Novel multifunctional coatings with photocatalytic and hydrophobic properties for the preservation of the stone building heritage

Mixtures based on aqueous solutions of nanostructured TiO2 and of a fluoropolymer were developed. They were applied on a limestone substrate. The obtained coatings were proved able to provide the functionalization of the stone with simultaneous photocatalytic and hydrophobic properties. They showed a high photodegradation activity (?90%), although with different kinetics, depending on the amounts of nanoparticles within the polymer. Hydrophobic effectiveness was also dependent on the TiO2 loads; good hydrophobicity was obtained when they were tuned to proper amounts. The addition of TiO2 to the polymer was found to decrease the color impact of the coatings on the stone surface.