Abstract

The kneading effect was studied according to the screw profile of polypropylene (PP)/low-density polyethylene (LDPE) blends. To increase the efficiency of the twin-screw extruder process, the optimal process conditions were set using an extrusion simulation program. After measuring the thermal and rheological properties of the two matrices and entering the material information, the extrusion process was simulated to determine the conditions that maximized the kneading effect. In addition, a screw profile that increases the kneading effect was designed by analyzing the specific mechanical energy, residence time distribution, torque, and temperature change results of the simulation program. After extrusion, the kneading effect of the PP/LDPE blend was analyzed using scanning electron microscopy (SEM), differential scanning calorimetry, and rotational rheometry. The SEM images indicated an increase in the kneading effect between the two matrices, and the shear effect of the material owing to the differences in the screw profiles was determined from the rheological property results. The actual measurements tended to be consistent with the simulation results, and the study of the screw profile design and optimal process conditions using the simulation program effectively improved the kneading effect without material degradation.

Keywords: blending;twin screw extruder simulation;kneading effect;viscosity;screw profile