Influence of Resin Molecular Weight on the Moisture Permeability of HDPE Blown Films

Abstract

A set of high density polyethylene (HDPE) blown films was produced from five resins of varying molecular weight under identical processing conditions. Film morphology was characterized in terms of crystalline content using refractometry as well as quantification of crystalline phase orientation through the application of Fourier transform infrared (FTIR) linear dichroism. Additional insight into film structure was gained through the use of scanning electron microscopy (SEM). Water vapor transmission rate (WVTR) was observed to increase with resin molecular weight. The enhanced permeability of the higher molecular weight films was associated with slightly lower crystalline content and greater crystalline orientation relative to the lower molecular weight films. Due to the small differences in morphology and permeation behavior noted, the effect of orientation on WVTR performance between the films studied was only significant for the most highly oriented film.