Differential adhesive tapes are a specialty form of pressure-sensitive tape (PSA tape), and the name essentially refers to the fact that they have different adhesive systems on each side. Their most common use is as a bonding agent between two surfaces that require different types, or levels of adhesion. They can also be designed where one side is a permanent bond and the other is removable / repositionable.
These differential tapes can be used in a wide range of industries and applications, from medical to industrial to automotive and aerospace, where different surfaces need to be joined. There are many versions of differential adhesive tapes, but one of the most common and high performing is silicone adhesive on one side and acrylic adhesive on the other (silicone / acrylic differential). This design offers distinct advantages for different types of specialty applications. Let’s explore how these silicone / acrylic differential adhesive tapes work and the benefits they provide!
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To understand the benefits of this unique differential construction, it is important to know the performance advantages of each type of adhesive (PSA) used, as well as the other components in the tape structure (carrier and liner):
Silicone Adhesive
Silicone PSA is well known for its excellent performance through a variety of unique features:
- Repositionable/removable – the adhesives can be specially formulated to be initially repositioned, or ultimately removed cleanly if required.
- Chemical resistance – silicone adhesives are an excellent choice if the applications require resistance to chemical or solvent splashes or immersion.
- Temperature resistance – of all adhesives, silicone has the greatest ability to perform in temperature extremes, ranging from -100F to 500F.
- Electrical insulation properties – silicone is a naturally insulative (dielectric) material, and therefore, tapes made from it are good insulators and RFI shielding.
- UV resistance – silicone adhesives are less prone to UV degradation than other adhesive systems.
- Moisture resistance – silicone adhesive holds up well to water and other liquids and maintains a bond.
Having silicone on one side of your differential tape means that it will have one, or several, of these high-performance benefits. A very commonly used characteristic that makes silicone adhesive so valuable in a differential is its ability to bond well to silicone (and other difficult surfaces), meaning that it can help bond silicone foam, silicone rubber, and other low surface energy (LSE) materials to different, dissimilar, surfaces – (e.g. a silicone foam or rubber gasket bonded to a car chassis or other high surface energy (HSE) part.)
In contrast to this type of permanent bonding application, the other unique aspect of silicone PSA that is commonly employed is its removability / repositionability. By utilizing a highly stable, removable silicone on one side, and a permanent bonding acrylic adhesive on the other, many materials or parts can be turned into a removable item – (e.g. removable foam protection blocks for automotive, electronic parts, etc.)
Acrylic Adhesive
Acrylic adhesives are very common, versatile, high-performance PSAs. They can be formulated to have a wide range of tack, adhesion, and shear properties. While their ultimate temperature performance, and some other properties, are not quite as high as silicone, they typically have higher tack (quick stick) and adhesion (ultimate bond strength) to most materials. Because of their good bonding properties to (non-silicone) surfaces, they are the ideal counterpart to silicone in a differential tape when bonding the other side to common engineering materials (e.g. steel, foams, rubbers, etc, etc.).
Carriers / Backings / Substrates
There are several terms for the material that the two adhesives are coated on. The most common in the tape industry is ‘carrier,’ but it is also sometimes referred to as the backing or substrate. While the adhesives do all the bonding work, the carrier is critical to the performance of the tape and must have complementary properties to the PSAs. It also has to be coatable with the relevant adhesive types and withstand the coating processes, while also having the appropriate properties for the end application (e.g. temperature performance, tensile strength, die cutability, etc.)
There are a wide range of carriers that are used for adhesive tapes, and common ones for silicone / acrylic differentials are polyester (PET) film, polyimide (‘Kapton”) film, and a variety of non-wovens.
Liners
The final piece of the design puzzle for differential tapes (and in fact most double-coated tapes) is the release liner – the material that covers the adhesives during the process and transportation to the final application and is ultimately stripped away before the adhesive tape is used (think of the paper strips that you take off a finger bandage before you use it).
For differential tapes, especially silicone / acrylics this is more of a challenge than typical double-sided tapes as you have two different adhesive chemistries to release from. Developers at tape manufacturers can solve this challenge through very custom release liner formulations, or by having two liners (‘double linered’) – one specifically for the acrylic side, and one tailored for the silicone side, with releases designed to match the adhesive and end-user needs.
Other Differential Tapes
Adhesive Applications offers other types of differential tapes to solve customers application challenges. Examples of these include acrylic on one side and rubber adhesive on the other (rubber/acrylic differential) for applications where high tack / quick stick is required, and also acrylic adhesive on both sides but differentiated by different acrylic formulas or coating thickness to specifically bond to different types of surface.
Conclusion:
It is clear to see why differential adhesive tapes are an essential tool in many industries due to their superior performance compared to traditional adhesives and tapes. In addition, silicone/acrylic tapes have the added advantages of the unique, high-performance attributes of silicone combined with the versatile tack and bonding strengths of acrylic in an ‘apply and done’ tape format, allowing designers and specifiers to bond difficult, dissimilar materials, and design high-performance removables for the most demanding applications. With their unique combination of qualities, these versatile tapes can help you achieve better results with fewer complications no matter what application you’re working with!
Selecting the correct material combination to provide ideal bonding or sealing can be a complicated task and requires expert knowledge of the materials involved. If you’re looking for a reliable partner for your next assembly, high-performance bonding, or sealing project, reach out to Adhesive Applications at info@adhesiveapps.com or call (413) 527-7120.