Contact forces between two substances because of molecular interaction. 

Essential factor for a good stability of laminates, prints, covers and bondings.

In particular the adhesion forces between the molecules of a substrate and of a deposition must be bigger than the internal adhesion forces between the molecules of the deposite.

It is a most important application of plasma treatment to increase the surface energy, i.e. the adhesion potential of a substrate.

For more information click ⇒ Adhesive strength

The wetting of a surface by a liquid is essential for good adhesion.