Characterization of wet masses using a mixer torque rheometer: 2. Mixing kinetics

Abstract

An instrumented, laboratory-scale mixer torque rheometer has been used to measure the rheological properties of a range of model and typical pharmaceutical wet massed systems. The mixing torque was monitored as a function of the mixing time from the point of liquid addition until an equilibrium rheological state had been attained. In each system the mechanisms and kinetics of mixing varied according to the saturation of the wet mass and the identity of the substrate and binder components. Although the torque variation was different for each wet massed system an equilibrium rheological state was eventually attained in each case. Measurement of this equilibrium torque response should allow the comparison of different wet masses irrespective of their processing histories.