OVERVIEW

The UV curing process is predominantly determined by the desired application of the coating. The intended end-product governs the substrate to be coated. This may be an abrasion resistant clear coat for ready-to-install parquet or an overprint varnish for paper cards, a coloured base coat and a clear coat for plastic automotive parts or metal coils, as well as a flexible protective coat for window frames. The function of the coating, for instance the colouration of the part, the protection against corrosion, scratching, chemical attack or against weathering deterioration, determines the type and property requirements of the coating as well as the thickness required.

The targeted properties, like high gloss appearance, abrasion resistance, colour effects, hardness, flexibility, resistance against chemicals or scratches, have to be provided by the chemical formulation, consisting of base resins, diluents, photoinitiators and various additives. Furthermore, an appropriate selection of the components has to be done in order to enable an effective curing process; for instance, in coatings containing pigments or UV light stabilizers, the spectral absorbance of the photoinitiator has to be adjusted to a spectral region where the pigments or UV absorbers are fairly transparent. This fine tuning is necessary to match the characteristics of the lamp system with the chemistry of the coating to provide an economic curing process.

Besides the physical properties of the cured material to be obtained, the economics of the coating process is the most important variable which decides over the type of coating used. Thus,...