AN ASSESSMENT OF SUBSTRATE-BINDER INTERACTIONS IN MODEL WET MASSES .1. MIXER TORQUE RHEOMETRY

Recent work has shown the importance of physical interactions between materials during size enlargement processes (e.g., wet granulation). In this study several model substrates and binder solutions were selected, their particulate, solution and energetic properties determined and the potential physical interactions of the solid and liquid phases assessed. Considerable differences were noted in the wetting, spreading and adhesion tendencies of the various substrate-binder combinations. The rheological properties of the wet massed solid-liquid systems were then measured using an instrumented mixer torque rheometer. The results confirmed that solid-liquid physical interactions (especially spreading) are important in determining wet massing behaviour. The most important influences appeared to be on the stability of the wet masses at elevated liquid levels and theories were developed to explain this observation in terms of the accepted models of wet granule structure.