Effect of siloxane functionalized caprolactone polyols on photocurable epoxy coatings

Cationic ultraviolet (UV) coatings were formulated using a cycloaliphatic d iepoxide (3,4-epoxycyclohexyl methyl-3',4-'epoxycyclohexane carboxylate) wi th 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 p encil 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% t he resulting coatings had significantly increased adhesion. In addition, mo dification of the coatings with the siloxane-functionalized polyols also re duced surface tension and improved film formulation with reduced levels of surface wetting agent. Without the modification, the coatings exhibited a p oor balance of hardness and adhesion.