- Stretch wrap
Stretch wrap or stretch film is a highly stretchable plastic film that is wrapped around items. The elastic recovery keeps the items tightly bound. In contrast,
shrink wrapis applied loosely around an item and shrinks tightly with heat.
It is frequently used to unitize pallet loads but also may be used for bundling smaller items.
The most common stretch wrap material is
linear low density polyethyleneor LLDPE but other types of polyethyleneand PVCcan also be used. Many films have about 500% stretch at break but are only stretched to about 100 – 300% in use. Once stretched, the elastic recovery is used to keep the load tight.
Other properties such as break strength, cling, clarity, tear resistance, puncture resistance, static discharge, etc. are also important.
In pallet unitizing, stretch wrap can have several functions:
* improved stability of products or packages, forming a
* more efficient handling and storage of unit loads
* some degree of dust and moisture protection
* some degree of
tamper resistanceand resistance to package pilferage
Stretch wrap can be applied manually with small rolls (perhaps 5 inch wide) of film. Dispensers are also available for larger rolls (perhaps 12 – 15 inch wide).
Machinery is available to automate the operation. This controls the amount of material used, controls the stretch, and controls the application pattern.
It is important not to apply too much tension or too many layers: the stress can damage the vertical edges of the boxes and significantly reduce stacking strength.
ASTMD4649 Guide for Selection and Use of Stretch Wrap Films
* Brody, A. L., and Marsh, K, S., "Encyclopedia of Packaging Technology", John Wiley & Sons, 1997, ISBN 0-471-06397-5
* M.Hindreth, "Maximizing your Stretch Film Operation", 2006, ISTA, Pre Shipment Testing, [http://www.ista.org/Membership/PST2007Issue1.pdf]
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