Characterization of the Rheological Behavior of Mixed Miscible Polymers derived from Recycling Processes

Mechanical recycling of polymers often involves mixing polymer types with the same chemical structure but different properties, e.g., two PP grades with different melt flow rates. The change in the physical properties is of great interest. In this study, the rheological behavior of two types of virgin PP and blends of these with different weight fractions were studied using high-pressure capillary rheometry. A new method that considers the shear-rate-dependent viscosity based on the shear stress is presented. The method allows to consider various mixing rules. Four existing mixing rules to predict the viscosities of mixed miscible polymers were applied. The comparison of the predicted values to experimental investigations shows that the application of the mixing rule of Arrhenius, which is also known as the rule of Bersted delivers the most accurate results. The mean absolute deviations are between 3.38% and 5.06% for all models. Tendentially the predicted values are slightly below the measured values, especially at high shear rates.