Some studies on the swelling behavior of polyethylene

Abstract

Abstract When polymers are extruded from a capillary, the amount of extrudate swelling is generally found to be a function of shear rate and capillary dimensions. Experiments with polyethylene now show that when shear rate is replaced by an average transit time in the capillary, postextrusion swell becomes a function of transit time only. Plots of swell versus transit time are independent of the applied stress and reduce to a single line for capillaries of different dimensions. The swell was found to be dependent upon the average molecular weight and the molecular weight distribution. Little correlation, however, was found with the amount of high molecular weight fractions.