Introduction of a New Index for the Prediction of Capping Tendency of Tablets

Abstract

Capping within a tablet was quantitatively estimated by using the capping ratio, defined as the ratio of the tablet strength to that of the uniformly compacted tablet. Capping index was also newly defined as the ratio of the extrapolated residual die wall pressure to the binding strength of compacted powder. It was found that capping occurred when the capping index exceeded unity. This fact indicated that capping can be regarded as cracking within a tablet caused by high residual die wall pressure. The requirements to achieve uniform compaction were clarified from these results. It was found that the extrapolated residual die wall pressures of convex-faced tablets were related to those of flatfaced ones. It was also found that tablets consisting of more elastic powders had a lower residual die wall pressure. © 1989, The Pharmaceutical Society of Japan. All rights reserved.