Factors influencing the adhesion properties of radiation curable coatings on different substrates

The adhesion properties of UV-curabIe coatings based on a typical epoxy acrylate resin, modified by the presence of different reactive diluents or adhesion promoters, on several substrates (steel, glass, polycarbonate) were evaluated, The influence of some general factors like volume shrinkage, substrate wetting, and relaxation of the internal stresses was taken into account. Specific interactions between the coatings and the substrates were introduced by using adhesion promoters (monomers containing free carboxylic and phosphorus acidic groups) on steel or coupling agents (alkoxysilane monomers) on glass. In the case of polycarbonate substrate, adhesion was obtained through the presence of particular monomers able to interact with the substrate, thus suggesting a.diffusion-controlled adhesion mechanism. The results obtained are discussed in the framework of the different mechanisms of adhesion involved.