Computer Aided Design of Coat-Hanger Die in Polymer Film Processing

With the aid of computer simulations, coat-hanger die was designed for more uniform residence time distribution. Analysis of velocity distribution and flow path line indicate that stagnation areas exist in the coat-hanger die, which is caused by the geometry abrupt change between the circular section manifold and the rectangular section slot gap. The stagnation areas affect the melt residence time directly. After changing the circular section manifolds to tear-drop section manifolds, the stagnation areas decrease from 8.21 mm(2) to 5.40 mm(2). Compared with the melt residence time in circular section manifolds, both the maximum residence time and the residence time dispersion were decreased.