Elongational Flow of Polymer Melt

Abstract

An experimental study of elongational flow behavior in melt spinning process is reported. In general, elongation al viscosity of running filament is a function of shear history, elongational strain rate, and time, as well as temperature. Viscosity in the vicinity of the spinneret along the spinline is influenced by the shear flow in the spinneret, and is different from that of the elongational flow. The elongational viscosity increases with decreasing temperature and still increases as time passes in the region far from the spinneret, where elongational flow is fully developed. The increase of the elongational viscosity with time in melt spinning corresponds well to the results of constant-strain-rate experiments. The elongational viscosity in constant-strain-rate experiments rapidly increases with time at a certain critical strain. The rapid increase behavior does not depend on strain rate, temperature, and average molecular weight, but depends on molecular weight distribution and chain branching. These elongational flow properties have been discussed in terms of rheological models