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Pressure-sensitive adhesives and tapes

Why is it pressure-sensitive adhesives that work in tapes?

Technologies

Pressure-sensitive adhesives ensure that adhesive tape can bond with the slightest of touch. The combination of various properties makes it effective.

there is a good reason for why it is pressure-sensitive adhesive that makes adhesive tape sticky. Or actually there are multiple reasons that make pressure-sensitive adhesives and thus adhesive tape an ideal partner for many applications.

What Is Pressure-Sensitive Adhesive?

To start with, pressure-sensitive adhesive is a kind of adhesive. More precisely: the adhesive that is found on adhesive tape. Pressure-sensitive adhesives have a special formulation: They combine viscosity - the state of being thick, sticky, and semi-fluid in consistency like honey for example - with elasticity - like rubber has for example. They adhere well on a surface (adhesion) and are equally solid and stiff in and of themselves (cohesion). In order to achieve that, the adhesive substance must consist of specific raw materials.

For example, natural rubber can be added since it has especially strong adhesion through the inclusion of resins. Adhesive tape on a natural rubber basis is applied, for instance, when we need to cover surfaces for painting work or seal up boxes. If adhesive tape must stick for a particularly long time, withstand UV sunlight and extreme temperatures, then pressure-sensitive adhesives made of acrylate are usually used. They can be adjusted even better to the specific requirements because acrylate consists of synthetic polymers that can be "tailored."

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Pressure-sensitive adhesives combine viscosity and elasticity

The production of transparent adhesive tape (i.e. tesafilm®)

Let us stick with the example of natural rubber and look at the production of a single-sided tape to keep it simple. After the large ball of natural rubber raw material has been reduced to small pieces, it is mixed with resin and other materials, dissolved and homogenized. The additional materials are selected according to the specific requirements for adhesives, in order to achieve, for example, high resistance to ageing. A water-based technology patented for tesa makes this process largely environmentally friendly without adding solvents.

After the production of the adhesive, in a special production facility the adhesive and backing are combined into one unit. The process works as follows:

Make way for tesafilm®: 1) Corona Treatment: Improves the pre-coat’s hold on the raw film, which is made of polypropylene and measures 5,000 m in length and 1.33 m in width, 2) Pre-coat: The pre-coat is applied to the film backing in a pan roller. This gives the adhesive a better hold later on. Then a scraper removes the excess pre-coat, 3) Drying: The film backing passes through five temperature zones, where the water in the pre-coat evaporates, 4)This stage evens out warping so that the film stays smooth under tension and does not wrinkle, 5) Web edge control: The web is realigned with precision accuracy – this keeps it running straight on track the rest of the way without slipping off to the left or right, 6) Post coat: The adhesive is applied using a pan roller and a deflection roller that can be lowered. At this stage as well, a scraper then removes excess adhesive, 7) Drying: The adhesive, which is still watery, passes through 12 drying zones. The temperatures rise steadily at first and then drop back down towards the end, 8) Winding and slitting: The 5,000-metre tesafilm® is wound around a core to form a large roll. After that, it can be cut to widths of 12, 15, or 19 mm and various lengths.
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In 8 steps to the final product:
  1. Pre-treatment: If necessary a pre- or corona treatment improves the pre-coat`s hold on the new backing material, which is made of polypropylene and measures 5,000 m in length and 1.33 m in width,
  2. Pre-coat: In the pre-coating process, a primer is applied to the backing. This gives the adhesive a better hold later on. Then a scraper removes the excess pre-coat,
  3. Drying: The pre-coat is followed by a brief drying process: The backing passes through five temperature zones, here the water in the pre-coat evaporates,
  4. Roller station: This stage evens out warping so that the film stays smooth under tension and does not wrinkle.
  5. Web edge control: The web is realigned with precision accuracy – this keeps it running straight on track the rest of the way without slipping off to the left or right
  6. Post-coat: The adhesive is applied using a pan roller and a deflection roller that can be lowered. At this stage as well, a scraper then removes excess adhesive.
  7. Drying: The post-coat is followed by a final drying process. The backing covered with adhesive, which is still watery, passes through 12 drying zones. The temperatures rise steadily at first and then drop back down towards the end.
  8. Rolling: Finally the finished adhesive tape is wound onto large rolls and converted. That means, in a final working step it is cut into various sizes (length and width), wound onto the appropriately standardized roll cores and packaged.
Adhesive tapes are pressure sensitive. That means, it requires “pressure” to ensure bonding.
Adhesive tapes are pressure sensitive. That means, it requires “pressure” to ensure bonding.

Why does adhesive tape bond?

Why exactly is pressure-sensitive adhesive included in the adhesive tape? There are primarily two reasons for this. What is pressure-sensitive adhesive above all?

  1. Permanently tacky/gluey.
  2. It has so much stickiness (we call this "tack") that the low pressure is sufficient in order to bond the adhesive tape to a surface.

While in the case of liquid adhesives we cover the surface and must wait until the glue becomes hard, the pressure-sensitive adhesive solidifies the moment we press it with our little finger. Pressure-sensitive adhesives provides everything that you value in a good work colleague: they are always at the ready. And they do their job reliably and highly effectively.