The end pressure losses during short die extrusion of LLDPE melt

The end pressure losses and the factors affecting them during short die ext rusion of a linear low density polyethylene (LLDPE) melt have been investig ated under the experimental conditions of temperatures from 230 to 260 degr ees C and apparent sheer rates of 12 to 120 s(-1), by employing a capillary rheometer and a set of dies with different diameter and length. The result s show that the entry pressure loss, Delta P-en, increases nonlinearly with increasing shear rate, and is an index function of the wall shear stress; the dependence of Delta P-en on temperature accords with a formula such as the Arrhenius equation; Delta P-en decreases with increasing die diameter; Delta P-en is more than 80% of the end pressure losses. (C) 2000 Elsevier S cience Ltd. All rights reserved.