Polymer-Silica nanoparticles composite films as protective coatings for stone-based monuments
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IOP Publishing doi:10.1088/1742-6596/61/1/269
Journal of Physics: Conference Series 61 (2007) 1361–1365 International Conference on Nanoscience and Technology (ICN&T 2006)
Polymer-Silicananoparticles composite films as protective coatings for stone-based monuments
P Manoudis1, S Papadopoulou1, I Karapanagiotis2, A Tsakalof3, I Zuburtikudis4 and C Panayiotou1 Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece 2 “Ormylia” Art Diagnosis Centre, Ormylia, Chalkidiki, 63071, Greece 3 Medical Department, University of Thessaly, Larissa, 41222,Greece 4 Department of Industrial Design Engineering, TEI of Western Macedonia, Kozani, 50100, Greece E-mail: email@example.com
Abstract. The decrease of surface energy of mineral substrates similar to those used in many stone monuments of cultural heritage by the application of protective polymer coatings along with the simultaneous increase of their surface roughness can increase their abilityto repel water substantially. In this work, the effect of artificially induced roughness on the water repellency of mineral substrates coated with protective polymer films was investigated. Natural marble samples or home made calcium carbonate blocks were tried as the mineral substrates. The roughness increase was achieved by mineral chemical etching or by creation of nanoscale binary compositionfilm on the substrate surface. PMMA and PFPE were the polymers used, while different-sized silica nanoparticles were employed for the production of the nanocomposite films. Examination of the coated and uncoated surfaces with profilometry and AFM and measurements of water contact angles reveal a pronounced effect of the surface roughness on water repellency. Especially in the case ofnanocomposite coatings, the surfaces become super-hydrophobic. This result indicates that the nanoscale binary composition film scheme, which is characterized by its simplicity and low cost, is a suitable candidate for the water protection of stone-based monuments on large scale.
1. Introduction Degradation and deterioration of stone-based monuments is caused by many factors among which water action isof predominant importance. Rain water can cause stone degradation by multiple actions comprising stone disintegration by freeze-thaw cycling inside the stone pores or mineral dissolution, especially by environmentally acidified water. It can also be a carrier of pollutants which have their own contribution to the whole phenomenon [1-2]. The protection of stone-based monuments from naturalweathering and/or environmentally-induced accelerated disintegration can be achieved by the application of water-repellent polymer films on the stone surface. Water repellent polymer films have been used extensively during the past decades for the protection of stone monuments, but their protective efficiency strongly depends on the characteristics of the substrate such as roughness and
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porosity . Consequently, developing strategies to enhance the hydrophobicity of these films is important for the effective protection and conservation of monuments of the cultural heritage. As previous studies have pointed out [4-5], hydrophobicity is governed by two parameters: i) the interfacial tension between...