Jul. 19, 2021
In its simplest form, a temporary surface protection film is a thickness of plastic coated with a certain thickness of a specialized pressure-sensitive adhesive (PSA). A keyword to describe protective film adhesives is "temporary". By design, temporary surface protection films do not remain on the surface indefinitely. So what are the different types of protective films and what are the differences between them?
LDPE (Low-Density Polyethylene).
Co-Ex (co-extruded LDPE), and
PVC (polyvinyl chloride).
LDPE or low-density polyethylene is the most common type of protective film. It is made from polyethylene, which is the most common type of plastic. As you might guess from the name, there is also a high-density version of polyethylene (HDPE), which is heavier, less flexible, and less elastic, and therefore less useful in making protective films. LDPE films come in a variety of types and can be used in many different applications.
COEX or Co-Ex LDPE stands for Co-Extruded Low-Density Polyethylene. Co-extrusion refers to the simultaneous manufacture of two or more layers of plastic and together to form a single film. For example, a common co-ex combines a layer of black plastic with a top layer of white plastic. This allows you to take advantage of the different properties of each layer, such as combining UV-reflecting (white) with UV-absorbing (black) to provide better overall UV protection.
Protective Film for Deep Drawing
PVC, or polyvinyl chloride, is probably the best-known type of plastic. PVC film is very flexible and has a smooth surface, which makes it ideal for many metal forming applications, among other uses.
PP, or polypropylene, is a plastic that can be used in high-temperature applications. It is dimensionally stable, which means it can retain its shape and size and is not as stretchy as PVC film.
PO or polyolefin is a plastic film used for some painted metal surfaces and acrylic glass applications.
Paper can also be used as a surface protection film. Paper films are dimensionally stable and can absorb some impact.
Film thickness is often described as the total thickness of the plastic and adhesive. In the United States, the film is measured in thousands of inches or mils. (This is not the same as millimeters.) Typical film thicknesses range from 1 mil to 6 mils, sometimes higher. The thicker the film, the more resistant it is to abrasion, scratching, etc. Thicker films tend to be harder and more difficult to apply to contoured surfaces.
The type of adhesive is also an important consideration. Textured surfaces often require thicker and softer adhesives. If the adhesive only touches the "peaks" of the surface, it may touch less than 5% of the total surface area and tend to peel off the surface. Adhesives for textured surfaces also tend to have higher tack values.
Adhesion or adhesive tack is measured in ounces per inch. For best performance, it is best to use a minimum tack value that adheres well enough to hold the film to the surface for its life. Using a higher level of adhesion than desired increases the risk that the film will be difficult to remove or leave adhesive residue. For example, a protective film used to protect cell phone LCD screens has a tackiness of about 1 ounce per inch. Films used to protect carpets have a tackiness of 25 oz/inch or higher. Using carpet film on an LCD display may pull the display apart when the film is removed.
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