A comparison of the axisymmetric and planar elongational viscosities of PE-LD

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The elongational viscosities of a low density polyethylene in axisymmetric and planar flows are compared. The experimental data on entrance pressure loss is matched with the corresponding finite element predictions to estimate the parameters in the elongational viscosity model proposed by Sarkar and Gupta. The entrance losses in the capillary and slit rheometers are used to predict the elongational viscosities for axisymmetric and planar flows respectively. The power-law region of the axisymmetric as well as planar elongational viscosity is found to follow the time-temperature superposition principle. The vortices encountered in the flow near the abrupt contraction for the planar and axisymmetric cases are compared. The vortex near the abrupt contraction is found to reduce in size as the flow rate is increased for planar as well as axisymmetric entrance flow.

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International Polymer Processing