Shrink Wrap and Stretch Films Information
Shrink wrap and stretch films hold items together in packaging and palleting applications. Shrink wrap and stretch films are lightweight but puncture and tear resistant, making them a cost effective alternative to box or container packaging. They also secure items stacked on pallets for storage or shipping. Shrink wrap and stretch films used on pallets much be of a particular gauge, or pallet weight, to support the load.
Shrink wrap is typically a clear plastic or polymer-based film that shrinks when heated to conform to the shape of the object it is wrapped around. Shrink wrap can form a very tight, tamper-evident seal to protect the products from insects or other pests, moisture, dust or other contaminants, and discourage theft. Shrink wrap is commonly used as food bags and in other perishable applications. Shrink wrap is available in a variety of widths, designs, and film gauge, depending on the application.
Stretch films are designed to cling tightly to objects and provide a secure overwrap to protect them from shifting during transport. Stretch films can be used to wrap pallets by machine or by hand, and include clear plastic films or printed or colored stretch wrap.
Stretch wrap is made of polyethylene plastic and unlike shrink wrap, which responds to heat to shrink and secure the load, stretch wrap has an elastic memory and functions much like a stretched rubber band.
Stretch film production process. Video credit: King Mak / CC BY-SA 4.0
Material is important for these films because it affects the elasticity for stretch wrap films and how much a film will shrink. The material will also effect other properties such as how well you can see through the film, whether the film is stable in UV light (approved for outdoor use), and electrical properties such as conductivity and dielectric specifications.
Other material properties to consider include thickness, moisture resistance, and chemical resistance. Chemical resistance is especially important if the film will come into contact with food or if the film will hold corrosive products on the pallet.
These plastics can be used as agricultural films to reduce weed growth or protect seedlings, provide a vapor or air barrier in construction applications, and are used as lightweight can liners and trash bags for all waste management applications.
Shrink wrap and stretch films must adhere to certain standards to ensure proper design and functionality. Standards such as ASTM D4649 are used for selection and use of stretch wrap films. ASTM D5416 and BS 2782-6 discuss the methods of testing abrasion resistance and shrinkage on heating respectively.