Characterization of microcrystalline cellulose and silicified microcrystalline cellulose wet masses using a powder rheometer

A powder rheometer has been used to study the properties of wet powder mass es and the results have been compared to the mixer torque rheometer (MTR). Two different microcrystalline cellulose (MCC) grades (Avicel and Emcocel) and silicified microcrystalline cellulose (SMCC, Prosolv) were used as mode l powders. The wet massing behaviour of one material (Prosolv) was studied by the powder rheometer using liquid addition experiments, while the theolo gical properties of wet granules were studied using both the powder rheomet er and the MTR. In water addition measurements the torque behaved in a simi lar way to MTR measurements and the maximum value of ZTL (zero torque limit ) was achieved at the capillary state of wet mass. The wet granules exhibit ed different behaviour in the powder rheometer and the MTR experiments. whi ch indicates that these rheometers involve different shear forces or they m easure different properties of the wet granules. Emcocel wet masses achieve d the capillary state at lower liquid amount than Avicel and Prosolv masses , which indicates that Emcocel is not able to hold as much water in the int ernal structure as Avicel and Prosolv. The powder rheometer proved to be a sensitive piece of equipment, which can be used to study both dry and wet p owder masses. It was able to distinguish wet granules from wet powder masse s after liquid addition. whereas the MTR could not. However, before the pow der rheometer can be properly utilised in wet powder mass studies, the prob lem of torque overload requires resolution. (C) 2001 Elsevier Science B.V. All rights reserved.