Abstract: A three-dimensional non-isothermal viscoelastic numerical simulation nodel with Phan-Thien and Tanner（PTT）constitutive equation was established for two-layer L-shaped coextrusion profile. Arrhenius equation was used to relate the viscosity with temperature. The coextrusion processes of polypropylene（PP）and polystyrene（PS）were investigated by finite element method. The distribution of velocity and shear rate at die exits, die swell, and deformation was discussed in different proportions of the two materials. Calculation results revealed that the die swell and deformation were affected by viscosity ratio as well as the cross section of the die. The deflection from the lower viscous PP to the higher viscous PS was observed and the PP trends to encapsulate the PS. The die swell and deformation when the lower viscous PP was in the inner side were larger than that of PP in the outer side, and the died swell and deformation gap between this two situations increased with increasing viscosity ratio.

Key words: profile, coextrusion, non-isothermal condition, viscoelastic flow, die swell, numerical simulation