Use of a capillary rheometer to evaluate the rheological properties of microcrystalline cellulose and silicified microcrystalline cellulose wet masses

The influence of microcrystalline cellulose (MCC) type and water content on the rheological properties of the wet powder masses were studied using two different MCC grades (Avicel and Emcocel) and silicified microcrystalline cellulose (SMCC. Prosolv). A ram extruder was used as a capillary rheometer and unique flow curves for each cellulose grade and moisture content were derived. In addition, the elastic parameters of recoverable shear and compl iance were determined. From different flow curve models evaluated, it was n ot possible to obtain clear evidence, which model best described the rheolo gical properties: of each cellulose grade at each water level. Furthermore, the residuals were shear rate dependent. which indicates that the models d o not perfectly agree with physical properties of the wet masses. The elast ic properties of wet masses increased with increasing water content and dec reased with increasing shear stresses. SMCC grade proved to be more elastic than the simple MCC grades at each moisture content. Thus, the rheological properties of MCC and SMCC wet masses were different and changed with wate r content. Consequently, it was not possible to achieve similar rheological properties between different grades of cellulose by altering the: water co ntent of the wet mass. (C) 2001 Elsevier Science B.V. All rights reserved.