Often confused with shrink-wrap, stretch film, or stretch wrap is a high elongation, polyethylene based film made from linear low-density polyethylene resins. Due to its elastic recovery capabilities, excellent adhesion and puncture resistance, stretch film is commonly used in packaging industries to unitize small individual items into large unit loads (pallets) as well as protect products during storage and shipment.
Depending on your packaging preferences, stretch films are available in varying widths, thickness, and type. For example, a stretch film with a thickness of 17 microns is convenient for stretch wrapping ordinary loads. Conversely, a stretch film with a thickness of 20 or 23 microns would be more suitable for stretch wrapping heavy, unstable loads, with sharp edges.
Types of Stretch Film
There are numerous brands and configurations of stretch film in the market today. Although the categories are many, the main variation is dependent on the gauge, manufacturing, and how the film is applied. Here are the two primary types of stretch film.
Hand Stretch Film
Also referred to as manual pallet wrap, hand stretch film is specifically designed to be applied manually whereby an operator attaches the film to the load and then proceeds to unwind the film as he moves around the load. This process is mostly used in lower packaging operations. However, the efficiency of hand stretch wrap should frequently be re-evaluated against the possible benefits of advancing to machine applied films.
Machine Stretch Film
Machine stretch film is utilized in combination with a stretch wrapping machine that applies the film to the load based on the parameters set by the operator. It provides numerous advantages over the manual pallet wrap including consistent professional packaging, faster packaging, stretch film economy due to reduced film waste, and safer film application.
Common Stretch Films Include:
Commonly known as cast film, this film is manufactured using the cast extrusion process. Cast film offers excellent optics, increased tear and puncture resistance, superior cling, and more consistent film thickness. Cast film is superior to blown film in tear strength in the machine or transverse direction, which aids in the prevention of tear propagation.
Blown Stretch Film
Typically, blown film is a higher quality designed for high load and stretch capacity. Common characteristics include cloudy optics, excellent puncture resistance, and high force on the load.
Terms you may hear of
Cling allows the film to stick to self but not to the product. Some films have one- sided cling or two-sided cling.
This is the speed at which stretch film applied to the load by a stretch film machine.
Force to Load
Usually measured in pounds, film force is the amount of tension applied to the film as the film is applied to the load.
This is the amount of stress stretch film can withstand without permanently undergoing plastic deformation. Once stress is removed, the material will attempt to return to original shape.
The process of feeding, melting and pumping a material such that a desired shape or configuration can be created. It is a continuous process and utilizes a device similar to a "meat grinder."
A measure of thickness, sometimes used as a synonym for film thickness or film caliper, and expressed in other units such as microns.
A metric measurement of thickness, also known as a micrometer.
A conformation irregularity found in rolls of material. A thick area in a film will produce a raised or elevated ring in a finished roll or product.
Prestretch (referring to stretch film wrappers)
The extent to which a film is increased in machine direction length within the prestretch head. Ideally, in the absence of film slippage on the prestretch rollers, or other problems, it is determined by the relative surface speeds/gearing of the prestretch rollers.
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