Extensional flow is one of the common flow patterns in polymer processing, such as melt spinning and entry contraction flow. Extensional viscosity is an important characterization of flow properties for polymeric materials. In this article, temperature T was introduced into H function which represents the destruction rate of network junctions and a new viscosity equation was derived based on Phan-Thien—Tanner model. The elongation viscosities of a high-density polyethylene (HDPE) and a low-density polyethylene (LDPE) melts were estimated using this equation at 150°C, and the calculations were compared with the measured data from the extension experiments of the HDPE and LDPE melts reported in reference. Good agreement was showed between the predictions and the measured data. Furthermore, the parameters in this equation were easy to be determined.
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