Jørn Sonnergaard
Associate Professor, Ph.D.
Pharm.Technology
Department of Pharmacy,
University of Copenhagen

ABSTRACT: A dimensionless index which quantifies the brittle or ductile character of compacted powders is presented. The work of failure (WOF) of crushed or broken flat tablets is calculated by numerical integration of the force-displacement measurement in a flexure tester. The ratio between WOF and the crushing force (F) corrected for the diameter of the tablet (D) is proposed to express the brittle/ductile index (BDI).

This dimensionless index denotes quantitatively the brittle/ductile character of the compacted material as the normalised deformation in per cent of a cylindrical tablet at the breaking point. For ideal brittle materials the BDI value will be 0 and for complete plastic deformation i.e. a total compression of the tablet without fracture BDI will be 100. The validity and discriminative power is demonstrated on mixtures of microcrystalline cellulose and lactose. The robust measure of brittleness with an acceptable accuracy is obtained with only minor influence of tablet diameter and speed of platen.