3 Types of Adhesives Explained
Metin Ozsobaci· December 23, 2020
We hope when you hear tesa, you think ‘tape.’ Softprint, ACXplus, HiP & 4965… the list could go on and on.
We (the tape nerds!) want to be the go-to, one-stop solution for your tape needs.
So to be sure we’re covering all the bases, we stick to the basics. We rely on what’s worked for us for years, and that’s three main types of adhesive systems: natural rubber, synthetics, and acrylic adhesives. There are other adhesive types in our assortment, but today we’re going to talk about the Big Three!
Three you say? So…What are they and more importantly, what’s the difference?
We appreciate you asking!
Let’s dive right in…
1. Natural rubber
Natural Rubber is one of the most widely used products in adhesive tapes. In fact, it is the base adhesive we use in many of our general-purpose tapes because it is so versatile and reliable. But what is Natural Rubber?
Natural Rubber is a naturally occurring substance that is tapped from rubber trees. Similar to harvesting tree sap to make maple syrup from Maple trees, small grooves are cut into the bark of a Rubber tree. The fluid that flows from the grooves is collected, processed, and eventually turned into large blocks for shipping. But, it still isn’t an adhesive that you can use on your masking tape.
Natural rubber isn’t really tacky by nature. Once the blocks of rubber are melted into a liquid, and after resins, called tackifiers, are added, the rubber has a sticky feel that is the hallmark of general-purpose tapes. It doesn’t function as an adhesive until you add the resins, and once it is coated onto a backing-like paper for masking tape or cloth for duct tape, it can then fulfill its true purpose of protecting your project or securing your valuables! Molecularly, natural rubber forms long chains when observed under a microscope that overlap and mix with each other, looking like a plate of spaghetti. This spaghetti substrate provides a fast bond, but lacks resistance to external factors like UV, high heat or cold temperatures since the plate of spaghetti lacks any structure to hold itself together.
The reason why natural rubbers do extremely well for general purpose applications is that they need to work fast and by its “Spaghetti” makeup do they ever! Natural rubber adhesives are known to have a high initial tack that can be modified higher or lower by changing those tackifiers we spoke about earlier. This allows the adhesive to reach a maximum hold quickly while also working on a wide range of items, sticking securely!
Pretty cool, isn’t it?
2. Synthetic Rubber
Synthetic rubber is similar to natural rubber, but also decidedly different. The word rubber occurs in both names, so that is in common, but what makes it different? First and foremost, synthetic rubber is not natural. Wow, on to the next chapter!
But seriously, synthetic rubber is a chemical mixture that acts like natural rubber, but they’re not naturally occurring. tesa creates a compound in our production plants from chemicals to simulate the properties found in Natural Rubber, but because it is fully lab-produced we can address areas where Natural Rubber is lacking, specifically shear resistance. Shear is the measurement of gravity pulling on an item vertically attached to a wall, and resisting shear is preventing the item from moving while hanging. Pretty important for your wall mounted items to stay in one place, right?
Remember earlier when discussing the plate of spaghetti for Natural Rubber and how it resembled an unorganized pile of chemical chains? Well, Synthetic Rubber is still a pile of spaghetti, but because we can address some of its resistance issues through chemical intervention, the microscope shows a bowl of spaghetti and little blocks of styrene on the ends that look like meatballs! The styrene creates a hardening agent right in the middle of the rubber’s natural elasticity, adding resistance to various external factors by securing the chains together. That’s what provides the shear resistance.
So, with natural rubber, you have really good initial adhesion and tack. With synthetic rubber, you get the addition of shear, which is what we call Z-directional force. And it prevents slipping because of the additional hardness in the polymer.
What does that mean for you? It comes down to this. With adhesion, tack, and shear, synthetic rubbers are pretty close to an all-around win. With one exception. If you need all that to happen outside in the heat or cold and with other environmental factors at play, you’ll want to keep reading because we’ve got another solution for you…
Because while synthetic rubbers are great for sticking and staying in place, neither natural nor synthetic rubbers are UV-, temperature-, and environmentally resistant.
3. Acrylic adhesives
For our customers that require temperature or UV resistance in their adhesives, acrylic polymer-based adhesives are must go-to resource.
Acrylic polymers are lab-made large scale materials, and they’re tacky by design, which is a huge benefit. Thinking back to our plate of spaghetti, Acrylic polymers look nothing like spaghetti, because they have an organized structure to their chemical makeup. This is accomplished by something called cross-linking which takes the shorter acrylic chains and links them together, sort of like a chain link fence. The links form a resistance from breaking down because chains add more stability across the entire structure, just like a fence. This means that while natural and synthetic rubbers lack aging properties because there is no support in a pile of spaghetti, there's a lot more protection in an acrylic. Additionally, acrylics don't change colors. If clear is the desired performance, they do not yellow when you leave them out in the sun, and they have better temperature resistance as temperatures rise above the softening point of 75C or below a freezing point of 0C. They remain stable, which makes them a reliable performer outdoors in all conditions.
Acrylic adhesives don’t have quite as much tackiness as natural and synthetic rubbers because the cross-linking process lowers that result. But, since it is fully lab-made, we simply add tackifiers to the acrylics to provide UV-resistant adhesives that also have strong initial grab. We call them ‘tackified acrylics,’ and they aide in faster ultimate adhesion while only slightly reducing temperature performance. A win-win, even in Arizona during the heat or Western Canada in January. Acrylic adhesives are the go-to for demanding applications requiring the utmost confidence in their performance!
Not sure which adhesive is the best solution for your next job? Reach out to us.
We’re always happy to talk tape!