In English, doc! How do adhesives work?

Laurie Gibbons
Adhesive Selection and Use, Tips
July 28, 2008

How do adhesives work? Some of us just don’t really care how adhesives work. They work, and that’s all we need to know. Some of us are what you’d call armchair scientists, and we read technical manuals full of terminology that reads like a foreign language to the average Joe.

Most of us probably fall somewhere in between. We like to know how stuff works, but we don’t want to attend a university of science.

So, for the curious layman, here are some general answers to the question, How Do Adhesives Work:

Obviously, an adhesive is a compound that will adhere, bond, or attach two or more items together (or it had better, if they don’t want us switching brands), everybody knows that. It’s the science behind it that not everyone is familiar with. Adhesives work in one of four ways. The most common are mechanical and chemical bonding…

Mechanical bonding

The simpler and more common form of adhesion. In mechanical bonding, the bond formed between the adhesive and the surface occurs when the adhesive works its way into the small pores of the surface. It acts as if millions of microscopic screws and bolts were driven into both surfaces to hold them together.

Chemical bonding

Chemical bonding is when an adhesive actually bonds with the surface on a molecular level. This would be the same thing as what happens when two atoms of Hydrogen bond with one atom of Oxygen, hence, H2O, or water. Certain chemicals are simply attracted to each other. Hydrogen especially has a tendency to bond with whatever other atoms it happens to find lying around.

The Seldom Used Alternatives

The third and fourth seldom used methods include the use of van der Waals forces, and moisture aided diffusion of the adhesive works into the surface of… well… okay the third and fourth are kind of difficult to explain in layman’s terms, and they’re not very common anyways, so let’s just talk about the first two for now.

A Little More on Mechanical Bonding

Mechanical adhesion doesn’t strictly happen on a microscopic scale. Velcro, zippers, pins, staples, safety pins, and buttons are all forms of mechanical adhesion. Mechanical refers to the fact that it is simply some physical shape holding the two surfaces together, like a pair of hands clasping tightly.

In glues and adhesives, the mechanical adhesion through the pores of the surfaces occurs thanks to the drying or curing process. When the glue goes on, it’s in a thin, liquid adhesive form, which still allows either surface to move freely. This liquid form also allows the adhesive to soak into the pores of the surface. When it begins to dry and become solid, it works, just as Velcro, as just a bunch of hooks holding the two objects together.

One More Thing About Chemical Adhesion

Chemical adhesion is more complex and only happens on a microscopic scale. It works by forming a compound between the chemicals of the two surfaces. The reason this form isn’t quite as popular for epoxy adhesive manufacturers should be obvious. Chemical adhesion happens all the time in nature, but it’s kind of a difficult thing to engineer at one’s leisure. Only certain chemicals can be easily bonded to one another, and manmade adhesives to aid in chemical bonding is still a relatively undiscovered frontier.

If you like to know more about how adhesives work, please contact Permabond.

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