LLDPE rheology and blown film fabrication

Abstract

AbstractExtrudate irregularities, or “melt fracture,” with narrow MWD LLDPE resins occur at low deformation rates, and represent a severe rate limiting factor in commercial blown film fabrication with narrow die gaps. Extensive capillary rheometer measurements for several polymers, and blown film fabrication studies for LLDPE, seem to support an earlier finding that slip in the die land region invariably accompanies the observed extrudate irregularities. Lack of strong chemical forces for adequate adhesion at the polymer/metal interface in the die land region appears to be primarily responsible for the initiation of slip. Improvements in adhesion, by proper choice of the materials of construction and/or adhesion promoters in the resin, virtually eliminate the rate limiting effects of melt fracture in commercial blown film processing, and provide substantial improvements in critical end‐use properties, with LLDPE.