Preparation, characterization of nano-silica/fluoroacrylate material and the application in stone surface conservation

Novel micron-thick brick cladding of polyfluorosilicone acrylates, a case study of conservation of historic brick wall in Hongcun village

A micron-thick (3–5 μm) and transparent cladding technique based on the environment friendly dimethyl carbonate solution of newly developed polyfluorosilicone acrylates was successfully applied to restore the surface of brick walls of a historic house which has been severely eroded by damp and mildew for more than 300 years in Hongcun village, one of the World Heritage sites in China. The restoration followed the rule of repairing old as old before. The cladding made from the copolymerized polyfluorosilicone acrylate resin, which mainly contained the chain fragments of dodecafluoroheptyl methacrylate and 3-(trimethoxysilyl)propyl methacrylate, permeated through the surface of old brick with an average depth of 14.5 mm in this case study, and provided an ultrathin and efficient covering of the microstructure of the shallow surface layer of old bricks and resulted excellent water-proof, moisture-proof, mildew-proof and long-lasting weather resistance effects. The water contact angle of the treated surface of the old bricks reached 133°, the water absorption of treated bricks was reduced from 16.1 wt% to 2.8 wt% after soaking in water for 24 h.

The cladding made from the polyfluorosilicone acrylate resin provided a covering of the microstructure of the shallow surface layer of old bricks, which makes the treated brick wall waterproof, moisture-proof, mildew-proof and weather resistant.

The Adverse Effects of TiO2 Photocatalycity on Paraloid B72 Hybrid Stone Relics Protective Coating Aging Behaviors under UV Irradiation

The incorporation of photocatalytic nanomaterials into polymer coatings is used to protect stone relics from weathering. However, the photocatalytic nanomaterials might generate excess free radicals to degrade the polymer matrix. In this work, a certain amount of TiO₂ nanoparticles were dispersed into Paraloid B72 and applied onto sandstone relics to explore the adverse effects of TiO₂ nanoparticles on Paraloid B72 under ultraviolet (UV) irradiation. To fulfill this goal, the effects of TiO₂ on pore formation and the structure of Paraloid B72 was studied by scanning electron microscopy (SEM). Moreover, the surface chemical composition, pore structure, surface roughness and surface wettability were explored via Fourier transform infrared (FTIR) spectroscopy, SEM, optical profilometer and water contact angle measurement under UV irradiation. Results showed that the incorporation of TiO₂ nanoparticles prohibited the generation of pores in Paraloid B72 and there were no pores formed when the content of TiO₂ exceeded 0.8 wt%. The water contact angle of origin Paraloid B72 and TiO₂/Paraloid B72 decreased with the prolonging UV irradiation. Moreover, TiO₂ nanoparticles were extracted from the matrix and the pores cannot be detected with the prolonging UV irradiation time under a higher content of TiO₂. These research findings might promote the understanding of using photocatalytic nanomaterials in developing stone relics' protective coating.

Study of TiO2-Modified Sol Coating Material in the Protection of Stone-Built Cultural Heritage

Coating materials can effectively protect stone-built cultural heritage and, as such, research into coating materials has gained comprehensive attention from researchers. The aim of this work is to prepare a TiO2-modified sol coating material (TSCM) and study its protective effects on stone-built cultural heritage. TSCM and pure TiO2 sol (p-sol, unmodified; for comparison) were applied evenly over the entire surface of stone samples. The prepared stone samples included untreated stone, stone treated with pure sol, and stone treated with TSCM. The protective effects of TSCM were evaluated by water absorption, water vapor permeability, acid resistance, and weather resistance experiments. The results show that stone treated with TSCM has excellent water absorption and water vapor permeability, strong acid resistance, and good weather resistance, compared with untreated stone or stone treated with p-sol. The acid resistance of stone treated by TSCM was 1.75 times higher than that treated with traditional coating materials. The weather resistance cycle number of stone treated by TSCM was four times higher than that treated with organic protective materials. These findings are expected to provide useful suggestions for the protection of stone-built cultural heritage.