Part 3: Why You Have Voids in Your Cured Adhesive

Voids typically due to air entrapment while mixing.

The problems with voids in your cured adhesive include:

  • Pitted surface (Figure 1)
  • Reduced bond strength
  • Decreased environmental resistance
  • Lower thermal and electrical conductivity
adhesive-voids

Figure 1: Cured adhesive with voids (left) and properly degassed (right)

Why voids occur

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.

whipped-adhesive

Figure 2: Whipped in air

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.

Removing bubbles through vacuum degassing

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.

Figure 3: Adhesive mix before and after degassing

Figure 3: Adhesive mix before and after degassing

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.

Let Appli-Tec remove your adhesive mixing headache

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.


Learn More

wooden-sticks Part 1: Variables in the Mix Process

Three of the more common variables of the mix process that can lead to potential failure.

thermometer Part 2: Why Temperature and Humidity Affect Your Mix

Temperature and humidity greatly affect viscosity, pot life, adhesive performance, and cured properties.

vacuum-degassing Part 4: Vacuum Degassing

How vacuum degassing can introduce contaminants into your mix – often unknowingly.

appli-tec-adhesive-safety Why Work with Us?

Improve workplace safety and reduce costs by having Appli-Tec mix your adhesives.

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