Adhesion of Tablets in a Rotary Tablet Press I. Instrumentation and Preliminary Study of Variables Affecting Adhesion

This study describes instrumentation to Measure the adhesion of tablets to the lower punch face by means of a strain gaged cantilever beam affixed to the feed frame in front of the sweep-off blade. The tablet is detached from the lower punch by striking this blade. The adhesion force is the total force measured by the beam less that due to the momentum of the tablet. Tableting was performed on a Stokes RB-2 press previously instrumented to monitor compression and ejection forces. Generally, the higher the compression force, or the lower the magnesium stearate concentration, the higher the adhesion in three direct compression fillers (compressible sugar, microcrystalline cellulose, lactose). With microcrystalline cellulose (0.1% magnesium stearate), adhesion decreased with Increased tablet thickness or decreased tablet diameter (constant thickness) ac constant compression pressure Simultaneous measurement of ejection forces revealed that differences in true lubricant efficiency did not necessarily reflect differences in adhesion. The ability to distinquish differences in adhesion offers promise in assisting in the rational design of tablet formulations.