No abstract

synopsisTwo slit dies have been designed, having aspect ratios of 10 and 20. Three melt pressure transducers were flush-mounted on the long side of the rectangular slot, along the longitudinal centerline of each die. The dies were then used to measure wall normal stresses along the longitudinal direction of polymer melts flowing through the thin slit. The polymeric materials investigated were high-density polyethylene, lowdensity polyethylene, polypropylene, and polystyrene. The measurement of wall normal stresses were used to determine the rheological properties of melts, namely, the melt viscosity from the slope of axial pressure profiles and the melt elasticity from exit pressures. The present study shows that the rheological properties determined from the slit rheometer are in good agreement with those from the capillary rheometer reported in the author's earlier papers. Therefore it may be concluded that a slit die also may be used as a means of characterizing polymeric materials by their viscous and elastic properties in the molten state.

synopsisA slit rheometer described in part I of this series was used for characterizing two blend systems by their viscous and elastic properties in the molten state. The blend systems chosen for study were blends of two high-density polyethylenes having widely different molecular weight distributions and blends of polystyrene and polypropylene which are incompatible in the molten state. The present study shows that blends of two highdensity polyethylenes and blends of polystyrene with polypropylene exhibit a minimum in melt viscosity and a maximum and minimum in melt elasticity (in terms of "exit pressure") a t certain blending ratios. These results confirm the author's earlier findings, which were obtained with a capillary rheometer.