Premium
Studies on blown film extrusion. II. Analysis of the deformation and heat transfer processes
Author(s) -
Han Chang Dae,
Park Jong Yoo
Publication year - 1975
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1975.070191213
Subject(s) - extrusion , materials science , mechanics , bubble , isothermal process , heat transfer , rheology , deformation (meteorology) , work (physics) , thermodynamics , composite material , physics
Having investigated the elongational flow behavior of polymer melts (part I of this series), we have carried out both theoretical and experimental studies in order to better understand the deformation and heat transfer processes involved in blown film extrusion. For the experimental study, nonisothermal experiments were carried out, using high‐density and low‐density polyethylenes. Measurements were taken of the axial tension, bubble diameter, and film thickness at a series of extrusion conditions (i.e., flow rate, pressure difference across the film, and take‐up speed). For the theoretical study, an analysis was carried out to simulate the blown‐film extrusion process, by setting up the force‐ and energy‐balance equations on the blown bubble moving upward. The approach taken in the theoretical study may be considered as an extension of the earlier work by Pearson and Petrie who considered the isothermal operation of Newtonian fluids. In the present study, However, we have considered the nonisothermal operation of power law fluids, whose rheological parameters were determined by an independent experimental study an described in part I of this series. Four highly nonlinear differential equations were solved numerically with the aid of the CDC 360 digital computer, using the fourth‐order Runge‐Kutta method. The mathematical model predicts the bubble shape, temperature profile, and film thickness as a function of the distance along the machine axis. Comparison is made of the experimentally observed bubble shapes with the theoretically predicted ones, showing a reasonable agreement.