3.5Substrates

HPL up to a thickness of approx. 3 mm requires a substrate. The substrate has to meet different properties. In particular, it has to be rigid and has to have a smooth surface. This is an essential prerequisite for good visual appearance. The choice of a suitable adhesive, the amount of adhesive applied as well as the contact pressure and temperature for bonding also have considerable influence on the appearance and surface of the composite element. Like many other materials, HPL reacts to temperature and humidity fluctuations with dimensional changes. 

These can be different to those of the substrates and the adhesives and have to be taken into account during processing.

The following table lists some materials as examples of what can be used as substrates:

Table 5: Substrate materials, material types and subgroups

Special panel types, e. g. with higher resistance to humidity or flames, are used for special applications. In individual cases they may require special processing conditions. It is therefore recommended to consult the panel manufacturers.

The following aspects additionally have to be taken into account:

• Use appropriate adhesives
• Regulations applicable to the end product, e. g. CE marking
• Requirements regarding emissions, e.g. formaldehyde
• Guidelines applicable at the place of use
• Press temperatures and pressures
• The surface soundness of substrates has to be sufficient
• If necessary, carry out calibration sanding on the substrate
• Adhesives may penetrate (absorb) into the substrate, causing unsatisfactory bonding quality
• The components have to be stored in the same climate before bonding
• Processing guidelines have to be observed, e. g. from the adhesive manufacturer

Composite elements made of HPL and mineral substrates have a wide field of application and are often mandatory where increased requirements for reaction to fire have to be met, e.g. for high-rise buildings, ship building or public transport.