Fundamentals of Melt Fracture Elimination Using Fluoropolymer Process Aids, 2002 PLACE Conference Proceedings

Fluoropolymer process aids are widely used in polyolefin blown films to eliminate melt fracture. These process aids function by depositing a thin fluoropolymer layer on internal die surfaces, and promoting slip at the fluoropolymer – polyethylene interface. Although the extrusion characteristics of polyolefins have been studied extensively under steady-state conditions corresponding to either zero fluoropolymer or a complete fluoropolymer coating on the die, factors controlling the rate of fluoropolymer deposition have received little attention. The present work describes how the morphology of fluoropolymer – polyethylene blends can be controlled to increase fluoropolymer deposition rate by using a new, rheology-modified fluoropolymer in combination with an interfacial agent. The resulting process aids not only decrease the fluoropolymer requirement needed to quickly eliminate melt fracture, they exhibit less of the variability commonly experienced with conventional process aids when subjected to changes in resin/additive systems, compounding equipment, dosing level, or film extrusion techniques.