A Durable Nano-SiO2-TiO2/Dodecyltrimethoxysilane Superhydrophobic Coating for Stone Protection

Abstract

Water can trigger freeze–thaw cycles, acid rain corrosion, and microbial colonisation, all of which destroy stone. Water is one of the most influential factors in the destruction of outdoor stone heritage. Therefore, materials with excellent hydrophobic properties and durability are urgently required to effectively retard long-term stone weathering. In this study, two nanoparticles, TiO2 and SiO2, were used to modify dodecyltrimethoxysilane (DTMS), a waterproof coating commonly used for stone heritage protection, to fabricate nanocomposite superhydrophobic coatings. The micromorphology, water repellence (water contact angle and capillary water absorption), suitability to protect stone heritage (color change and water vapor permeability), and durability (thermal, light, and chemical stability) of DTMS and nanocomposite coatings were evaluated. The scanning electron microscope (SEM) images revealed that adding 0.5% (w/w) SiO2 produced nanoscale roughness on the sandstone surface, leading to superhydrophobicity. The results of ultraviolet -visible (UV–Vis) spectrophotometer showed that adding 0.01% TiO2 shielded more than 90% of UV light but accelerated the decrease in the contact angle under UVA irradiation. The addition of SiO2 was able to avoid the detrimental effect of TiO2 under UV light. The thermogravimetric analysis (TGA) results showed that both SiO2 and TiO2 nanoparticles improved the thermal stability of the coatings. In particular, the fabricated nanocomposite coating, SiO2 and TiO2 co-modified DTMS, had excellent water repellence, low color change and outstanding durability, and retained about 85% of the water vapor permeability of the stone, showing promise for stone protection.

Highly Stable Self-Cleaning Paints Based on Waste-Valorized PNC-Doped TiO2 Nanoparticles

“…Possibly, TiO 2 -NPs degrade siloxanes rather than MV upon sunlight exposure. 99 The natural sunlight photocatalytic activity of all MPs remained unchanged for a repeated cycle, which can be seen in Supporting Figure S13 . In T3-, T5-, and P25-MPs, the rate of discoloration was progressive, reaching ≈82% ± 2 after 6 h. Once again, T7-MP was best with more robust discoloration in the first 3 h (89% ± 2) and steady and progressive discoloration between 3 and 6 h (93% ± 2).…”

“…In contrast, SOL-65, which adsorbed the maximum of MV (Figure d), failed to continue photocatalysis after 1 h (67% ± 2), which may be due to the larger particle size (≤150 μm) and titania agglomeration with siloxane resin reducing the active surface (see Figure S12). Possibly, TiO 2 -NPs degrade siloxanes rather than MV upon sunlight exposure . The natural sunlight photocatalytic activity of all MPs remained unchanged for a repeated cycle, which can be seen in Supporting Figure S13.…”

Recent Advances in the Application of Metal Oxide Nanomaterials for the Conservation of Stone Artefacts, Ecotoxicological Impact and Preventive Measures

“…For this, researchers have suggested preparing nanocomposite coatings obtained from nanoparticles combined with organic coatings, with the nanoparticles offering a rough structure and the organic component providing small surface energy. In this context, Peng et al ( 2022) [123] elaborated nanocomposite superhydrophobic coatings composed of silicon dioxide and titanium dioxide NPs, which were used to modify a waterproof coating obtained from dodecyltrimethoxysilane (DTMS). DTMS is utilized for many applications, such as fabric waterproofing, alloy anticorrosion, and notably, sandstone protection [123]; however, reports have declared that DTMS has weak resistance to light and low durability.…”

“…In this context, Peng et al ( 2022) [123] elaborated nanocomposite superhydrophobic coatings composed of silicon dioxide and titanium dioxide NPs, which were used to modify a waterproof coating obtained from dodecyltrimethoxysilane (DTMS). DTMS is utilized for many applications, such as fabric waterproofing, alloy anticorrosion, and notably, sandstone protection [123]; however, reports have declared that DTMS has weak resistance to light and low durability. It is expected that the introduction of NPs into the structure of organic coatings will be able to enhance features such as substrate adherence, thermomechanical characteristics, chemical stability, resilience to wear, self-cleaning, and notably, resistance against UV light degradation, which would extend the durability and the hydrophobic character of DTMS.…”

Preparation and Characterization of Biomimetic SiO2-TiO2-PDMS Composite Hydrophobic Coating with Self-Cleaning Properties for Wall Protection Applications

“…However, the above-mentioned preparation processes are complex, and the required equipment is demanding, which limits the large-scale preparation and application of the coatings [20]. Due to the advantages of a simple operation and easy control of reaction conditions [21,22], the sol-gel method has been widely used for the preparation of superhydrophobic coatings on wood and stone surfaces [23][24][25][26]. Zhou H et al [27,28] modified silica sol with 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane and prepared aqueous superhydrophobic coatings on the surface of substrates such as glass, fibers, and wood.…”