Remember triangles… those three-sided polygons you learned about when you were just a kid?

You may not have always called them polygons, of course, but we’re guessing at an early age, you could pick out a triangle on a page of brightly colored shapes of all sorts and sizes.

And now you may be wondering what in the world triangles have to do with tape…

What if we told you we couldn’t make tape without them?

Surprising? Intriguing?

Well, it’s true. In fact, we use a very special triangle – The Pressure-Sensitive Adhesive (PSA) Triangle – to help us balance all the properties that combine to create adhesives that work.

What Is the PSA Triangle?

We use the PSA Triangle to describe three characteristics of adhesives that are constantly in balance with one another as we develop tapes. Those three characteristics are adhesion, cohesion, and tack; and they all work together to create the specific properties of specific tapes.

Still with us?

Let’s break it down just a little more:

Adhesion - Adhesion and tack are easy to confuse because they’re similar – they both have to do with the stickiness of tape. But adhesion is the attraction between the adhesive and the substrate while tack is an initial contact. More on tack in a second…

What’s important to remember about adhesion is that it’s the strength of an adhesive to bond to a surface. Time is one of the key factors that affects the adhesion strength. One of cool things about tape is that unlike glues or epoxies, tape creates that bond almost immediately. Now, adhesion strength does grow over time, but the key is that you have a secure bond almost immediately.

Cohesion – We use the term cohesion to describe the inner strength of the adhesive. How well does it stay connected to itself?

And that really controls things like holding power or shear, which is important in mounting. If you apply force to the tape and use a downward or upward motion, the cohesion is really important for keeping the adhesive from breaking or moving.

So while adhesion is the ability of a tape to bond on the outside with another surface, cohesion is all about the strength of its bond on the inside, its ability to hold itself together.

Picture one big group huddle… on the inside of that tape! And a “Go team!” ringing out.

Tack – We’ve already mentioned tack briefly. It’s the characteristic people are probably most familiar with, and in basic terms, it describes how sticky a tape is and how the adhesive engages with the substrate it's adhering to. It’s really a surface level, initial stickiness.

Think fast… and furious. How quick does that tape grab a hold of the surface? That’s tack!

Together adhesion, cohesion, and tack form the PSA Triangle. And together, they help us make the best tapes on the market.

How Does the Triangle Stay Balanced?

Adhesion, cohesion, and tack all interact with each other, but different properties work best in different applications, so a tape is always trying to find a balance between all three – the balance that works best for its particular application.

It may be easier to explain with an example, so here’s how you can think about balancing the three properties:

We could say cohesion and tack are the most at odds with each other. As we increase cohesion, typically the tape itself is going to be less tacky. Now, remember ‘tack’ doesn't describe long-term adhesion or long-term hold – it’s all about initial stickiness.

So, in an application where we can use more force when we apply an adhesive, we don't need much initial stickiness – tack – for that application. That means we can lower the tack and increase the cohesion.

We may do something like this for a mounting application where we want strong cohesion because we want it to be able to hold a frame or a mirror on the wall for the long haul. Cohesion is going to be really good at that. It’ll make sure the frame or mirror doesn't slip over time and that the adhesive stays put.

Does that make sense? In a more permanent application where we can apply a little force to the tack, the initial stickiness is not as important as the strength of cohesion.

It really comes down to application and which property is most important for a particular tape. We balance the tapes based on those factors.

What’s Pressure Got to Do with It?

And did you notice that pressure matters, too? It is called a Pressure-Sensitive Adhesive Triangle, after all.

Pressure is pretty important to a Pressure-Sensitive Adhesive. And the reason is in order to make an adhesive work, we want as much of the adhesive to touch the substrate area as possible. Pressure lets us do that.

Believe it or not, the adhesive will actually conform to the surface of the substrate! That’s because our adhesives are viscoelastic. Their properties stay very solid on the tape, but as you pressurize them, they'll actually wet out like a liquid to get into all those little areas and make sure the contact is complete.

So when we apply pressure, the viscoelasticity takes over and makes sure ultimate contact between both surfaces is enough for the best bond possible.

How cool is that?!

Curious how to apply pressure and make all this cool stuff happen?

Well, the best way to do that really depends on the application and the tape. Certain tapes apply easily with hand pressure, just putting your hand on them or running your fingers along them. But some of our tapes benefit from a squeegee application. That requires using a square plastic piece to apply precise pressure in certain areas. Then some tapes – and this is more about where you're applying them – benefit from a roller application as well.

And that’s the scoop on the three-sided polygon – the PSA Triangle – that helps us make our tapes to exactly match the applications they’re made for.