Hencky strain shifting of convergent flow measured effective elongational viscosity

The effective elongational viscosity data on a series of polyolefins as a function of the Hencky strain are shifted to a reference Hencky strain using an approach similar to that used for temperature shifting, shearing viscosity data. The basis of this shifting is the order that develops (i.e., the decrease in entropy that occurs) during forced flow through sernihyperbolically convergent dies. The entropy decrease is proportional to the orientational contribution to the effective elongational viscosity. The Hencky strain shift factors are obtained from the convergent flow effective elongational rheology and the complex and capillary shear rheology. The commercial grades of polyolefins studied include polypropylene, high density polyethylene, and metallocene and conventionally catalyzed low density polyethylene. The combination of the temperature shift factors given in our companion article and the Hencky strain shift factors in this article enable the creation of master curves for the effective elongational rheology. (C) 2002 Wiley Periodicals, Inc.