The relationship between granule growth mechanism, amount of liquid binder added and properties of the wet powder mass determined using a split bed shear tester

Abstract

The Peschl-split bed shear tester was utilised to study the formation of different liquid states during wet massing for granulation. Using lactose monohydrate as a model bulking agent the threshold between pendular and funicular state was found to be at about 6% (w/w) of liquid binder added to the wet mass, here a 5% colloidal solution of HPMC in water. The upper limit of the funicular state appeared to be at approximately 15% (w/w) of liquid binder. The threshold values obtained from the shear cell measurements did correlate with values obtained from dried granule characteristics such as granule density and compressive Young’s modulus determined by Dynamic Mechanical Analysis. The compressive Young’s modulus increased with an increasing density of the wet mass during the shear experiments and decreased with an increase in the angle of internal friction. The results suggest that stiffer granules were a result of densification, not the strength of liquid bridge bond formation.