A melt flow index-based approach for the viscosity curves determination

To optimize the polymers processing technologies, a rheological characterization of the polymer is essential to predict its behavior at specific temperatures and under varying shear rates. Simulating this process requires providing the simulation software with viscosity curves for the polymer to be processed, ensuring a reliable simulation. However, traditional rheological characterization utilizing a capillary rheometer is known for its high cost, time-intensive nature, and the need for skilled operators. In this study, a more cost-effective approach is proposed, using the Melt Flow Indexer (MFI) to obtain the experimental viscosity curves. These undergo an innovative numerical procedure based on simulating the MFI tests, reducing the numerical-experimental error in terms of pressure applied to the molten polymer. This methodology is applied to characterize three different thermoplastic polymers: polypropylene, 30% glass-reinforced polypropylene and 30% glass-reinforced polyamide. The viscosity curves obtained through this methodology are then compared to those obtained using the capillary rheometer, serving as a reference to assess the accuracy of the proposed approach.