Compaction of crystallographic forms of pharmaceutical granular lactoses. II. Compacts mechanical properties.

It is well known that the choice of the crystal form affects the physicochemical properties such as compaction behaviour. In this work, the mechanical properties of compacts obtained from compaction of lactoses by using a micropress prototype are calculated. Tensile strength, Young's modulus, toughness and Brinell hardness were measured and used to compare the various crystalline forms: alpha-lactose monohydrate (LalphaM), anhydrous beta-lactose (LbetaA), anhydrous alpha-lactose (LalphaA) and partly amorphous lactose (FF). With all the mechanical properties measured, the lactoses could be differentiated. Then, the specific energy of failure G*(IC) was obtained from the toughness and the Young's modulus for each lactose. LalphaM showed small specific energy of failure due to its low toughness which is not balanced by its Young's modulus. The highest values were obtained with the two anhydrous forms, LalphaA and LbetaA. Finally, these mechanical properties were linked with general compaction behaviour and cohesive energy density which is a characterization at a molecular level.