A novel experimental–numerical procedure for the rheological characterization of thermoplastic polymers applied to injection molding

Products’ quality in injection molding (IM) is affected by several factors, thus motivating the use of numerical models and codes for process optimization. One of the most affecting properties from the modelling perspective is the polymer rheological behavior. This work aims therefore to present a novel rheological characterization procedure based on Melt Flow Index (MFI) test, which offers the advantages of reduced costs and simplicity of execution if compared to capillary rheometers. The Cross-WLF viscosity model was selected to fit the experimental data, while a novel procedure based on the Melt Flow Index test’ numerical simulations was implemented to correct the experimental rheological curves by reducing the errors in terms of the pressure applied to the molten polymer during the MFI tests. The methodology was used to characterize a polyamide 6 filled with 30% of glass fibers (PA6GF30) employed for the manufacturing of a saw body by IM. By simulating the process with the optimized viscosity curves, the experimental–numerical comparisons in terms of injection pressure, deflection, and fibers orientation tensors showed a good agreement with peak errors of 0.2%, 1.6%, and 7.9%, respectively. In addition, to validate the proposed approach, the obtained curves were compared to those acquired by the conventional method of the capillary rheometer, and a good match was found between the curves from the two methodologies.