A new brittleness index for compacted tablets.

A dimensionless index that quantifies the brittle or ductile character of tablets 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). [Formula: see text] This dimensionless index quantitatively denotes the brittle/ductile character of the compacted material as the normalized deformation in percentage of a cylindrical tablet at the breaking point. For ideal brittle materials, the BDI value will be 0 and for complete plastic deformation, that is, 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 a minor influence of the tablet diameter and the speed of platen.