The adhesive force

Adhesion describes the adhesive force that prevails at the contact surface between the adhesive and the surface to be bonded. High adhesion therefore means that the adhesive tape has strong adhesion to the substrate.

However, good adhesion alone does not mean that the adhesive tape has good long-term adhesion!

The internal bonding strength

Cohesion describes the internal strength of the adhesive, i.e. how strongly an adhesive holds together within itself. So if the adhesive is very strong, it has a high cohesion. In this case, the molecules of the adhesive are firmly bonded to each other and hold together well.

By the way: adhesives with a low cohesion often leave adhesive residues on the surface after removal.

The initial adhesive strength

Tack is a form of adhesion and describes the strength with which the adhesive bonds to the surface to be bonded at the initial moment. If a strong and firm bond is formed even with brief contact and little pressure, the tack is high. In practical terms, it can be simplified as follows: the tougher the adhesive on an adhesive tape, the higher the immediate adhesion.

It can be advantageous if the tack is not high. This is desirable, for example, if you want to correct the position of the tape if it has been applied incorrectly, or if the tape is only to remain on the surface for a short time. It can then be removed without leaving any residue.

But beware: adhesive tape with weak initial adhesion can still offer excellent final adhesive strength!

Permanent bonding

For permanent bonding, cohesion and adhesion are paramount, as the strength of the bond is crucial. The strength of the adhesive force at the moment of initial contact (tack) is usually of secondary importance. The bond must be durable and stable, and external factors must not be allowed to influence it.

Temporary bonding

Temporary bonds, on the other hand, depend on cohesion and tack. High tack is required for immediate adhesion. High cohesion is needed to ensure that the bond can be removed without leaving any residue – this ensures that the molecules are firmly bonded together and do not "tear apart" when removed. Adhesion, on the other hand, does not need to be strong, as the bond will be broken again.