By using the theoretical equations on tubular film extrusion, we presented a scale-up rule for setting the conditions which make the stretch stress constant both in MD (machine direction) and in TD (transverse direction). The rule originated from a concept of the maximum stretch stresses at the frost-line level. The rule was applied to HDPE tubular film extrusion under the different film thickness and width. The melt behavior in tubular process, the orientation factors of films, and the physical properties of films were independent on film width and thickness under the scale-up conditions. That is, the scale-up rule worked well.
We are able to predict the film processability and film physical properties for the large scale tubular film process, once the tubular film extrusion is carried out by using the small scale machine and a small amount of resin.