BINDER-SUBSTRATE INTERACTIONS IN WET GRANULATION .1. THE EFFECT OF BINDER CHARACTERISTICS

A laboratory-scale, instrumented mixer torque rheometer has been used to examine the interactions of microcrystalline cellulose with aqueous solutions of two polymer binders. The rheological behaviour indicated differences, at equivalent viscosity, between the two polymers, which were explained by theories relating binder surface tension to granule properties. The measured surface tension values were then used to calculate the surface free energies, interfacial works of cohesion and adhesion and spreading coefficients for the interaction between the materials used in this study. These data indicated a different degree of interaction between the two polymers and the cellulose substrate, which was probed further using a series of experiments to examine polymer adsorption phenomena. These combined data were used to propose a pattern of behaviour based on consideration of 'intra-granular viscosity' which helped to explain the observed rheological behaviour. © 1990.