Posted By Cheever Specialty Paper & Film on 01/06/2017 Manufacturing

Release Liners - Not Just Trash
You Throw Away

By: Jeff Ell

Release Liners - Not Just Trash <br> You Throw Away

Information on paper & silicone release liners including what are release liners, what properties do they have & how release liners are used. 

Many people think of release liners as trash you throw away after you have removed it from a product. But release liners are critical components of many different types of products, whether as carrier sheets in manufacturing or as “the anti-adhesive” as differential release liners in a multiplicity of industries.

All though several variables can impact the performance of release chemistry, we often are dealing with 5 Key variables. These variables affect how your tape removes from the release liner. We have written this paper as an essential primer on how release liners work. We do get somewhat technical, but we wanted to start with the core facts and basic principles presently available to most end users.

With so many different products using release liners we are often asked - "what exactly do you make." As a supplier in this industry, over the years, the best answer I have come up with is — we sell Performance.

Release Liner Performance

Why do we focus on Performance? We spend a lot of time finding the right adhesive and substrate for a given application. Release liners are often the last part of the total product design. Delivering the correct adhesive is critical to the end user because so much is riding on this single aspect of the release liner function. And unless it is a self-wound tape, the release liner usually finds its way to its final destination — A Dumpster.

Not to think of our industry or products as "trash," but some of the best products are at their best when the customer does not even notice it, the release liner that is.

The Top Five Variables

All though several variables can impact the performance of release chemistry, we often are dealing with the following five variables. These five variables will affect how your tape removes from the release liner. Further detail on each of these variables can be found on the TAPPI web site or searching these topics on the Internet.

  1. Cure Type 
  2. Additives and Cross-linkers 
  3. Peel Speed 
  4. Aging Time 
  5. Aging Temperature

We will explore these variables using components that are typical in the tape industry and see the results in a standard tape application.

The Basics of a Silicone Release

So if you do not read anything else in this article, reading this section will be helpful. Here is where everything starts, and you need to know the tools or options you have available. The two tables below show the Different Methods of Silicone Release Manufacturing and Components in Silicone Release Coatings.

With these charts, you can quickly recognize you have several options to choose. You need to define the curing process and a catalyst to work with the cure method.

Release Liners: Not Just Trash You Throw Away (Part II)

1. Cure Type

A "premium" or "Easy" release is a typical request in the release liner industry. Meaning it is easy to peel off. Where a "tight" means the release is hard to "peel" off, we will discuss more on the peel test later in the paper.

Using the chart in Part I of this series as a reference, here are some guidelines for finding the correct cure type. Achieving the proper cure type is a result of using a common industry standard of solvent acrylic adhesive.

  • Under an Energy Cure, EB (Electron Beam) has the tightest release cure type. 
  • Under the Thermal Cure, Solventless Platinum blends have the lowest release or "easy" release. 
  • EB and Tin are not good choices when you are looking for a "premium" or easy release

2. Additives and Cross-linkers

Control release additives are in use on their own to create single-sided tapes; they are common in conjunction with a premium release blend to create differential tapes. Mixing reactive silicone polymers, catalysts, and cross-linkers together, therefore, initiates the curing process.

Functional groups are usually incorporate into the polymer for chemical reactivity reasons (e.g., crosslinking). This type of chemical reaction is desirable to minimize the adhesives film's thermoplastic response and maximize its tensile properties. As an example, you can modify and improve bond strength and other properties by adding multivalent metal ions in a suitable form to promote ionic crosslinking.

  • The selection of cross-linkers in Solventless platinum systems can play a significant role in determining how your adhesive releases.  

  • Additives influence the chemistry and physical interaction of the formulation components. They affect the base polymer (e.g., initiators, cross-linker, and filler) or the dispersed polymeric system.

3. Peel Speed

When discussing applications, there are two general categories: machine and hand dispensed. You will come across this reference in a lot of spec sheets regarding a release level. In the release liner industry, a typical peel speed referenced for hand-dispensed products is 300 ipm (inch per minute held at 180-degree peel angle).

  • The rate at which you remove adhesive can significantly impact how release chemistry performs with a given adhesive.

  • It is important that the test method used will simulate as closely as possible the dispensing conditions.

4. Aging Time

Often it 's hard to predict when the consumption rate of the tape you have made. Understanding the aging time is critical to comprehend how the tape will behave over time.

Will the tape see normal turnover? Will it sit on a shelf at room temperature or high humidity etc.? Could it be there for six months or longer?

Simulating these conditions can be challenging, but depending on the end use of your product, this type of testing is usually necessary. To obtain predictable results, something as simple as subjecting the release liner or tape to an enclosed heated area will be helpful.

5. Aging Temperature

Temperature is important in situations when you produce the product indoors at room temperature and then shipped it via truck, train or plane, in cold weather. Or the reverse, shipping the tape in high heat. Temperature changes can have an impact on the performance of the tape by the time it reaches your customer.

SUMMARY

Here some general guidelines that you can take away from this paper.

a. Even if the cure method, adhesive, and release polymer type are the same, one can't assume identical performance

b. In looking for an "easy' or "premium" release, starting with a UV free radical or Platinum thermal system is a good starting point.

c. Products stored at higher temperatures may have a shorter shelf-life, so and understanding of storage conditions is essential

d. Understanding how a differential tape behaves under end-use production conditions is critical in avoiding adhesion confusion or too tight of a release.

e. Release values will rise over time but tend to plateau if there is no chemical interaction between the adhesive and release chemistry.

Finally, it pays to keep in mind and give extra attention and time to the Release Liner part of your project — it can save you from putting your whole project in the Dumpster!

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