Planar entry converging flow during extrusion of polymer melts

In this article, a planar entry converging flow during die extrusion of polymeric melts was analyzed and a differential equation of entry converging boundary streamline equation with rheological parameters and channel geometry is established. By applying limit theory, the entry converging boundary streamline equation in the case with different non-Newtonian index (n) was discussed, and the corresponding expressions of entry natural convergent half angle and convergent region length were derived. The entrant flow pattern might be described with the half angle of entry natural convergence (alpha(0)) and the convergent region length (L-e) of the melts, and alpha(0) and L-e were mainly a function of the entry elastic storage deformation energy (e) and n. The values of alpha(0) and L-e were calculated by means of these simplified expressions. It was found that the estimations of alpha(0) decrease nonlinearly white L-e increases linearly with an addition of e. Finally, a preliminary verification of the natural converging half angle equation was made. The results showed that the estimations of 2 alpha(0) based on the experiments of a low-density-polyethylene (LDPE) and a high-density-polyethylene (HDPE) were close to the data reported in reference.