Experimentation, identification, and simulation of polymer swelling at extrusion die outlets

The behavior of polyamide PA12 melt extrudates at die outlets is modeled to determine swelling process and rate. It is assessed as a function of imposed input parameters, process parameters, and die geometries. The modeling is carried out using Comsol Multiphysics (R) platform to simulate the swelling; in particular, its progression in time is investigated for different extrusion process parameters. The experimental swelling observed in extrusion lines tests is compared with the Tanner and Carreau-Yasuda rheological models. A database is built up with all experiments carried out; the comparison between numerical and experimental results shows close agreement. A parametric analysis of the experimental and numerical swelling is performed. It confirms the important role of the die diameter on swelling rate, independently of shear rate. Increase in temperature lowers swelling rate at constant shear rates and geometric aspect ratio of the dies.Highlights Experimental and numerical study of polymer swelling at capillary die outlets. Behavior of PA12 polymer extrudate modeled to determine its swelling. Rheological models implemented to simulate the swelling phenomenon. Simulation results validated with experimental tests for two millimetric dies. Influence of die geometrical parameters investigated and justified. Analysis, physical and numerical modeling, 3D numerical simulation of polyamide PA12 melt swelling at extrusion die exit. Comparison with experiments at different operating pressures and shear rates. image