Calcitic-based stones protection by a low-fluorine modified methacrylic coating

Abstract

Atmospheric pollutants, such as NOx, SO2, and particulate matter, together with water percolation inside the stone pores, represent the main causes of cultural heritage decay. In order to avoid these undesired phenomena, the application of protective coatings represents a reliable solution. In this context, the present study focused on the synthesis of low-fluorine content methacrylic-based (MMA) polymeric resins characterized by seven F atoms (namely F7 monomer) in the lateral chains. Four different percentages (1.0, 2.5, 5.0, and 10.0%) of the present monomer were adopted to obtain a final polymeric structure showing the desired hydrophobicity, processability, and structural and thermal stability (even after accelerated UV aging tests). MMA_F7(1.0) seemed to be the optimal one; therefore, it was further applied onto Candoglia marble. Specifically, the treated substrates showed good surface hydrophobicity, water repellency, and water vapor transpirability. No color variation was observed even after a 1.5-year exposure in a real polluted environment (Monza Cathedral). Interestingly, the application of this coating hindered the atmospheric nitrates penetration inside the stones and, at the same time, it limited the sulfates (gypsum) formation, thus revealing a very promising marbles protection resin.

Performance evaluation of a commercial protective coating through field-exposure tests on three stone substrates

“…In the field of cultural heritage, protective coatings play a key role in the preservation of monuments, statues, and many other works of historic and artistic interest. These treatments are necessary [1]- [6] in order to prevent the development of numerous possible degradation phenomena, such as the formation of black crusts, chromatic alterations, detachment of the substrate, erosion, and many other effects [7]- [10]. The main factors which give rise to these processes are: the interaction between the substrate and air pollutants (sulphur dioxide, particulate matter, and nitrous oxides), the crystallization of soluble salts, and biodeterioration [1], [11], [12].…”

“…These treatments are necessary [1]- [6] in order to prevent the development of numerous possible degradation phenomena, such as the formation of black crusts, chromatic alterations, detachment of the substrate, erosion, and many other effects [7]- [10]. The main factors which give rise to these processes are: the interaction between the substrate and air pollutants (sulphur dioxide, particulate matter, and nitrous oxides), the crystallization of soluble salts, and biodeterioration [1], [11], [12]. Stone materials are amongst the substrates which mostly suffer from the degradation phenomena and for this reason they have been, and still are, at the centre of attention in this field [13].…”

Application of a polymer-based photocatalytic coating for the protection of limestone stones substrates: an exposure study

“…In the field of cultural heritage, protective coatings play a key role in the preservation of monuments, statues and many other works of historic and artistic interest. These treatments are necessary [1][2][3][4][5][6] in order to prevent the development of numerous possible degradation phenomena, such as the formation of black crusts, chromatic alterations, detachment of the substrate, erosion and many other effects [7][8][9][10]. The main factors which give rise to these processes are: the interaction between the substrate and air pollutants (sulphur dioxide, particulate matter and nitrous oxides), the crystallization of soluble salts and biodeterioration [1].…”

“…These treatments are necessary [1][2][3][4][5][6] in order to prevent the development of numerous possible degradation phenomena, such as the formation of black crusts, chromatic alterations, detachment of the substrate, erosion and many other effects [7][8][9][10]. The main factors which give rise to these processes are: the interaction between the substrate and air pollutants (sulphur dioxide, particulate matter and nitrous oxides), the crystallization of soluble salts and biodeterioration [1]. Stone materials are amongst the substrates, which mostly suffer from the aforementioned degradation phenomena and for this reason they have been, and still are, at the centre of attention in this field [11].…”

“…In fact, many products now used in conservation, such as composite based polymeric materials, were studied and tested in various research areas and then readapted to the need of the Cultural Heritage sector. So, applying them to Cultural Heritage requires extensive analytical research useful to assess their potentialities and possible risks [1][2][3][4][5][6].…”