Novel hydrophobic free-solvent UV-cured hybrid organic–inorganic methacrylic-based coatings for porous stones

The application of hydrophobic polymers to stone materials is an effective way to preserve stone artifacts and protect Cultural Heritage from decay. To improve the characteristics and performance of waterrepellent treatments, and to avoid the use of harmful solvents, new solutions have been recently explored. The authors have recently proposed experimental photopolymerizable hybrid organic–inorganic (O–I) protective coatings, mainly intended for the surface protection of porous stones. In this paper, different analytical techniques (contact angle, colorimetric measurements, water absorption measurements, ESEM–EDS analyses) were employed to fully characterize the innovative water-repellent coatings applied on a calcareous stone substrate, typical of Apulia Region (Pietra Leccese, PL). The research work consists of two parts: the first one concerns the evaluation of the appropriate amount of the novel photopolymerizable O–I hybrid coating applied on Lecesse Stone in order to achieve better protective properties; the second one refers to the comparison of the properties of this latter coating with two commercial waterrepellent products. The final performances of the innovative free-solvent photopolymerizable coating, in terms of hydrophobicity and color change, are found to be comparable to those of the commercial products.