Film Blowing of a Narrow Molecular Weight Polyethylene

Abstract

Blown film properties have been evaluated for four high density polyethylene homopolymers while varying stalk height in the blown film process. Of the four homopolymers, three have narrow molecular weight distributions (MWD) and differ in their melt indices; the fourth has a broad MWD. Narrow MWD film properties have been significantly affected by increasing the stalk height from zero die diameters to several die diameters. Water vapor transmission rates decrease by 50-70% and the films become hazy and dull. In contrast, stalk height’s influence on broad MWD film properties is slight. The narrow MWD resins are consistently clearer and glossier than the broad MWD resin.