Three-dimensional viscoelastic numerical analysis of the effects of gas flow on L-profiled polymers in gas-assisted coextrusion

Abstract

Abstract In this study, polymer gas-assisted coextrusion experiments were performed. The influence of a traditional coextrusion flow zone on the gas groove and the relationship between the gas pressure and the melt flow rate were studied. To determine the effects of the gas flow on gas-assisted coextrusion, a three-dimensional simulation was developed in which the gas layer was considered as an independent flow zone. The influence of the gas pressure, gas layer thickness and melt flow rate on the melts’ profile and the deflection deformation degree (DDD) was studied, and the relationship between the gas pressure, gas layer thickness and melt flow rate was obtained. The numerical results indicated that a traditional coextrusion flow zone in front of a gas-assisted coextrusion flow zone could allow products to avoid a gas groove. The quality of the products could be improved by decreasing the gas pressure and gas layer thickness or increasing the melt flow rate. Additionally, the minimum gas pressure decreased as the gas layer thickness increased and increased as the melt flow rate increased. The numerical results were in good agreement with the experimental results, despite a slight quantitative error. Therefore, reasonably controlling the gas flow condition is key in practical applications of gas-assisted coextrusion, and the effects of the gas layer should be considered in gas-assisted coextrusion simulations.