Effect of Siloxane Functionalized Caprolactone Polyols on Photocurable Epoxy Coatings

By Shaobing Wu, Mark D. Soucek

Cationic ultraviolet (UV) coatings were formulated using a cycloaliphatic diepoxide (3,4-epoxycyclohexyl methyl-3’, 4-’epoxycyclohexane carboxylate) with siloxane modified caprolactone polyols. Both di- and tri-TEOS (tetraethyl orthosilicate) functionalized caprolactone polyols were used to modify the UV coatings. The resulting coatings were cured and evaluated in terms of pencil hardness, MEK double rubs, crosshatch/pull-off adhesion, and reverse impact resistance.

Addition of the siloxane-functionalized polyols into the caprolactone polyol/cycloaliphatic diepoxide coating formulations improved pencil hardness, MEK double rubs, and enhanced toughness of the coatings.

When the addition of siloxane-functionalized polyols was less than 25 wt%, the resulting coatings had significantly increased adhesion. In addition, modification of the coatings with the siloxane-functionalized polyols also re-duced surface tension and improved film formation with reduced levels of surface wetting agent.

Without the modification, the coatings exhibited a poor balance of hardness and adhesion.