WETTABILITY PARAMETERS AND DEFORMATIONAL BEHAVIOR OF POWDER-LIQUID MIXES IN THE FUNICULAR AGGLOMERATION PHASE

Wettability of two powdered materials (lactose and sulfadiazine) of si milar particle size is quantified as contact angle, spreading coeffici ents and work of adhesion. On the basis of overwetting tests, performe d in a specially-constructed wet-kneading rheometer, the agglomeration phases are distinguished by recording the resistance to mixing as tor que exerted on the mixing vessel with increasing quantities of differe nt granulating fluids (water, isopropanol, water/isopropanol mixture a nd liquid paraffin). Separate powder-liquid mixing experiments are car ried out, with selected amounts of liquids, and the tensile strength o f the resulting wet masses is measured at different consolidation stat es together with their resistance to densification. It was found :hat both the amount of granulating liquid, corresponding to the mean funic ular agglomeration state, and the deformational behaviour of wet masse s with certain liquid volume fraction, quantified as tensile strength and resistance to densification are related to the work of adhesion bu t only for liquids of similar viscosity. No correlation was observed b etween the torque and the work of adhesion or the viscosity of the gra nulating liquid. (C) 1997 Elsevier Science B.V.