Effects of gas-assisted technology on polymer micro coextrusion

Abstract

Abstract In this paper, a three-dimensional viscoelastic flow model of double-layer micro coextrusion with circular cross-section was established. The simulations were carried out by the finite element method and the influence of wall slip coefficient on micro coextrusion was studied. The results show that gas-assisted technology is suitable for polymer micro coextrusion forming. The differences between the gas-assisted and conventional micro coextrusion process were compared by analyzing the distribution of melts velocity, pressure, shear rate and first normal stress difference. The research results show that in the conventional micro coextrusion process there are pressure drop, shear rate, first normal stress difference and secondary flow. And there is a gradient distribution of melts velocity. The die swell and deformation vary with the forming process parameters, and it is difficult to control the product quality. But in the gas-assisted micro coextrusion process, there is no pressure drop, shear rate, first normal stress difference and secondary flow. The velocity of polymer melts is evenly distributed and the melts are extruded in a plunger shape. The melts do not swell and deform and it is independent of forming process parameters. It is easy to ensure the products quality and the inherent problems of polymer conventional micro coextrusion are well solved.