OVERVIEW

The raw materials described in this section are classified into the categories of radical polymerization systems, cationic polymerization systems and radical polyaddition systems (Thiol-ENE).

The raw materials used for the formulation of UV coatings consist of low molecular weight resins, typically in the molecular weight range of 300 5000 g /mol. The main resins types are radically polymerizable unsaturated polyesters, acrylate terminated molecules, like polyepoxides, polyesters, polyethers and polyurethanes as well as epoxides and vinylethers. Epoxide terminated oligomers and vinyl ethers are cured cationically. An overview of the main resin types used in UV curable systems is given in Figure 4.1. By far the most applied resins are the radical polymerization type acrylates and unsaturated polyesters, the thiolene systems are often discussed because of their insensitivity against oxygen inhibition, but yet only used in few niche applications.1 The cationic polymerization systems are also used only in a few metal coating applications, whereas the photoinitiator-free systems are just in the developmental stage.