Partic. vol. 31 pp. 69-79 (April 2017)
doi: 10.1016/j.partic.2016.04.006

Glidant effect of hydrophobic and hydrophilic nanosilica on a cohesive powder: Comparison of different flow characterization techniques

Ahmad Fahmi Bin Ruzaidi, Uttam Kumar Mandal, Bappaditya Chatterjee^*

bdpharmaju@gmail.com

Abstract

The methods used for flow characterization of a powder mass include the angle of repose (AOR), Carr index (CI), and powder flow tester (PFT). The use of nanosilica as a flow modifier (glidant) is very common in industry. This study aims to compare the glidant effect of hydrophobic and hydrophilic silica on a poorly flowable active pharmaceutical ingredient (ibuprofen) by different flow characterization techniques. Different percentages (0.5, 1.0, and 2.0 wt%) of both types of mixed silica–ibuprofen powders were evaluated by the AOR, CI, bulk density, and PFT. The flow factor, effective angle of friction, and cohesion were determined to explain the bulk powder properties. The results show that different types of silica show different levels of flow property improvement, but the techniques do not equally discriminate the differences. Hydrophobic silica results in better improvement of the flow property than hydrophilic silica, probably because of its better surface coverage of silica on the host particles. Change of the bulk density with applied pressure was significant for the different powders. This study demonstrates that combining several characterization methods provides a better understanding of bulk powder flow properties with respect to powder–process relationships than a single flow indicator.

Graphical abstract

Keywords

Silica; Flow measurement; Shear flow tester; Cohesion; Effective angle of friction; Bulk density