Surfactant-Synthesized Ormosils with Application to Stone Restoration

Abstract

A challenging objective in monumental stone restoration is to synthesize crack-free silica materials for application as consolidants. Hydrophobicity is also a valuable property for such products; it is important to prevent the penetration of water because water is the main vehicle by which the agents of decay enter the pore structure of the stone. We report the development of a hydrophobic crack-free nanomaterial with application to stone restoration. Specifically, organically modified silicate (ormosil) has been synthesized by the co-condensation of tetraethoxysilane (TEOS) and hydroxyl-terminated polydimethylsiloxane (PDMS) in the presence of a nonionic surfactant (n-octylamine). The role played by the surfactant in the assembly of the organic-inorganic hybrid silica gel was investigated. We also prepared a crack-free material using the same synthesis but without adding PDMS to the starting sol. Finally, the effectiveness of the nanomaterials synthesized as a consolidant and hydrophobic protective treatment was evaluated on a particular widely used monumental stone. The high hydrophobicity of the organic-inorganic hybrid product synthesized in our laboratory is discussed as a function of the surface roughness of the material.

Template free preparation of nanoporous organically modified silica thin films on flexible substrates

“…Also, we observed that the hydrophobicity of the paper substrate is stable and there is no significant change in the contact angle even after 25 cycles of bending (bending radius is 2.5 mm). Fig.9b shows the contact angle of the films is stable over the whole pH range (pH [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. There is a slight decrease (6 ) in the contact angle at pH 14 but still the surface is hydrophobic with a contact angle of 117 .…”

New Consolidant-Hydrophobic Treatment by Combining SiO2 Composite and Fluorinated Alkoxysilane: Application on Decayed Biocalcareous Stone from an 18th Century Cathedral

“…The advancing and receding contact angles were measured using the ARCA (Advancing and Receding Contact Angles) method included in the equipment software (OCA 15 plus), with the volume of the droplet being increased/decreased by 5 µL. Details of this procedure are given in a previous paper [10].…”

“…In the last years, we have prepared crack-free nanomaterials for stone conservation [7][8][9][10][11][12][13][14][15][16][17][18]. Specifically, the addition of an aqueous solution of n-octylamine to an alkoxysilane produces inverse micelles, which act as nanoreactors, generating silica seeds.…”

Surface Modification of Sol-Gel Silica Antireflective Coatings by F-PMHS: A Simple Method for Improvement of Amphiphobicity

“…For pure silica xerogel, there are absorption bands observed at around 3450 cm −1 , 2964 cm −1 , 1630 cm −1 , 1090 cm −1 , 954 cm −1 , and 800 cm −1 . The broad absorption band at around 3450 cm −1 is attributed to Si-OH bonds or absorbed water [16,17]. The three peaks around 2964 cm −1 corresponds to the stretching vibration of C-H bonds from -CH3 [18].…”