A release liner or ''release paper'' is a paper or plastic-based film sheet (usually applied during the manufacturing process) used to prevent a sticky surface from prematurely adhering. It is

coated A coating is a covering that is applied to the surface of an object, usually referred to as the substrate. The purpose of applying the coating may be decorative, functional, or both. Coatings may be applied as liquids, gases or solids e.g. Powder ...

on one or both sides with a

release agent A release agent (also mold release agent, release coating, or mold release coating) is a chemical used to prevent other materials from bonding to surfaces. It can provide a solution in processes involving mold release, die-cast release, plastic r ...

, which provides a release effect against any type of a sticky material such as an adhesive or a

mastic Mastic may refer to: Adhesives and pastes *Mastic (plant resin) *Mastic asphalt, or asphalt, is a sticky, black and highly viscous liquid * Mastic cold porcelain, or salt ceramic, is a traditional salt-based modeling clay. *Mastic, high-grade con ...

. Release liners are available in different colors, with or without printing under the low surface energy coating or on the backside of the liner. ''Release'' is separation of the liner from a sticky material; ''liner'' is the carrier for the release agent.

Industry segmentation

Globally there are between 400 and 500 companies involved in making or dealing with release liner products on an industrial scale. In general there are two types of companies which are manufacturing release liner.

Liner producer

Commercial coating companies deal with a lot of different end uses of this industry. They provide unique solutions to their customers, based on a wide variety of substrates and an endless combination of release agents with specialized properties. Commercial coaters usually do not make finished products, just the release liner itself and then their customers will coat a sticky material on this liner and then apply the end product to it.

In-house producer

An in-house producer makes the release liner and uses it internally to manufacture the final product. In-house producers are typically focused on a very narrow range of products e.g. labels or tapes. They use a limited amount of substrates and release materials, which are specialized for their end applications.

Liner materials

As ''liner'' material, the industry is using a wide variety of so-called substrates, which are the carrier materials of the release agent and which is needed to transport a sticky material from the manufacturer to an industrial or private end user. Typical liner materials are:

Paper

# SCK - Super calendered Kraft paper, typically used for labels in the USA # Glassine - Is also a SCK paper but typically with a

polyvinyl alcohol Poly(vinyl alcohol) (PVOH, PVA, or PVAl) is a water-soluble synthetic polymer. It has the idealized formula H2CH(OH)sub>''n''. It is used in papermaking, textile warp sizing, as a thickener and emulsion stabilizer in polyvinyl acetate (PVAc) ...

(PVOH) top coat, typically used for labels in Europe # CCK - Clay coated Kraft paper or also just called coated paper # MFK - Machine finished Kraft paper, which is the paper as it comes from a standard paper machine # MG - Machine glazed paper which is a paper which has been glazed, e.g. on a Yankee cylinder of a paper machine

Plastic film

# BO-PET: a

PET film (biaxially oriented) BoPET (biaxially-oriented polyethylene terephthalate) is a polyester film made from stretched polyethylene terephthalate (PET) and is used for its high tensile strength, chemical and dimensional stability, transparency, reflectivity, gas and ar ...

is a very high temperature resistant and tough film liner # BOPP: a biaxially oriented

polypropylene Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene. Polypropylene belongs to the group of polyolefins a ...

(PP) film # Other polyolefins: typically made out of

high density polyethylene High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a thermoplastic polymer produced from the monomer ethylene. It is sometimes called "alkathene" or "polythene" when used for HDPE pipes. With a high strength-to-density ratio, ...

(HDPE),

low density polyethylene Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. It was the first grade of polyethylene, produced in 1933 by Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerization. Its ...

(LDPE), PP plastic resins Plastic films in general are made out of plastic resins by a

plastics extrusion Plastics extrusion is a high-volume manufacturing process in which raw plastic is melted and formed into a continuous profile. Extrusion produces items such as pipe/tubing, weatherstripping, fencing, deck railings, window frames, plastic fi ...

process and can be made out of one single type of plastic material, a blend of different plastic materials or multilayered coextrusions. Providing them with unique and adjusted features for the application that they are targeted for.

Others

* Poly coated Kraft papers, which are typically MFK papers which have a polyolefin coating on one or both sides, to make them very smooth, moisture resistant and dimensionally stable. * Poly coated BO-PET film, which is a BO-PET film that has been coated on both sides with a polyolefin material. This way the tough and dimensionally stable PET film is combined with cheap polyolefin resin which makes the film a better carrier web for specialty applications.

Release agents

Commonly used release agents for release liner can be crosslinkable silicone, other coatings, and materials that have a low surface energy.

Applications

There are probably hundreds of different applications, where release liner materials are being used. Such as * Pressure-sensitive

label A label (as distinct from signage) is a piece of paper, plastic film, cloth, metal, or other material affixed to a container or product, on which is written or printed information or symbols about the product or item. Information printed ...

s *

Pressure-sensitive tape Pressure-sensitive tape, known also in various countries as PSA tape, adhesive tape, self-stick tape, sticky tape, Sellotape, or just tape, is an adhesive tape that will stick with application of pressure, without the need for a solvent (such a ...

Self-adhesive plastic sheet Self-adhesive plastic sheet, known in the United Kingdom as sticky-backed plastic, is wide plastic sheet or film with an adhesive layer on one side, used as a surface coating for decorative purposes. It is typically smooth and shiny, but can also c ...

* Embossed release paper known as casting paper is used in the manufacture of textured materials, including

bicast leather Bicast leather (also spelled as bi-cast leather or bycast leather) is a material made with a split leather backing covered with an embossed layer of polyurethane or vinyl. Bicast leather was originally made for the apparel industry for glossy sh ...

and

artificial leather Artificial leather, also called synthetic leather, is a material intended to substitute for leather in upholstery, clothing, footwear, and other uses where a leather-like finish is desired but the actual material is cost prohibitive or unsuitab ...

References

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