Application of giesekus model for capillary extrusion of rubber compound

Abstract

Extrudate swell is an important phenomenon occurring when high viscoelastic materials, such as rubber and rubber compounds, are extruded. In this work, the effects of relaxation time and relaxation mode on swell predictions using a nonlinear differential viscoelastic model, that is, the Giesekus model, are studied systematically for rubber extrusion in a capillary die. The corresponding 3D, steady-state finite element simulation for predictions of swelling is presented and compared with experimental data for validation. Velocity distribution, pressure drop and circulation flow in the die are analyzed and discussed through the simulation. The results of swell prediction reveal that three-relaxation mode of the Giesekus model with a wide range of relaxation times reproduce experimental data. In addition, the number of relaxation mode and relaxation time have remarkable effects on circulation flow at the die corner and some effect on other field variables.