Fluorine-Modified Polyacrylic Coatings for Cultural Heritage Protection

Deterioration phenomena of ancient and modern stone cultural heritage are natural and unrestrainable decay processes mainly arising from water percolation into stone building materials [1]. Thus, the application of hydrophobic coatings to stone surfaces is mandatory to protect them from the deleterious effects of water exposition. Hence, the aim of the present work was to synthesize new polymeric coatings as stone protective with satisfactory water repellency and improved durability, thanks to the combined use of fluorinated and long alkyl chain monomers and without the use of any photo-stabilizers agents. Herein, new types of polymer protectives were prepared via free radical polymerization between either 1H,1H,2H,2H-Perfluoro-octyl-methacrylate (POMA) and methacrylic monomers (methyl, MMA, and n-butyl, nBuMA, methacrylates) [2,3]. Specifically, POMA was synthesized via esterification reaction using methacryloyl chloride and 1H,1H,2H,2H-Perfluoro-1-octanol. The properties of the home-made hydrophobizing polymers in terms of macromolecular structure, molecular weights, thermal features and water repellency were determined. Furthermore, the long-term behavior of these polymers was estimated by means of accelerated aging tests exploiting UV radiations. Their behavior over time was checked via Size Exclusion Chromatography (SEC) by evaluating Mn and D data of aged polymeric samples and by Fourier Transform Infrared (FT-IR) spectroscopy. By evaluating Mn and D data, all the synthesized polymers seem to be unaffected by UV aging. Thus, the present stable resins were applied on both natural (Botticino marble) and artificial (mortar) stone substrates and their wetting properties together with their absorption by capillarity and water vapour permeability were successfully assessed and compared (Figure 1). All the covered substrates show an increase of water contact angle of around 50° and a decrease in water absorption and permeation of about 50% and 20%, respectively. Hence, the use of these polymer resins can be a way to create tailor-made water repellent materials.