Partially fluorinated acrylic copolymers as coatings for stone protection: characterization and surface properties
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Partially fluorinated acrylic copolymers as coatings for stone protection: characterization and surface properties L. Toniolo1, C. Della Volpe2, M. Brugnara2, T. Poli1 1 CNR Center “Gino Bozza” for the conservation of works of art, Politecnico di Milano, Italy 2 Dept. Materials Engeneering, University of Trento, Italy INTRODUCTION In the last decades the conservation and protection of historical buildings, after the increased atmospheric pollution, became a priority in all industrial countries. The natural stones exposed to a dramatically increased aggressive environment show their durability limits. The necessity to study new protective systems specifically projected to defend the materials according to the peculiar characteristics of each stone substrate. The complex heterogeneity of stone substrates demands an adaptable and efficient shielding strategy in order to satisfy the different protection requirements such as water repellency, permeability, photochemical and thermal stability and transparency. These characteristics, obviously, have to be maintained as long as possible. Such modulated multi-response behaviors can only be attempted with materials based on multifunctional copolymers. Different polymeric materials have been employed as coatings for building materials but these products were always transferred from industrial applications to the conservation of Cultural Heritage without a deep knowledge of their properties and without a real optimization of structures for stone protection. Since 1997 in the framework of the C.N.R. Target Project “Safeguard of Cultural Heritage”, there is a specific research to synthesize and to investigate the performance of new fluorinated acrylic copolymers expressly tailored as protective for building materials [1]. In this paper the protective performances of two new fluorinated acrylic copolymers 1H,1H,2H,2H-perfluorodecyl methacrylate/1,1,1,3,3,3–hexafluoroisopropyl methacrylate/ethyl methacrylate/methyl acrylate (XFDM/HFIM/EM/MA) and 1,1,1,3,3,3–hexafluoroisopropyl methacrylate/ethyl methacrylate/methyl acrylate (HFIM/EM/MA) are evaluated and compared with Paraloid B72, a commercial copolymer ethyl methacrylate/methyl acrylate (EM/MA) and its partially fluorinated homologous 2,2,2-trifluoroethyl methacrylate/methyl acrylate (TFEM/MA). These four copolymers have been tested on two different stone materials: Candoglia marble, a very low open porosity stone (
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