Of course, as a converter of flexible materials we love to talk about pressure sensitive adhesives (PSA). However the unsung hero of the adhesive world may be the release liner (often called “carrier” or “backing”). This is the product — typically a coated paper or film — that carries the sticky material and serves as a protective covering until the pressure sensitive adhesive is needed. Think of the shiny paper that carries a sticker or label.
A release liner’s base may be paper, polycoated paper, film, or even a metalized film. The liner can be coated with silicone or non-silicone to ease separation from the adhesive. It all depends on the precise delivery and dispensing system needed for the application.
In many cases, the release liner is one of the most critical decisions when designing a PSA. It has to have the right qualities and features to precisely match the application (hand applied or automatic dispensing) and processing (slitting, die-cutting, etc.).
The good news is you have options.
What Are the Different Types of Release Liners?
- Paper — The most common release liners, paper is offered in four main types: Densified Kraft (DK), Extended Densified Kraft (XL), Polycoated Kraft (PCK), and Extensible Polycoated Kraft (EK).
- Film — Film release liners are steadily increasing in use, especially for labels and tapes, and for industrial (roofing shingles, insulation products) and medical/hygiene (electrodes, wound dressings, diapers, etc.). Film liners generally have two types: Polyester (PET) and High-Density Polyethylene (HDPE).
- Specialty — These release liners include specialized film (such as metalized film) and other unique substrates for highly specialized applications in various industries (aerospace, automotive, wind energy, etc.).
Manufacturers coat a release agent on liners (often silicone but not always) to laminate and protect the adhesive it is applying to from exposure before use. The “release level” is the degree of separation of the adhesive from the substrate, and it ultimately dictates the characteristics of the release liner.
Here’s an example. A print company is preparing inkjet cartridges. It’s crucial to the automated assembly process that the release liner performs well so it releases from the liner and accurately dispenses onto the cartridge.
Matching a Release Liner to the Application
Pairing your custom converted adhesive part with the optimal liner is crucial for many applications, including automatic assembly processes. There are many different types of release liners that are compatible with adhesives:
- Easy, medium, or tight release
- Single- or double-sided release
- Printed
- Medical grade
- Extended liner for easy removal
- Split back
- And more
When it comes to release liners, it’s best to work with an experienced converter that handles many different types of material and also invests in understanding your product from start to finish.
The best converters can also adjust to working with customers who supply their own materials and/or release liner for a converted part. If you have any questions or comments about release liners, contact Strouse. Or, ask an engineer about adhesive solutions today!
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