Studies of converging flows of viscoelastic polymeric melts. II. Velocity measurements in the entrance region of a sharp-edged slit die

An experimental study has been carried out to measure velocities of viscoelastic polymeric melts flowing into a sharp-edged slit die and in the fully developed region of the slit die. For the velocity measurement, the technique of streak photography was used, in which photographs are made of the movement of tracer particles suspended in a molten polymer. Materials investigated were polypropylene, high-density polyethylene, and polystyrene. From the photographs, local velocities in the entrance region were determined by measuring the streak length, a reference length, and the exposure time of the camera. A comparison was also made of the experimentally determined velocity profiles in the fully developed region with the theoretically predicted ones, showing a reasonable agreement between the two.