Quantification of tablet sensitivity to a stress concentration: Generalization of Hiestand’s approach and link with the microstructure

Sensitivity to a stress concentration is important for the development of pharmaceutical tablets as it is related to defects like capping. The Brittle Fracture Index (BFI) was introduced by Hiestand et al. to test this sensitivity. Recently, a more general index, based on the average stress criterion, was proposed as a generalized Hiestand approach. In this work, this new approach is tested on tablets obtained for several products and pressure levels, and results show the wide applicability of the new criterion.

Highlights

• The new average criterion to characterize tablet brittleness was successfully applied to a large set of tablets.

• Sensitivity to stress concentration increases when the porosity of the tablet decreases.

• XμCT was used to characterize the tablet microstructure.

• Correlation between the sensitivity to a stress concentration and the size of the largest pores in the structure.

Furthermore, X-ray micro-computed tomography was used to link the tablet microstructure and the sensitivity to a stress concentration. A strong correlation was found between the size of the largest pores in the structure and the value of a₀ which quantify the sensitivity to a stress concentration in the generalized Hiestand approach. These results constitute the first attempt to link the brittle fracture propensity of tablets with their effective microstructure.

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Article Information: Author links open overlay panelB. Croquelois, J. Girardot, J. B. Kopp, P. Tchoreloff, V. Mazel; Powder Technology, 2020.

Keywords Tabletting, Capping, BFIBrittle fracture propensity, Microstructure, XμCT, calcium phosphate dihydrate (DCP) (Dicafos D160, Chemische Fabrik Budenheim Budenheim, Germany), granulated α-lactose monohydrate (MLac) (Excipress, Armor Pharma, France), anhydrous β-latose (ALac) (Duralac, Meggle, Wasserburg, Germany), spray-dried lactose monohydrate (SDLac) (SuperTab 14SD, FSD) and spray-dried mannitol (SDMan) (Pearlitol, Roquette, Lastreme, France).