Effects of Extrusion Conditions on Melt Viscoelasticity during Capillary Flow of Low-Density Polyethylene

Abstract

The melt viscoelastic properties of a low-density polyethylene (LDPE) are measured, at temperatures varying from 140°C to 170°C and in a wide range of extrusion rates by means of a capillary rheometer, to identify the influence of extrusion conditions (such as temperature, die diameter, and flow rate) on the melt viscoelastic behavior. The results show that the entry pressure drop (▵Pen) and the melt extension stress are a quadric function of extrusion rate (V), and it decreases with an increase in die diameter (d). Similarly, the die-swell ratio (B) increases nonlinearly with increasing V and shear stress at the channel wall. The dependence of B on temperature corresponds approximately with the Arrhenius expression. Under these experimental conditions, the ▵Pen and B increase roughly as an exponential function with an increase in the channel contraction ratio.