sourcehttp://www.flexp.com/blog/packaging
time2016/09/29
Stretch film comes in varying gauges, colors and can be used in numerous applications. The main variable and starting point for stretch films is blown versus cast.
Blown stretch film, or blown stretch wrap as it's also known, is created by blowing heated resin out vertically into a bubble. The bubble is then transformed into rolls while it is cooled by the surrounding air. Cast stretch film, or cast stretch wrap as it's also known, is created by feeding a sheet of heated resin along a rolling path with chilled rollers. The cooling solidifies the film, and it is made into large rolls.
Blown film is tougher and has less of a chance to puncture than cast. This occurs due to the slower cooling process, which allows the molecules in blown film to spread out as opposed to aligning in long lines like in cast. Blown film also has a higher level of cling (think Reynolds Wrap) than cast, making it stick to itself easier.
Cast stretch wrap has a clear, glossy finish allowing RFID and other scanning technology to be used with it while blown is hazy and dull. Cast stretch film unwinds much quieter than blown. It is also easier to stretch and control the gauge with cast film.
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