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UV-curable powder coatings, combining of the attributes of the thermoset coatings and the radiation curing made possible the creation of environmentally friendly coating for heat sensitive materials including thermoplastic and wood 1-7]. Photochemical curing occurs by a free radical mechanism with unsaturated moieties or by a cationic mechanism with epoxy or vinyl functionalities. To date, most of the work on UV curable powder coatings has focused on free radical systems based primarily upon solid polyester (meth)acrylate and solid maleate/fumarate unsaturated polyesters. The coating is cured by a free radical polymerization of double bonds in the presence of suitable photoinitiator. UV — cationic curable powder coatings, on the other hand, are generally one component systems, that cure by a cationic polymerization in the presence of photo-acid generated initiators. Both systems have advantages and disadvantages. Acrylates and unsaturated polyesters, which polymerize rapidly by a free radical mechanism are easily modified allowing materials with an excellent of properties to be obtained. Although acrylic materials generally have superior weatherability, they are known to have poor physical properties (e.g. flexibility and impact resistance), create film defects in other powder coating materials and exhibit tendency to agglomerate during storage as a powder. Moreover, areas
not exposes to UV light do not cure and may remain tacky 8,9,1 0].
