Coatings on wooden substrates for furniture, flooring and interior are a main application for radiation curing lacquers. Increased adhesion is an important target for development of UV coatings on wood. Superior adhesion leads to better whitening behavior (coin test) and abrasion resistance.
Guidelines to improve adhesion on wood are:
* Swelling of wooden fibres with waterborne UV primers to increase the substrate's surface area and its interaction with the coating.
* Better wetting of oily surfaces e.g., teak, mahogany or rosewood by using coatings with low surface tension.
* Chemical crosslinking of coating and substrate.
"From a theoretical point of view, adhesion is the result of the action of surface forces, of wetting and of the coating's curing process at the substrate coating interface."1 The porous nature of wood is a main difference in comparison to other substrates such as metal and plastics. The liquid coating material is partly absorbed into the wood by capillary forces.