The problems with voids in your cured adhesive include:
Stirring – Mixing multi-part adhesives requires a great deal of stirring, a process that whips in a lot of air, as you can see in Figure 2.
Viscosity – Thicker adhesives inhibit the ability of bubbles to migrate to the surface.
Fillers – Fillers have micro air bubbles attached to their surface.
Heat Curing – Micro-bubbles expand during a heat cure process. Sometimes many small bubbles combine to make large voids.
Applying a vacuum reduces pressure, which enlarges bubbles and increases their buoyancy – allowing them to rise to the surface and escape.
Vacuum degassing can be static or dynamic. Mixing under a vacuum (dynamic degas) is the best way to remove trapped bubbles. In Figure 3, you can see the before and after of an adhesive mix that’s been degassed.
Vacuum degassing introduces another variable that can affect your mix: contaminants. In next month’s newsletter, we’ll cover the two main reasons why your vacuum chamber could be ground zero for contaminants.
Engineers rely on Appli-Tec and our packaged PMF adhesives because when a part fails, they know it’s not the adhesive.
Appli-Tec conducts incoming inspection, including FTIR validation, of each adhesive before its use. Our mixing environment is temperature and humidity controlled, and mixing is performed to a documented procedure with every lot number, quantity and time recorded.
It’s why you get consistent results, every single time.