Measurement of the Axial Pressure Distribution of Molten Polymers in Flow Through a Circular Tube

Abstract

Axial pressure distributions for the flow of molten polyethylene and polystyrene has been obtained at shear rates of from 100 to 500 sec −1 . In the case of polyethylene, fully developed flow was obtained within a length equivalent to one tube diameter ( 1 8 in.). The extrapolation of the polyethylene pressure profile revealed a normal stress (radial) at the exit which was greater than zero for all shear rates investigated. These extrapolated values of “exit pressure” were used to calculate values of the primary normal stress difference at the shear rates considered. The differences so calculated were found to correlate well with shear rate.