Transparent and superhydrophobic coating via one-step spraying for cultural relic protection against water and moisture

Paraloid B72, composed of an ethyl methacrylate (70%) and methyl acrylate (30%) copolymer, is widely used in the field of cultural relics protection due to its transparency, durability, and nonyellowing. However, B72 is hydrophilic and the water resistance should be enhanced. Herein, as a further study of the pioneer research by Ntelia et al. [1], transparent superhydrophobic coating was prepared and the durability as well as the protection against moisture will be studied. B72 was mixed with the hydrophobic nanoparticles of SiO2 in xylene and a transparent and superhydrophobic coating was then obtained by spraying onto the substrate of fabric, paper and wood. The fraction of SiO2 in the mixture was optimized to be 2 wt% by taking hydrophobicity, air permeability, transparency, and ultraviolet transmittance into consideration. The optimal coating presented a continuous porous network surface structure with the maximum contact angle of 165 degrees and the minimum sliding angle of 6 degrees. Average transmittance in visible and ultraviolet light range for the composite coating on glass was 72.57% and 19.46%, versus 82.81% and 32.26% for B72, respectively. BS2 coating permeability for different substrates are less than 10%. Contact angle remained above 150 degrees after 4 h of contact with liquids with a pH of 1-13. Water contact angle on the simulated paper relics after exposure to a hot humid (60 degrees C, 85 - 90 RH%) atmosphere for 5 days remained above 150 degrees. In addition, BS2 coating showed good UV resistance after 10 days of UV light irradiation. All these data demonstrated that such a coating may find potential application in the relic protection due to its superhydrophobicity, breathability, transparency, ultraviolet protection, and durability.

Automated summary

This study prepared a transparent superhydrophobic coating by mixing B72 with hydrophobic nanoparticles of SiO2 and spraying onto substrates such as fabric, paper, and wood. The optimized coating demonstrated a continuous porous surface structure with a maximum contact angle of 165 degrees and a minimum sliding angle of 6 degrees. The composite coating showed lower transmittance in visible and ultraviolet light compared to B72, but had improved water resistance, pH resistance, and UV resistance. It may find potential applications in relic protection due to its superhydrophobicity, breathability, transparency, ultraviolet protection, and durability.