Initial Results of a Flow Birefringence Study of the Hole Pressure for Polymer Melts
The initial results of this study on a polymer melt shows that, for the present experimental conditions, stress field asymmetry has a negligible effect on the validity of the HP theory and that the theory may be extended to yield a method [i.e., Eq. (2)] by which values of N1 may be calculated directly and accurately from slit die PH and σω data. Additional work is needed, however, to determine the range of conditions for which this is true. Current research efforts are being directed toward determining the effects of slot dimensions, rounding of slot corners, and melt rheological properties on stress asymmetry and the corresponding effect on the magnitude of PH and the predictions of the HP theory.