Surface properties of super-hydrophobic coatings for stone protection

Abstract

Superhydrophobic films are produced by a simple and low cost method. Silica (SiO2) nanoparticles are dispersed in solutions of Rhodorsil 224, a commercial poly (alkyl siloxane) which is used for the protection of outdoor cultural heritage objects, and the suspensions are sprayed on glass surfaces. It is shown that the siloxane-nanoparticle composite films prepared from dispersions of high particle concentrations (≥ 0.5% w/v) exhibit superydrophobic properties (high static contact angle and small hysteresis) which can be rationalized by the Cassie-Baxter model, according to quantitative measurements obtained by SEM images. Siloxane-nanoparticle films are then deposited (sprayed) on “Opuka”, a fine-grained argillite which was used for the restoration of the castle of Prague. It is shown that the treated stone surfaces exhibit superydrophobic properties, similar to the treated glass surfaces.