Entry pressure correlations in capillary flow

Abstract

The entry pressure in capillary rheometry is determined by using the Bagley correction method to accurately determine the viscosity of polymers at high shear rates. This method requires the use of at least three capillary dies having the same diameter and different lengths. In this paper, the entry pressure of over 40 sets of experimental data for different polymers is correlated as a function of wall shear stress for two different classes of polymers, namely, linear and branched. The derived correlations can directly be applied to correct the raw capillary data from a single capillary die, thus minimizing the experimental error, effort, and time.