Friday, March 16, 2012

The Differences between Stretch and Shrink Wrap

There are a lot of people out there who should know better, but either don’t know, or have only a hazy appreciation of the differences between stretch and shrink wrap. Yes, both are synthetic plastics derived from petrochemicals. Both are durable materials with monumentally slow decomposition rates, and both will soften and/or melt when exposed to temperatures of around 210 degrees F. Nevertheless, the means by which stretch wrap and shrink wrap are produced, as well as their practical industry applications, are completely different. 

Blown Hand Stretch Film

Stretch wrap is made from low-density polyethylene (“polyethylene” coming from the Greek root-words “poly,” meaning “many”; and “ethyl,” meaning “purer air”), a common variety of plastic that gets its famous elasticity from the chemical synthesis of ethylene with alpha-olefins. Once these two different types of molecules are blended together through copolymerization, they are either left to cool in the open air, or are passed over with cooling rollers. The end result is a plastic with a surface that can be stretched up to 500% of its original area before breakage. The fact that stretch wrap is both pliable and sturdy make it the perfect plastic wrap for industrial palletizing. Large, bulky shipments are much less likely to spill when covered in stretch wrap.

LTG ShrinkFilm
Unlike stretch wrap, shrink wrap is a polymer plastic intended for packaging individual items and products. A randomly arranged set of plastic molecules gets heated with either a heat gun or a heat tunnel, causing the molecules to expand into a neater, more uniform arrangement. Once this new arrangement of plastics cools off, the wrap then “shrinks” back down to its original, rough dimensions. The plastic can be shrunk to fit around a packaged item very tightly (as in a CD case), though it can also be shrunk to fit more loosely around a particular item if a certain amount of flexible capacity is required. A new automobile would be an example of a larger item where shrink wrap gets applied more loosely, allowing for easier shipping and handling.

At Stamar, we specialize in both types of plastics. We carry many different varieties of stretch film: blown machine stretch film (stretch film that’s been naturally air-cooled), cast machine stretch film (stretch film that’s been machine-cooled), and our patented Goodwrapper ®stretch film, which allows for reduced friction on the hands when being wrapped or unwrapped. As far as shrink films, we offer LTG shrink film (ideal for individual food packaging), polyolefin shrink film (good for containing industrial equipment), and PVC shrink film, which is designed to shrink faster around its product when time is of the essence.

And that’s a wrap on plastic for now. Either way, we’ve got you covered.

3 comments:

  1. Thanks for sharing this information with us. This topic helps in increase the knowledge about Stretch and Shrink Wrap.

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  2. I recently found many useful information in your website especially this blog page. Among the lots of comments on your articles. Thanks for sharing.
    stretch film

    ReplyDelete