What are the Differences Between Cast Stretch Wrap and Blown 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.
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.
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. Our blown hand stretch film is a common example of this type of film. It has a much higher rating than our cast hand film for holding power and puncture resistance.
7 Point Comparison Chart
|
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 |