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 wrap is 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.

Types of stretch film include bundling stretch film, hand stretch film, extended core stretch film, machine stretch film and static dissipative film.

 

Materials

The most common stretch wrap material is linear low-density polyethylene or LLDPE, which is produced by copolymerization of ethylene with alpha-olefins, the most common of which are butene, hexene and octene. The use of higher alpha-olefins (hexene or octene) gives rise to enhanced stretch film characteristics, particularly in respect of elongation at break and puncture resistance. Other types of polyethylene and PVC can 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, static discharge, etc. are also important.

 

Functions

In pallet unitizing, stretch wrap can have several functions:

• improved stability of products or packages, forming a unit load
• more efficient handling and storage of unit loads
• some degree of dust and moisture protection
• some degree of tamper resistance and resistance to package pilferage

Making sure cartons stay on the pallet is an important consideration in warehouse distribution, especially as the demands for increased throughput continues to rise. Stretch wrapping is the most cost-effective way to keep loads secured on a pallet.

 

Application

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.