The Use of Deformation Rates in the Scale-Up of Polyethylene Blown Film Extrusion

Abstract

It is often desirable to scale up a process from a lab scale system, where most research occurs, to a large scale industrial system with minimal ex penses of time and money. This work will show that under appropriate process ing conditions, blown films can be produced under similar strains that yield comparable crystalline morphologies and therefore equivalent mechanical properties. A tracer technique was used to determine deformation in the formation of blown films and applied to both an industrial blown film line and a smaller lab scale analog. Using computer-enhanced image analysis, strain and strain rate data were acquired from the tracer technique. Large and small scale data were compared for similarities in shape and magnitude of respective data plots. Mechanical testing of the films showed that uniaxial and biaxial toughnesses and modulus were similar for paired runs based on a scale-up factor of 1/3 based on output per die circumference. Wide angle X-ray analysis showed struc tural or morphological similarities between films produced under parallel con ditions. The data presented shows that a successful scale-up of polyethylene blown film extrusion was completed using appropriately matched processing condi tions.