Characterization of a hybrid nano-silica waterborne polyurethane coating for clay bricks

Abstract

A transparent hybrid organic-inorganic waterborne coating is evaluated for the protection of clay bricks. The nanocomposite film was prepared by combining an environmental friendly process based on UV-curing of water based acrylic resins and a mild thermal treatment to form nanosilica in situ from alkoxysilane precursors. Coated and uncoated facing bricks were compared by scanning electron microscopy, surface profilometry, water wettability and capillary rise tests. The hybrid coatings acts as a moderate water repellent: interestingly no appreciable alteration of the aesthetical properties of the brick was observed, in particular no gloss and colour change appeared after the treatment.

Novel Attribute of Organic–Inorganic Hybrid Coatings for Protection and Preservation of Materials (Stone and Wood) Belonging to Cultural Heritage

“…Silicon dioxide nano-particles (from 0.1% to 8%) have been added to polymer based on silanes/siloxanes [37][38][39], fluoropolymers [40,41], polyurethanes [42,43], polyurethane-acrylate [44], methacrylic resins [45,46], unsaturated polyester resin [47], DGEBA-amine epoxy resins [48,49]. In these hybrids, silica nano-particles usually have dimensions around 7-14 nm in mean diameter [37,38].…”

“…The preparation through a sol-gel process is usually carried out via co-condensation of compounds containing -Si(OR)3 moieties (such as tetra-ethyl-orthosilicate (TEOS) [43,45]) and a polymer (polydimethylsiloxane (PDMS) [53][54][55], trimethoxysilyl-propyl methacrylate (TMSPMA) Figure 6. Schematic of four different surface structure types and their wetting behaviors.…”

“…The preparation through a sol-gel process is usually carried out via co-condensation of compounds containing -Si(OR) 3 moieties (such as tetra-ethyl-orthosilicate (TEOS) [43,45]) and a polymer (polydimethylsiloxane (PDMS) [53][54][55], trimethoxysilyl-propyl methacrylate (TMSPMA) [56]), in the presence of a surfactant (n-octylamine [53,54,57], dodecylamine [56]). In the processes where techniques based on two-stages [56], that is sol-gel and free-radical polymerization, have been applied to obtain hybrid nano-composites, the 2,2-azobis(2-methylpropionitrile) (AIBN) and/or acids can be used as additional reagents.…”

“…Because the water contact angle cannot be increased beyond 120 • by a purely chemical process on a smooth surface, the high contact angles (>140 • ) are due to the combined effect of a low surface energy of the polymer and surface roughness [54]. However, in these hybrid materials super-hydrophobicity is not always achieved [53]; this worse behavior is observed where the treatment does not affect surface roughness [43].…”

Studying the efect of nano­liquids on the operational properties of brick building structures

“…In civil construction, a ceramic face brick is widely used as a decorative facade facing [9,10]. At the same time, the physical and technical parameters of the wall material play a decisive role in the regulation of operational properties of the brick structure.…”