Choosing an Adhesive - Part 2: Texture Counts

When it Comes to Sticking, Less is More

When choosing a laminating adhesive to put on the back of a Lexan control panel, most people would intuitively choose the thicker adhesive laminate over the thinner. After all, we live in a "If one is good, two must be better" society.

But in the case of laminating adhesives, thicker is not necessarily better. Indeed, for the most part, the thicker the adhesive, the less effective the bond. The only time that thicker adhesives will be more effective is when you are dealing with a textured surfaces.

You can think of it this way. The job of the adhesive is to "link" one surface to another. Imagine two strong men floating in the ocean. Each man is holding on with one hand to the lead line to the bow of their own two boats. Now those two men "link" their other arms together to hold the boats near each other in the moving water. They are very strong, and they manage to hold the boats in close proximity.

But now imagine that three more men, just as strong as the other two, want to get into the act. So they place themselves between the first two men, everyone linking arms and forming a chain of five men between the two boats. Now no individual man is stronger or weaker than any other, but we have added three man to man links where we only had one before. Counting the links to the boats, there are six where there used to be just three. The boats are much more free to move about, and there is a much greater probability of a link breaking.

This is what a thick adhesive does to weaken a bond, when compared to a thin layer of adhesive. The adhesive link from surface to surface is strong. But the multiple links from adhesive to adhesive molecule in between is weaker.

The exception to this rule is for highly textured surfaces. This is simply a matter of contact area. If the thin adhesive cannot "flow" into the depths of the "valleys" between the high points of the textured surface, then there will be less surface area to bond to. In that case, you want a thicker adhesive to flow into those valleys, and form a more complete bond.

MaverickLabel.Com offers two thicknesses of laminating adhesive for Lexan control panels. 3M 467MP is the standard for the control panel industry; it is 2 mils thick, and will be the best choice for almost any application where the control panel is being adhered to a reasonably smooth surface (including powder coated surfaces). 3M 468MP is the exact same adhesive as 467MP, but in a 5 mil version. It will flow into roughly textured surfaces that might be found in rare application. (Note: our LSE adhesive is a specialized 2 mil adhesive for adhering to LSE plastic surfaces, covered in part one of this article.)