Measuring static and kinetic friction in routine compaction cycles and their implication for formulation development

July 05, 2024 - by Danny van der Haven , Quentin Boulay

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The ejection of pharmaceutical tablets from the die is a critical moment after compaction during which defects can be induced if frictional forces are too high. Various studies have looked at the maximum force, static friction coefficient, and kinetic friction coefficient during ejection. However, all of these have distinct physical meanings and therefore also different consequences for formulation development. Moreover, particularly the measurement of friction coefficients is non-trivial and often requires approximations.

In this study, we present a novel method to accurately and conveniently measure the ejection force, static friction, and kinetic friction during routine compaction cycles using the STYL’One Evo compaction simulator. Using this new method, we present a systematic study considering variations in ejection speed, compaction density, excipient material, and lubrication method. Results show that the new method is in agreement with established literature and provided new guidelines for developing low-friction formulations to avoid potential tableting defects.

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Agenda

MEDELPHARM introduction and instrumented die presentation for the measurement of radial die wall pressure
Scientific insights from Danny van der Haven, PhD student from University of Cambridge
Q&A session

Key learnings

Both the static and kinetic friction coefficients can be measured during regular compaction cycles using a STYL’One compaction simulator
Kinetic friction is mainly influenced by the ejection speed and the lubricant, showing only a weak dependence on the excipient material
Very soft as well as very hard materials can lead to high ejection forces and friction coefficients

van der Haven, Dingeman LH, et al. "Tablet ejection: A systematic comparison between force, static friction, and kinetic friction." International Journal of Pharmaceutics 661 (2024): 124369. https://doi.org/10.1016/j.ijpharm.2024.124369

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Tablet ejection: A systematic comparison between force, static friction, and kinetic friction

About the speaker

Danny van der Haven

Dingeman (Danny) van der Haven is a PhD student at the University of Cambridge in the Macromolecular Materials Lab of Prof. James Elliott. He studies the compaction process of pharmaceutical powders into tablets with a focus on developing new methods for the prediction and measurement of the mechanical properties of new formulations. Despite an emphasis on computational methods, using the finite element method (FEM) and discrete element method (DEM), his work remains closely related to practical applications and is extensively validated through experiment.