This article summarizes how the differences between cast and blown film processes translate into film attributes. These are general rules of thumb that will largely hold for a type of polymer
There are principally two major impacts on film characteristics of the differences between the cast and blown processes. The first is quench rate, with is much higher for cast than blown film; the higher quench rate for cast film results in lower crystallinity in semi-crystalline polymers, like polyethylenes, polypropylenes, polyamides, PET, and EVOH, all key packaging film components.
Quench rate impact on cast and blown films
The second major process impact is the creation of some melt orientation in the MD only for cast and in both MD and CD for blown. The results of this is a more directional film from cast and a more balanced film for blown. The relative advantages and disadvantages of blown vs. cast resulting strictly from melt orientation have a few more subtleties than the strictly quench rate effects, for some applications.
Melt orientation impact on cast and blown films
It must be noted that the quench rate and melt orientation impacts and differences between the two processes do not occur in isolation, and all the characteristics of the end use need to be considered in determining which film is better suited.
