PSA
Hot melt adhesives are adhesives based on Thermoplastic elastomer. These are characterised by the fact that they do not completely set, but remain permanently tacky. In this case, it is important to achieve sufficient wetting between the pressure-sensitive adhesive and the substrate. For this reason, this group of adhesives is known as “PSA – Pressure Sensitive Adhesive”.
In the BÜHNEN designation for hot melt adhesive, the first letter stands for the basis: D for Thermoplastic elastomer
The various applications for pressure-sensitive adhesives can generally be divided into three areas:
- Precoating: e.g. self-adhesive equipping of shipping cartons. Here, the hot melt adhesive is applied, provided with a protective cover and the bonding can follow at a later time.
- Inline adhesive process: e.g. lamination of insulation materials. In this case, the hot melt is applied and the bonding occurs immediately.
- Removable bonding: e.g. small sample bags in magazines. The hot melt adhesives have a reduced tackiness with equally high adhesion.
Bases for hot melt adhesives are thermoplastic polymers. A polymer is a chemical compound that consists of branched molecules or chain molecules.
“Thermoplastic” stands for the property of the plastic to become deformed at certain temperatures. In the case of hot melt adhesives, this means to melt when heated and to become hard again on cooling. Pressure-sensitive adhesives are one-component adhesives which physically bond.
In the case of some TPE adhesives, the adhesion is already so great in the cold state that adhesion is established even with light contact. The adhesion on the materials to be bonded reaches the PSA by the contact pressure – the higher the contact pressure, the better the adhesion produced.
Advantages of PSA hot melt adhesives
- Very good adhesion to low-energy surfaces, such as PE
- Solvent-free
- Universally applicable – wide range of adhesion
- Elastic adhesive joints - high level of elasticity
- High production speed due to short setting time
- Harmless to health and not subject to marking
Limits of PSA hot melt adhesives
- Low resistance to solvents and plasticizers
- Limited heat resistance
- Creep tendency with tension bonding