Enhancing the design bending strength of new and aged glass with a functional coating

Annealed glass is susceptible to stress corrosion. This stress corrosion phenomenon, also known as static fatigue, embodies a reduction of the tensile strength due to the combined presence of applied tension stress and humidity. As a consequence, the effective strength of annealed glass members in building construction is limited. According to the classical theory developed to account for this phenomenology and to previous experiences published in the literature, stress corrosion can be prevented by avoiding the interaction between water molecules and the silica network. In the present work an innovative polymeric coating cured by UV radiation is applied to the surface of glass specimens to prevent stress corrosion. This coating is suitable to constitute a barrier between humidity and glass surface, thus increasing the reliability of new glass structures and their resistance to long-term loads, due to a compositional profile that maximizes hydrophobicity and water vapor barrier on the air side and adhesive properties on the substrate side. Coating effectiveness is assessed experimentally in terms of load-carrying capacity of coated plates tested under equibiaxial bending conditions with the coaxial double ring setup. New and naturally aged glasses are analyzed. The results evidence an increase of the design bending strength between 60 and 90% with respect to the strength of un-coated glass.