Mechanical characterization of tablets using post compression in-die cyclic loading

Abstract

The purpose of this work is to use post compression in-die cyclic loading as an analytical powder compression tool. Cyclic loading experiments (partial unloading followed by reloading) were performed on tablets formed from three relatively coarse powders (∼100μm) comprised of microcrystalline cellulose (MCC), ibuprofen (IBU) and lactose monohydrate (LAC). The reloading curve was always linear initially, irrespective of the shape of the unloading curve. Hence, nonlinearities in the unloading curve should be attributed to inelastic phenomena rather than to nonlinear elasticity. The slope of the reloading curve generally decreased with increasing degree of unloading, indicating a progressive damage of the contact network upon unloading. For MCC and IBU, consistent unloading curves following primary and secondary loading were obtained. For LAC, the secondary unloading curves were displaced towards smaller tablet heights, suggesting that that particle fragmentation occurs during unloading and reloading, also when the maximal tableting pressure is not exceeded.