Influence of the fused silica surface dehydroxylation on the adhesion of epoxyacrylate protective coatings used for optical fibers

Measurements have been made of the adhesion of liquid and UV-cured epoxyacrylates to a fused silica surface. The fused silica surface was dehydroxylated in the 200-900 degrees C temperature range. Also, the contact angles of water, diiodomethane and formamide on the fused silica surface were measured. Using the contact angle results, the 'harmonic mean' method and the acid-base interactions approach, the dispersion (Lifshitz-van der Waals) and electron donor and electron acceptor components of the fused silica surface as well as epoxyacrylate polymer surface free energy were calculated. It was found that, probably because of the physically adsorbed water, the hydroxylated surface of the fused silica is basic and that the adhesion of the epoxyacrylate polymer to this surface depends on its basicity.