Entropic characterization of distributive mixing in polymer processing equipment

Abstract

Abstract Mixing is an integral component of most polymer processing operations as material properties are highly influenced by the quality of mixing. The degree of distributive mixing (system homogeneity) is assessed by calculating the evolution of Renyi relative entropies for the minor component along a continuous processing equipment. The Renyi entropy involves a β parameter, which represents weighting given to the concentration of the minor component in small, localized regions. Different aspects of mixing can thus be analyzed, from the amount of void spaces to the concentration of the region where mixing is the worst in terms of the minor component. This method provides a unified, rigorous and flexible way of characterizing distributive mixing. Specifically, distributive mixing is analyzed in a numerical simulation of a twin‐flight single screw extruder by using particle tracking as a method of describing the mixing process dynamics. Renyi entropies are used to examine three different processing conditions in a twin‐flight, single screw extruder. By changing the throttle ratio, the optimal extruder length varied. The relationship between the optimal length and average residence time was good.