Comparison of Methods for Evaluation of Friction During Tableting

Abstract

The friction between a tablet and the die wall can be evaluated by comparison of the forces on the upper and lower punches, i.e. force ratio (R-value) or force difference (FD, or by measuring the forces on the lower punch immediately before ejection (REF) or during ejection (EJF). These parameters were compared for different materials using an instrumented single-punch press. The compaction load and the dimensions of the compact had an obvious influence on all parameters studied. By correcting for differences in contact area between tablet and the die wall it appears possible to eliminate the influence on FD, REF and EJF from variation in tablet height. Several compaction loads within the range of interest have to be studied to get a complete picture of the behaviour of a tablet granulate. The different parameters did not always give correlating results and EJF appears to give the best prediction of adhesion problems.