Pharmaceutical powders compaction: Experimental and numerical analysis of the density distribution

This paper investigates the axial density distribution during the single action compaction of pharmaceutical powders in rigid dies. Experimental results of the compaction of microcrystalline cellulose are compared to those predicted with an analytical model and with numerical analysis. The axial density distribution within tablets compacted at different loads are measured using a mercury porosimeter of slices from tablets. The analytical model based on the Janssen-Walker analysis coupled with the Heckel equation is applied to determine the axial density distribution. Representing the mechanical behaviour of the powder compaction with the Drucker-Prager/Cap model and by measuring the die wall friction, computation of the axial density within the tablet is also obtained by solving the boundary problem with finite element method for the loading-unloading cycle. Results of the axial density obtained with the analytical model and numerical method at end of the loading step show a qualitative agreement with the measured data. However, the measurements are better predicted with the numerical results obtained with the simulation of the loading-unloading phases. (c) 2005 Elsevier B.V. All rights reserved.