Adhesives are used in a wide variety of applications. Toilet paper is glued to the cardboard tube, food packages are sealed shut and labels are glued on. To ensure good adhesion, you must avoid air bubbles when pumping adhesives. Air pockets are one of the most common enemies to adhesive fluids. In this blog post we will explain what causes air bubbles to form in adhesives, and how to avoid them.
First of all, why are air bubbles a bad thing? Think of a ketchup bottle that is almost empty. When you squeeze the bottle, the little amount of ketchup that comes out is usually splattered and sprayed everywhere. It is not evenly dispensed from the bottle. The same concept applies to adhesives. If there are air bubbles in the fluid, the glue will not be evenly applied to the final product, resulting in poor adhesion.
Air pockets naturally form when the fluid is so thick and viscous that it folds over itself and doesn’t allow air to escape upwards. They can also be caused by chemical reaction, or if there is excessive air pressure applied to the adhesive in the process. When excessive air pressure is applied, the air can dissolve into the adhesive.
Air pockets can also become trapped in fluid lines when an empty container is removed and replaced in a dispensing system. To avoid these bubbles entering your adhesives, you should purge the line after you refill or replace adhesive containers.
Leaking pumps, pipes, and valves can also introduce air to your adhesives. If adhesive fluid is leaking out of your system somewhere, air is guaranteed to enter from that same location.
If you do find air bubbles in your adhesive material, do NOT use a vacuum to remove the air bubbles. Using a vacuum may remove constituents from the adhesive, changing its performance and reducing its shelf life.