Study of silica nanoparticles – polysiloxane hydrophobic treatments for stone-based monument protection |
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| Authors: | Lavinia de Ferri Pier Paolo Lottici Andrea Lorenzi Angelo Montenero Emma Salvioli-Mariani |
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| Institution: | aDipartimento di Scienze della Terra, Università di Modena e Reggio Emilia, Largo S. Eufemia 19, 41121 Modena, Italy;bDipartimento di Fisica, Università di Parma, viale G.P. Usberti 7/a, 43124 Parma, Italy;cDipartimento di Chimica GIAF, Università di Parma, viale G.P. Usberti 17/a, 43124 Parma, Italy;dDipartimento di Scienze della Terra, Università di Parma, viale G.P. Usberti 157/a, 43124 Parma, Italy |
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| Abstract: | The growing interest in the conservation of historic buildings encourages the development of water-repellent materials and methodologies to consolidate and/or protect stones. Recently, particular attention was devoted to composites of inorganic oxides nanoparticles and hybrid siloxane or silicone polymers. Here we present a study on the water repellence of a thin protective coating obtained through sol-gel process starting from Glymo and Dynasylan 40®, and loading the silicate matrix with nano-sized silica particles (Aeroxide LE1® -Degussa-Evonik). The coatings were applied to limestone, sandstone and granite samples. The silica nanoparticles have been characterized by XRD, the siloxane matrix through micro-Raman spectroscopy, while the surface morphology was examined by SEM. The efficacy of the treatments has been evaluated through static contact angle measurements and capillary water absorption. The optical appearance of the coatings was evaluated by colorimetric measurements. Nanoparticles at suitable concentration gave high values for the static contact angle (up to ∼ 150°), for all stone species even for four months exposure to atmospheric conditions. The coatings, in the water capillary absorption tests, however, behave as expected only for granite even if the long-term water direct contact reduces the hydrophobicity. |
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| Keywords: | Stone protection Hydrophobic coatings Silica nanoparticles Sol-gel process |
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