What are structural, tough, second generation, & reactive acrylics?

What is the difference between a structural, toughened, second generation, and reactive acrylics?

They are all structural acrylics!  Adhesives have so many common and technical names it can be difficult to know how to compare them.

Structural adhesives form bonds that can bear structural loads. Generally, structural adhesives are epoxy or acrylic.  If the adhesive is acrylic in nature, we call them structural acrylic adhesives.

Toughened adhesives contain a toughener, such as rubber or an elastomer.  The toughener reduces the likelihood of adhesive fracture, thereby improving peel, tensile, and impact resistance.  Three common types of toughened adhesives are toughened cyanoacrylates, toughened epoxy adhesives, and toughened acrylic adhesives.  Toughened acrylic adhesives are also called second generation acrylic adhesives.

I prefer to avoid the term “reactive adhesive” because it could have multiple meanings.  Some people use reactive adhesive to define adhesives that cure – as opposed to dry.  Others use the term reactive adhesive to describe adhesives that form chemical bonds with the substrates.  Furthermore, others use the term to mean an adhesive that forms a permanent bond.

Another method of characterizing acrylics is by the manner in which they cure.

Characterization by Cure Method

1. Surface activated, (also known as Surface initiated, and Two part no-mix acrylics) –  These cure when you apply activator (initiator) to one surface and the acrylic resin to the other surface – upon joining cure begins.  These products develop strength rapidly – making them ideal candidates for high speed production.

2. Two component acrylics, 2K acrylics, 2 part acrylics are terms that usually refer to two components that require mixing of some sort.  Mixing via static mix nozzles is ideal.

3. Certain two part acrylic adhesives achieve enough mixing by dispensing a bead of one component on top of a bead of the other component and joining.

4. External mix specialty acrylic adhesives free-fall together about 15 inches above the parts.

For further help and advice, please contact Permabond.