article

Abstract

The extensional viscosity of some flexible chain polymers and a thermotropic liquid crystalline polymer was measured in uniaxial extensional flow at constant extension rate and compared with the values calculated from pressure measurements in axisymmetric entry flow. The comparison showed that, except for the LCP, the values of the extensional viscosity calculated by the latter method correspond to the ones measured in the uniaxial extension averaged over extensional strain equal to what is accumulated on the fluid as it flows from the barrel into the capillary in the entry flow.

Rheologica Acta, 37, 430-437, 1998

The relevance of entry flow measurements for the estimation of extensional viscosity of polymer melts.