Profile extrusion die design: A comparative study between elastic and inelastic fluids

Abstract

Computational modeling is widely used to support the design of profile extrusion dies. However, despite the viscoelastic nature of the polymer melts, the majority of the computational approaches resort to inelastic models. With the aim of assessing the accuracy of the approach usually employed on the modeling of profile extrusion dies, this work aims at comparing the behavior of profile extrusion dies when interrelated viscoelastic (elastic) and generalized Newtonian (inelastic) constitutive models are used. For this purpose, the polymer melt employed in the study was experimentally characterized, being the data collected used to fit a nonlinear multimode viscoelastic (elastic) Giesekus constitutive model. Subsequently, the fitted model was used to generate the material shear flow curve, which was then used to fit a Bird-Carreau (inelastic) constitutive model. The numerical studies undertaken were focused on the extrusion die of two profiles: a simple one, with a rectangular cross-section, and a complex swimming pool cover profile. The results obtained showed that in realistic case studies, the effect of elasticity might be relevant, even when modeling just the flow in the extrusion die flow channel and, thus, should be considered when designing profile extrusion dies.