It’s no secret that there are many kinds of pressure-sensitive tapes. A few examples we’re all familiar with include masking tape, duct tape and office tape, but numerous others also earn the name. Let’s discuss some of these different types of tapes, their basic properties and how to determine the best tape for your application.
How Pressure-Sensitive Tape Works
First things first. Most of us know what a pressure-sensitive tape is and how it functions in daily life. You simply apply the tape to the surface you want to bond to and apply pressure to adhere the tape.
What makes the tape work like this? Without getting too technical, the pressure applied to the soft adhesive forces the adhesive to “wet out” or flow over the bonding surface. This forms close contact between the surface of the pressure-sensitive adhesive and the bonding surface. That’s the mechanical portion of the adhesive bond. As the two surfaces join together, interaction occurs at the molecular level. The bond strength increases if the surfaces are compatible or if they are of like energy.
Adhesive Systems and Performance Characteristics
Pressure-sensitive tapes generally incorporate one of the following adhesive types:
As a general rule, rubber adhesive systems provide a high tack and high initial bond strength. Nevertheless, they have limitations like temperature range, UV resistance and limited longevity due to oxidative degradation.
All adhesive systems can be formulated to provide different properties, but acrylic adhesive systems are probably the most versatile in this regard. Acrylic adhesives have some performance advantages over rubber systems such as better resistance to sunlight and UV radiation, superior longevity, increased plasticizer resistance and good performance over a wider temperature range. Their typical temperature range is -40 F to 200 F. High shear properties – also known as vertical holding power – and adhesion to low-energy surfaces are other performance characteristics that can be realized with this kind of tape.
Silicone pressure-sensitive adhesives have some performance advantages over both rubber and acrylic systems. One of the greatest performance advantages of silicone adhesives is extremely high temperature resistance. Silicone systems can perform at temperatures topping a scalding 500 F. They also have a long performance life, bond well to silicone surfaces other adhesives won’t bond to at all and remove cleanly from most surfaces. The big disadvantages of silicone are poor vertical holding power (shear), low peel strength and high cost.
Pressure-Sensitive Tape Constructions
Now that we have an understanding of adhesive basics, let’s talk about the various pressure-sensitive tape constructions.
First in the lineup is single-sided, self-wound tape. For this tape, the adhesive is coated on one side of the carrier, which frequently takes the form of film, paper or a non-woven material, while the tape is wound into a roll. Duct tape and masking tapes both fit into this category.
Next, there’s single-sided tape with a release liner. This construction is a carrier, again a film, paper or non-woven material, with adhesive on one side. The adhesive layer is covered with a release liner. The release liner is then removed before the tape can be used. Double-coated tape, meanwhile, consists of a similar carrier but with adhesive on both sides. One of the adhesive layers is covered with a two-sided silicone release liner. To use this kind of tape, you unwind the roll and apply the exposed adhesive to the desired surface. Then you remove the release liner and apply the second side to the desired surface.
Transfer adhesives aren’t very common for general consumer use and, therefore, many people don’t know much about them. Basically, transfer adhesives are a pressure-sensitive adhesive cast directly onto a release liner. They have no carrier at all. Transfer adhesives, also known as transfer film, are primarily used for lamination to materials. Transfer adhesives perform just like a double-coated tape and can be used to laminate films or other carriers to make a pressure-sensitive tape or to bond two materials together.
Everybody can point out office tape in a lineup. It’s that little roll of tape on your desk used to attach two pieces of paper together or, more creatively, to pick up lint off your favorite sweater. Office tape is single-sided, self-wound film tape. Because this tape is a commodity product, cost is a major concern. Most office tapes utilize a low cost/low performance rubber or acrylic adhesive coated onto a thin, low-cost film. The tape is self-wound for easier use and there is no liner to throw away.
Masking (or painting) tape is similar to office tape in that it’s self-wound and has no liner for easier use. Its paper and adhesive are designed specifically to perform during painting projects. Masking tapes are very cost competitive, so rubber adhesive and low cost paper carriers – backing – are generally used. However, in order to perform well, masking tape adhesives are formulated to provide good adhesion while also maintaining clean removability. Their paper backing has a moisture-resistant coating to prevent paint from bleeding through it.
Duct tape is also a very competitive product, so low-cost materials are used to craft it. This means almost exclusively a permanent rubber adhesive system applied onto a low-cost vinyl coated cloth backing. Duct tape has an aggressive, high tack, permanent rubber adhesive, which allows it to stick to almost anything. The cloth backing provides the needed strength during use.
The three examples just mentioned illustrate how one adhesive system – rubber – can be formulated to perform differently depending on the need. The same holds true for acrylic and silicone systems.
Some single-sided adhesive tapes cannot be used in a self-wound format. Instead a liner is needed when the end use requires stronger performance or processing requirements. For example, imagine a customer wants to make small parts that are cut into shapes and needs pressure-sensitive tape to adhere to one side of those parts. In this scenario, the release liner functions to cover the adhesive and allow the die cutting of shapes, yet it also provides the peel-and-stick function for ease of use.
Double-coated tapes are generally used to provide a simple way to mount something or bond two materials together. For instance, a manufacturer of foam weather stripping may request a pressure-sensitive tape on one side of the foam to allow for ease of installation by the consumer and long-term performance of the part. Weather stripping foam profiles are usually constricted, two inches wide or narrower. A double-coated tape with a film carrier in this example will provide dimensional stability, keeping the foam from stretching too much and deforming during the lamination process. The film also adds strength to the finished weather stripping part. Using an acrylic adhesive system here offers a strong bond, UV resistance, performance under a wide temperature range and product longevity during use and storage. Covering the adhesive with a paper or film release liner likewise adds a peel-and-stick feature for easy application. In fact, tapes for extruded parts frequently use film release liners to assist in preventing part deformations due to moisture.
As discussed earlier, transfer tapes are often used for wide-width lamination of different materials, such as paper, film, foils, foams and fabrics. The transfer tape is adhesive coated directly onto a release liner, and it performs much like a double-coated tape, but without the same dimensional stability properties. Transfer tapes can be made with any pressure-sensitive adhesive type. Some of the benefits of this tape format are:
- No carrier film, which aids adhesive penetration into rough or porous materials like foam. This also provides tape flexibility, assisting lamination to thick and flexible materials without causing creases as a double-coated tape might do.
- Laminates two materials together without adding the extra thickness of a carrier material.
- Offers flexibility to laminate to a wider range of materials.
The world of pressure-sensitive tapes is wide and can be complex, but we’re always here to help you sort through the jargon and select the right kind of adhesive for your needs.