Stretch wrap - AbsoluteAstronomy.com

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

Shrink wrap

Shrink wrap, also shrinkwrap or shrink film, is a material made up of polymer plastic film. When heat is applied it shrinks tightly over whatever it is covering. Heat can be applied with a hand held heat gun or the product and film can pass through a heat tunnel on a conveyor.-Composition:The...

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

Ethylene

Ethylene is a gaseous organic compound with the formula . It is the simplest alkene . Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone...

with alpha-olefins, the most common of which are butene, hexene

Hexene

Hexene is a higher olefin, or alkene with a formula C6H12. The "Hex" is derived from the fact that there are 6 carbon atoms in the molecule, while the "ene" suffix denotes that two carbon atoms are connected via a double bond. There are several isomers of hexene, depending on the position of the...

and octene

Octene

Octene is an alkene with the formula . Several isomers of octene are known, depending on the position of the double bond and the branching of the carbon chain....

. 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

Puncture resistance

Puncture resistance denotes the relative ability of a material to inhibit the progression of a tear once it has been pierced by a cut or a nick. Tests devised to measure puncture resistance are generally application-specific, covering items such as roofing and packaging materials, protective...

. Other types of polyethylene

Polyethylene

Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...

and PVC

Polyvinyl chloride

Polyvinyl chloride, commonly abbreviated PVC, is a thermoplastic polymer. It is a vinyl polymer constructed of repeating vinyl groups having one hydrogen replaced by chloride. Polyvinyl chloride is the third most widely produced plastic, after polyethylene and polypropylene. PVC is widely used in...

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.These machines offers safety for the products.

There are two methods of producing stretch wrap.
1) Blown: the resin is melted and blown out, it is air-cooled. This is a slower process but provides for higher quality in all the areas listed below. The cost of production is also higher due to the quantity that can be produced per hour.
2) Cast: the film is passed over cooling rollers. This makes the cooling process quick. The quality is not as good as blown but more can be produced in an hour lower costs.

Other properties such as break strength, cling, clarity, tear resistance, static discharge, etc. are also important.

Functions

In pallet

Pallet

A pallet , sometimes called a skid, is a flat transport structure that supports goods in a stable fashion while being lifted by a forklift, pallet jack, front loader or other jacking device. A pallet is the structural foundation of a unit load which allows handling and storage efficiencies...

unitizing, stretch wrap can have several functions:

improved stability of products or packages, forming a unit load
Unit load
A unit load combines individual items or items in shipping containers into a single "unit" that can be moved easily with pallet jack or forklift truck...
more efficient handling and storage of unit loads
some degree of dust and moisture protection
some degree of tamper resistance
Tamper resistance
Tamper resistance is resistance to tampering by either the normal users of a product, package, or system or others with physical access to it. There are many reasons for employing tamper resistance....

and resistance to package pilferage
Package pilferage
Pilferage is the theft of part of the contents of a package. It may also include theft of the contents but leaving the package, perhaps resealed with bogus contents. Small packages can be pilfered from a larger package such as a shipping container...

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

Categories and sub-categories of stretch wrappers:

Manual (or Hand) Wrappers:

Extended Core
Extended Core Stretch Wrapper
Extended core stretch wrappers are rolls of stretch film which have their internal core extended beyond their film roll creating a handle by which film can be wrapped. Extended core wrapping is the lowest initial investment stretch wrapping system as no machinery is purchased. This system...

: An extension of the film's core serves as a handle for wrapping; this type of wrapper offers little stretch control and is hard on hands.
Mechanical Brake
Mechanical Brake Stretch Wrapper
Mechanical brake stretch wrappers are manual stretch wrapping systems which consist of a simple structure supporting a roll of film to be stretched and a mechanical brake which acts on the film roll, creating resistance to turning and stretching the film as it is fed out.The amount of braking is...

: A simple structure supports a film roll and a mechanical brake system provides resistance creating stretch of the film.
Pole Wrappers: Similar to the Mechanical Brake system, but the roll and brake are at the end of an extended pole, creating an ergonomic design which eliminates the need to bend to wrap the bottoms of loads and strain to reach the tops of loads.

Semi-Automatic Wrappers:

Turntable Wrappers
Turntable Stretch Wrapper
Turntable stretch wrappers are a type of semi-automatic stretch wrapping system. A load is placed on a turntable, which rotates relative to the film roll, which is housed in a carriage attached to a vertical "mast" on which it may move up and down...

: The load to be wrapped sits on a turntable which spins the load relative to the film roll, which is housed in a carriage which can move up and down a fixed "mast". Stretch is achieved by rotating the load at a faster rate than the film is fed.
Orbital Wrappers
Orbital Stretch Wrapping
Orbital stretch wrapping is a means of applying stretch film to a load consisting of a roll of stretch wrap supported on a vertical rotating ring and a means of passing a load through the ring's eye horizontally....

: The film is housed in a carriage on a vertical ring, the load is fed horizontally through the eye of the rotating ring, applying film to the load. A variation of an orbital stretch wrapper is a horizontal ring system, in which the load remains still while a horizontal ring is rotated around the load and moves up and down vertically relative to the load, similar to a rotary arm stretch wrapper.
Rotary Arm Wrappers
Rotary Arm Stretch Wrapper
Rotary-arm stretch wrappers are systems to deliver stretched film onto a load by means of supporting a film roll within a carriage attached to an arm, rotating around a stationary load. The film carriage is able to move along the arm vertically, moving the stretch wrap up and down relative to the...

: In this system, the load remains still while a rotating arm turns around it wrapping the load. This system is used for light loads or for speeds which would otherwise cause the load to topple due to high rotation speeds.

Automatic Wrappers:

Automatic wrappers are generally a variant of a semi-automatic system. Automatic wrappers include a conveyor system to automatically load the wrapping machine and automatic systems to apply, seal, and cut the film.

Packaging and labeling
Palletizer
Palletizer
right|thumb|250px|Palletizer using roboticsA palletizer or palletiser is a machine which provides automatic means for stacking cases of goods or products on to a pallet. The first palletizer was designed, built, and installed in 1948 by a company formerly known as Lamson Corp. There are specific...
Plastic recycling
Plastic recycling
Plastic recycling is the process of recovering scrap or waste plastics and reprocessing the material into useful products, sometimes completely different in form from their original state. For instance, this could mean melting down soft drink bottles and then casting them as plastic chairs and tables...
Plastic wrap
Plastic wrap
Plastic wrap, cling film , cling wrap or food wrap, is a thin plastic film typically used for sealing food items in containers to keep them fresh over a longer period of time...
Slip Sheet
Slip Sheet
Slip sheets are thin pallet-sized sheets made of plastic, heavy laminated kraft paperboard, or corrugated fiberboard used in commercial shipping. Often, these replace the use of traditional wooden pallets...

Materials

Functions

Application

See also

Further reading