Cast VS Blown Stretch Wraps and Films

Learn the differences in Blown and Cast Stretch Films at PTIPackaging.com!
If you have more questions on blown stretch film or cast stretch films, please call us at 1-800-472-0067!

What are the differences between blown stretch wrap and cast stretch wrap?
The primary difference between these two types of Stretch Wrap Film is the process in which they are created and manufactured. These differences also make a big impact on the usability and price of the film.

Creation and Manufacturing Process

Creation of Blown Stretch Wrap
Beads of resin are fed through a heated machine that has a circular die. The heated resin is forced through the die and then blown out vertically into a bubble. As this formed bubble finishes the process of being transformed into rolls of stretch film, it is cooled by the surrounding air. This type of film generally costs more to make because the output per hour is less than with cast films. Blown stretch wrap such as our Stretch Film is a common example of this type of film.

Creation of Cast Stretch Wrap
The cast process beings the same as blown, with beads of resin being fed into a heated barrel and being forced through a narrow slotted die. This 'sheet' of film the die produced is then fed along a rolling path that has been cooled, which solidifies the film. It is then brought through the final stages of production and made into large rolls. This method is much faster than the blown extrusion method and also costs less, as more can be produced per man hour. Machine Stretch Wrap is the most common type of film produced by this method.

7 Points of Comparison

Blown Stretch Film

Cast Stretch Film

1). Load Retention:

More holding power, won't re-stretch once applied

Stretches easily, even after applied to pallet which can cause shifting

2). Film Memory:

Higher ability to shrink back to original size after stretch

Minimal ability to go back to original state after stretching

3). Film Yield:

Stretches much farther to cover more pallets with less film

Additional stretching can be obtained easier through lower micron blown films (Conversion Chart)

4). Puncture Resistance:

Manufacturing process allows greater resistance to breaking

Standard tearing can occur when stressed too much

5). Cling of the Film:

1 sided cling, great for higher load retention

Naturally clingy on both sides, can make pallets stick together

6). Visual Clarity:

Not crystal clear, can make reading and scanning harder, but has a lower gloss reducing reflections

Perfectly clear, makes reading and scanning in warehouse light easy, but a higher gloss makes reflections annoying.

7). Noise on unwind:

Loud when releasing from the roll

Very quiet when unwound from the stretch roll