index (ff_c) with the increase of the particle size and consolidation stress. Some related information has been referenced in the literature, however, in this work it was shown for different size fractions that the ff_c decreased above a certain consolidation stress value (2000–4000 N/m²). The explanation of this phenomenon is based on the increase of cohesion. Furthermore, it was also observed that the fractions with sizes between 125–180 µm present a ff_c higher than bulk powder (F_Total) with similar percentile (D_V50) indicating that this index is dependent on the size of the particles and also on its size distribution range. Thus, it can be affirmed that more homogeneous samples in size and with a narrower distribution present a better ff_c.

Keywords:

• Flowing
• flow index
• shear cell
• excipient
• sieving

Acknowledgments

The authors would like to thank Dr. Teresa Malta and Atral, S.A., for the kindly offer of the cellulose microcrystalline, that made this work possible.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Applied Molecular Biosciences Unit-UCIBIO which is financed by national funds from FCT/MCTES (UID/Multi/04378/2019).