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

Abstract

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.

Nanodispersions of TiO2 in Water for Removing Acrylic Films Used in Conservation

“…Negligible variations were instead observed in PB72 samples without TiO 2 nanoparticles after 168 h of exposure. This behavior can be reasonably ascribed to the de-polymerization reactions in the polymer chain promoted by the photo-degradative action of TiO 2 nanoparticles, according to the mechanism proposed by Li W. et al [9]. In line with this interpretation is the overall decrease in intensity of the absorption in the FTIR spectra of Paraloid films treated with the nanodispersion after exposure.…”

“…Recent studies carried out on films of the acrylic polymer Paraloid B72 (a copolymer of methyl acrylate/ethyl methacrylate 30/70 % w/w), containing nanostructured TiO 2 have shown some degradation effects due to photo ageing [8,9]. Acrylic coatings have been used in the field of cultural heritage conservation since 1930 thanks to their ease of removal, transparency, absence of color, and ease of applicability in a thin coating [10].…”

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

“…Compared with D, the UVA resistance of DT was lower. This may have been due to the photocatalytic activity of TiO 2 under UV light, which degraded DTMS under UVA irradiation [51], causing a decrease in its original hydrophobic property. Another explanation is that TiO 2 is photophilic [52] and hydrophilic under UV radiation, adsorbing invisible water films and causing a decrease in the contact angle [53].…”

A Novel Protection Method for Carbonate Stone Artifacts with Gypsum Weathering Crusts

“…Many different kinds of inorganic nanometric reinforcing agents, such as TiO 2 and SiO 2 , were incorporated with organic polymers by scientists who sought better conservation material [15]. Nevertheless, recent results showed that the added TiO 2 nanoparticles can cause the degradation of the incorporated Paraloid B-72 after exposure to UV light for a certain period of time; other outcomes also indicate that the durability of these organicinorganic hybrid materials are not satisfying [16]. Conversely, the inorganic materials show high compatibility with the protected inorganic substrates; thus, leading to high durability.…”