To Shrink or To Stretch

Find out the differences between shrink and stretch wrap.
By Mel Parnes President. Ciratec Corp.

Shrink wrap is a packaging technique where the plastic film is wrapped around a product and heat sealed to form a loose envelope. It is then heated all over, causing the wrap to shrink tightly around the product. On the other hand, stretch wrap is an elastic film that is mechanically stretch around the product like a wide rubber band. It is not heat sealed but relies on a self adherence. It is applied in plys, overlapped it self.

Differences?

To visualise the difference, a toy or a box of software might be shrink packaged. You can see the line of the heat seal that was made before the shrinking took place, but the print on the product is clearly visible through the film. The film is clear and relatively slippery.

On the other hand, a pallet or skid of boxes is stretch wrapped. A stack of shrink wrapped boxes or software might be stretch wrapped. The film used is a hot like, if not identical to, the household wrap which we use to call "saran wrap" (it is usually not saran anymore). It is clear but many wrinkkes occur where the film overlaps it self, making it less aesthetically appearing.
stretch wrap is therefore more of a shipping tool, while shrink wrap is more to keep a product clean until after it is in the hand of the customer.

Functions

There are a lot of overlap in the functions of the two products. Shrink wrap is also used to package cases of dog-food and other products shipped in bulk where the package is opened at the market and it is not seen by the customer. Stretch wrap, on the other hand used more and more to unitise small bundles for shipping. Shrink wrap, is an older technique preceding stretch wrap by more than 10 years. Before stretch wrap was used, shrink wrap performed many of its functions. It was soon discovered that stretch wrap was better than shrink wrap for heavy duty industrial packaging, since it was no less effective and cheaper and easier to use.

Shrink wrap is energy intensive since heat must be produced to shrink the film. The shrink machinery usually requires more maintenance since heat sealing of the film is necessary. Stretch wrap film is designed to adhere it self (no adhesive is used though). The film has a high coefficient of friction. It can prevent a package from sliding when a stack of product is handled.
The prevention of sliding may not be an asset when the high triction creates handling difficulties for people, or sliding difficulties for certain types of machine handling.

Source:
www.apfoodonline.com