Effect of solvent type on polycondensation of TEOS catalyzed by DBTL as used for stone consolidation

Salazar-Hernández, Carmen; Zárraga, Ramón; Alonso, Sergio; Sugita, S.; Calixto, Sergio; Cervantes, Jorge

doi:10.1007/s10971-008-1879-9

Cited by 46 publications

(22 citation statements)

References 18 publications

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“…Hence, TEOS efficacy confirmed to be highly dependent on the solvent type [13]; when isopropyl alcohol is used, TEOS performances are comparable to those of HAP, while the formulation in white spirit leads to better mechanical performances.…”

Section: Resultsmentioning

confidence: 91%

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Consolidation of porous carbonate stones by an innovative phosphate treatment: mechanical strengthening and physical-microstructural compatibility in comparison with TEOS-based treatments

2015

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For preservation of stones used in Cultural Heritage, affected by weathering processes that threaten their cohesion and mechanical properties, the application of consolidants is a common practice. However, available consolidating products generally exhibit some drawbacks that hinder their performance, in terms of either mechanical efficacy, compatibility with the substrate and/or durability. Ethyl silicate is currently the most widely used among stone consolidants; nevertheless, its reduced efficacy on calcitic substrates, together with its temporary hydrophobicity, its tendency to crack and its common formulation with volatile organic solvent, make the research for alternative consolidants for carbonate stones necessary. In this paper, a recently proposed new consolidation treatment based on the formation of hydroxyapatite inside the stone was tested on two different porous carbonate stones (Globigerina Limestone and Giallo Terra di Siena), and compared with TEOS-based treatments, frequently used for the consolidation of these lithotypes. The results show that the hydroxyapatite treatment exhibits a good efficacy in terms of mechanical properties and, compared to TEOS, it causes less pronounced alterations in open porosity and water transport properties. This makes the new treatment a potentially valid alternative to TEOS, especially in those situations where the possible presence of water behind the consolidated layer (e.g. in case of rising damp, condensation or infiltration) might threaten the durability of the consolidation intervention.

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Section: Resultsmentioning

confidence: 91%

“…Solvent evaporation and gel syneresis (i.e. contraction due to condensation occurring between unreacted groups in the network [12]) during curing directly affect gel tendency to crack [13].…”

Section: Introductionmentioning

confidence: 99%

Consolidation of porous carbonate stones by an innovative phosphate treatment: mechanical strengthening and physical-microstructural compatibility in comparison with TEOS-based treatments

2015

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“…The colloidal silica used for the preparation of hybrid materials was obtained by a variation of the Stöber method (SiO 2 ‐ST), as was previously reported 27. TEOS (Fluka, 98% purity) was used to prepare TEOS sols with different amounts of colloidal silica.…”

Section: Methodsmentioning

confidence: 99%

“…In a recent study, we reported the effect of aprotic and protic solvents on TEOS‐xerogel properties when DBTL is used as polycondensation catalyst,27 and on the TEOS‐DBTL gelation process 28. We suggested that TEOS xerogel properties are improved when a mixture of methylethyl ketone (MEK) and ethanol are used as solvents.…”

Section: Introductionmentioning

confidence: 99%

TEOS–colloidal silica–PDMS‐OH hybrid formulation used for stone consolidation

Salazar-Hernández

Puy-Alquiza

Salgado

et al. 2010

Applied Organom Chemis

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The consolidation of materials concept, which consists of introducing a chemical substance (consolidant) into degraded stone, has been applied to architectural conservation. Silicon compounds such as tetraethoxysilane (TEOS) are frequently used as a base for commercial consolidant formulations due to their ability to form a siloxane polymer such as SiO 2 . However, the silica xerogels deposited into the stone show poor performance and the gels obtained are non-porous and tend to crack during the drying stage. In order to avoid the fractures and to improve gel properties, we propose the synthesis of a hybrid consolidant based on TEOS and fillers such as colloidal silica (200 nm in diameter) and hydroxy-terminated polydimethylsiloxane (PDMS-OH). Both additives enhance gel properties such as porosity and elasticity, leading to the formation of non-fractured and permeable gels. Characterization of the hybrid xerogel was carried out by nitrogen adsorption and 29 Si MAS-NMR. The properties of the hybrid xerogels were compared with those prepared from a formulation based on TEOS (T-ME) with a composition similar to a commercial product. In order to evaluate the effectiveness of the hybrid consolidant, it was applied to tuff-stone of historical monuments in the city of Guanajuato, Mexico. The tuff-stone was also treated with the formulation T-ME. Both treatments were studied by determining the percentage of consolidant deposited, evaluating changes in porosity and hardness of the treated stone. The applicability of the hybrid consolidant for the decayed tuff-stone is under study.

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“…Polymerization of TEOS using DBTL is reasonably well established . A neutral catalyst such as DBTL undergoes hydrolysis reactions as depicted in Scheme , Eqn , to form a tin‐hydroxyl intermediate as the active species [R].…”

Section: Resultsmentioning

confidence: 99%

Highly transparent flexible polydimethylsiloxane films – a promising candidate for optoelectronic devices

Sundar

Raja

Sanjeeviraja

et al. 2016

Polymer International

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In the present work, a siloxane based flexible substrate for optoelectronic applications with improved flexibility and high temperature withstanding capacity has been fabricated and the details are reported. The structural and optical properties of the substrate were characterized and the optical transparency is found to be about 90% − 95% in the visible region. The substrate withstands temperatures up to 300 °C without significant degradation and has a low thermal coefficient of expansion. Fourier transform infrared spectral data show the materials in the prepared substrate and SEM studies show the surface and cross‐sectional characteristics of the substrate. It has good mechanical strength, can withstand a high breaking load of 7 N, has a average tensile strength of 48.86 MPa and high average tensile modulus of 127.32 and also possesses excellent surface smoothness and resistance to both chemical and moisture with better rigidity; it will be a long lasting alternative for flexible plastic substrates. The optical characteristics such as refractive index (n) and extinction coefficient (k) are also reported. © 2016 Society of Chemical Industry

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Effect of solvent type on polycondensation of TEOS catalyzed by DBTL as used for stone consolidation

Cited by 46 publications

References 18 publications

Consolidation of porous carbonate stones by an innovative phosphate treatment: mechanical strengthening and physical-microstructural compatibility in comparison with TEOS-based treatments

Consolidation of porous carbonate stones by an innovative phosphate treatment: mechanical strengthening and physical-microstructural compatibility in comparison with TEOS-based treatments

TEOS–colloidal silica–PDMS‐OH hybrid formulation used for stone consolidation

Highly transparent flexible polydimethylsiloxane films – a promising candidate for optoelectronic devices

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