Stretch wraps or stretch films are highly expandable
In the shipping and packaging industry, stretch films are used throughout to consolidate loads of items for shipment.
Packaging companies most frequently use automated spiral turntable machines. As the pallet or crate rests on the rotating turntable, the stretch wrapping machine feeds film to the load as it moves up and down, creating a series of overlapped wraps up and down the sides of the wrapped item. For high-volume production, non-conveyor operations use dual turntable stretch wrappers. There are other types of stretch wrappers and stretch wrapping machines, which will be described in the latter part of this article.
The most common material used in stretch films is LLDPE or linear low-density polyethylene*, which has two methods of manufacturing: blown (air-cooled) and cast (the film is passed over cooling rollers). But what makes the material important is its resistance to tears and breakage, its cling factor, clarity, and static discharge that enables the product to perform its foremost packaging functions: 1. improve the stability of the package; 2. efficient handling and storage of the package; 3. protect it from dust and moisture; and 4. to avoid product tampering or pilferage.
Bundling-stretch films, hand-stretch films, extended core stretch films, machine-stretch films, and static-dissipative films are types of stretch wrappers used by packaging companies.
1. Bundling stretch films are used to bundle small, light-weight products for shipment. It is a quality, quiet cast film. More economical and faster to use than strapping or tape.
2. Hand-stretch films offers optimum load-holding force and unrivaled puncture resistance. This is a popular choice for wrapping most small to medium sized items.
3. Extended core stretch films has the same definition with bundling stretch films except that it has a built-in handle so each stretch wrap roll is ready to use of the box.
4. Machine-stretch films ideal for heavy and bulk loads. Machine-stretch films offer optimum load-holding force and unrivaled puncture resistance why it is ideal for wrapping heavy, bulk loads.
Take note that stretch wraps are offered in clear films, colored-tinted, opaque (normally in black color), and anti-static films (ideal for wrapping gadgets and accessories like computers and or its parts).
Packaging companies use different kinds of stretch wrapping tools. Aside from hand-held wrapping tools (e.g. dispensers and extended core) it is also classified with into semi-automatic and automatic wrappers.
Turntable Wrappers -- The item to be wrapped sits on a turntable that spins it relative to the film roll, which is housed in a carriage which can move up and down a fixed 'mast'.
Orbital Wrappers -- In this tool, the film is housed in a carriage on a vertical ring, the item is fed horizontally through the eye of the rotating ring, applying film to the item.
Horizontal Ring Wrapper -- In this tool, the item remains still while a horizontal ring rotates around the it and moves up and down vertically relative to the item.
Rotary Arm Wrappers -- In this tool, the item remains still while a rotating arm turns around it wrapping the item.
Automatic wrappers are generally a variant of a semi-automatic system. Automatic wrapping machines include a conveyor system to automatically load the wrapping machine, apply, seal, and cut the stretch film.
* Linear low density polyethylene's (LLDPE) short chain branching gives it higher tensile strength, puncture and anti-tear properties, making it particularly suitable for film applications. Globally, over 80% of LLDPE goes into the film sector such as food and non-food packaging, shrink/stretch film and non-packaging uses. http://www.icis.com/v2/chemicals/9076159/polyethylene-linear-low-density.html
Sources: 1.) Yam, K. L., 'Encyclopedia of Packaging Technology', John Wiley & Sons, 2009, ISBN 978-0-470-08704-6; 2.) http://www.hpcorporategroup.com/stretch-wrappers-for-special-packaging-needs.html.