Abstract: The mixing efficiency in the pin mixing section of a single-screw extruder was evaluated using the normalized mixing entropy. Nine different arrays of the pin mixing section were designed with the orthogonal design method. The isothermal flow field of polypropylene melt in the mixing section was calculated using a finite element method. The effects of the row number in a pitch length, the pin number in each row, and the pin height on mixing efficiency were discussed. It was found that the normalized mixing entropy increased along the extrusion direction. The best mixing efficiency was obtained by a configuration with five rows of five 12 mm high pins in a single screw pitch.

Key words: pin screw, mixing efficiency, numerical simulation, mixing section