Hydrophobic photopolymerizable nanostructured hybrid materials: An effective solution for the protection of porous stones

In order to guarantee a very high preservation of stone artworks from water actions, an experimental superhydrophobic photopolymerizable organic-inorganic (O-I) nanostructured hybrid product, namely HEP, has been developed and tested on a calcarenitic stone characteristic of Apulia Region (Italy), i.e., Pietra Leccese (PL). HEP is a green product, not containing harmful solvents, and is able to quickly set and harden at room temperature. The first part of the work was devoted to the analysis of the dimension of the silica nanodomains and the suitability of the liquid system produced to be applied on stone surfaces. To this aim, dynamic light scattering and rheological analyses were performed after different times from the preparation of the O-I system. The hybrid mixture was subsequently applied on a glass substrate and photopolymerized by UV lamp. Several physical properties (glass transition temperature, transparency, scratch, and surface hardness) were, then, measured on the hybrid coating: a substantial improvement of all the surface properties measured was observed. HEP was, finally, applied on PL elements and different analytical techniques (contact angle, colorimetric and water absorption measurements, liquid water, and vapor water transmission) were used to fully characterize the product in terms of hydrophobicity, protective efficacy, water penetration resistance, and transpiring capability. The protective properties of the novel hybrid coating were also compared with those of two commercial water-repellent products, applied on the same stone substrate, evidencing that the experimental coating is able to equal the performance of high-quality commercial products. POLYM. COMPOS., 36:1039-1047, 2015. (c) 2015 Society of Plastics Engineers