Scale-Up and Processing-Structure-Property Analysis of the Blown Film Process

Abstract

Blown film processing is an important but very complex process. A blown film scale-up strategy proposed earlier by T. Kanai et al. was revisited in this work. The blown film process was scaled up very successfully using that strategy. Furthermore, the strategy is shown by this work to be independent of resin or polymer type, die size, die gap and extrusion differences such as die and extruder shear rates provided that all of the other criteria set by the strategy are fulfilled. Using bubble kinematics it was found that the principal strain rate profiles in the machine and transverse directions and the cooling rate pro files were largely similar under the scale-up conditions. High resolution scan ning electron micrographs showed that the stacked lamellar morphology that is developed under scale-up conditions is also largely similar-resulting in equivalent film properties. Lastly, some trends between the strain rates, mor phology and film properties are suggested.