EVALUATION OF RHEOLOGICAL PROPERTIES OF NON-NEWTONIAN FLUIDS IN INTERNAL MIXERS - AN ALTERNATIVE METHOD BASED ON THE POWER-LAW MODEL

A new method was developed to evaluate rheological properties of polym er melts such as shear stress, shear rate, apparent viscosity and othe r rheological parameters in internal mixers. It is based on the classi cal power law model where the power law index n is directly evaluated from a set of data containing speed S, torque M, and the consistency i ndex m is indirectly determined by an empirical relation. The method i s based on a model with only one geometrical parameter (alpha), which involves a chamber radius R-2 and an equivalent radius R-e. It is assu med that the measuring head consists of two adjacent sets of coaxial c ylinders. This method has advantages over previously reported models t hat use two parameters and do not propose a straightforward method to evaluate m The pseudoplastic nature of the polymer melt decreases as t he rate of loss of structural points, i.e., molecular entanglements an d network junctions, increases, which produces greater mobility of the melt. A relationship between alpha and C(n) is found, which is simple r than other models previously reported. These results further demonst rate the feasibility of evaluating rheological properties of polymer m elts in internal mixers.