Cationic Radiation Cured Coatings: Physico-Chemical Properties Related To Formulation And Irradiation

INTRODUCTION
Within the radiation curing industry,' photopolymerization of organic coatings induced by cationic
initiation has acquired real commeicial interest and stimulated many investigations in various
application fields. This is particularly due to the distinct of cationic UV-curing over the
other techniques of radiation curing.

As a consequenceof its high reactivity in the presence of UV-activated onium salts, the keystone of
most cationic !UV-curable systems is the cycloaliphatic diepoxide resin: the 3,4-epoxycyclohexylmethyl-
3',4'-epoxycyclohexane carboxylate, which will be referred to "ECC'. Since it is compatible with a
number of chemicals and resins of different generic natures, used in distinct systems of the coating
industry, the formulation latitude for cationic radiation curable ECC is very broad.

Of particular interest is the possibility of blending ECC with a wide range of hydroxyl-containing
compounds.' The latter copolymerize with the epoxide by acting as chain transfer agents, generally
improving the formulation cure speecP according to their characteristics (molecular weight,
OH-functionality,...), thus leading to a broad scope of, chemical and physical properties.