IMAGING IN EVALUATION OF POLYMER-COATINGS ADHESION TO GLASS AT HIGH HUMIDITY

Adhesion reduction occurring after polymer coated glass was immersed i n water was studied in a variety of UV-cured urethane acrylate coating s containing alkyloxysilane adhesion promoting additives. It was obser ved that water accumulated under the coating surface in drops and form ed 'blisters' in the glass-polymer interface. A non-destructive imagin g technique was developed to measure the average size of the water bli sters. The size of the water blisters within the interface was correla ted with the wet adhesion force measured by coating resistance to 180 degrees peel. The force of coating resistance to 180 degrees peel off glass surface decreased non-linearly with the increase of the average size of the water blisters. It was concluded that the decrease in adhe sion between the coating and glass was a result of stretching and brea king of the silane bridging bonds and polymer fibrils by water condens ing on the glass surface within the polymer-glass interface. The mathe matical model relating coating wet peel resistance force with the size of the debonding produced by water accumulation was presented.