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.

This paper aims to study the effect of a hindered amine light stabilizer (HALS 770), on the aging behavior of moisture-curable polyurethane (MCPU). MCPU is specifically developed by ourselves for the reinforcement of fragile organic cultural relics in high-humidity environments, but its aging resistance is insufficient. To improve the aging resistance of MCPU, HALS 770 was used to prepare a modified MCPU (MMCPU). A colorimeter, an infrared spectrometer and a thermal analyzer were used to characterize the color and structure changes of MCPU and MMCPU during aging and to determine their aging kinetics. The results show that the activation energy for the thermal decomposition increased from 91-109 kJ/mol to 135-151 kJ/mol. When the color change is used as the indicator for aging, the lifetime of MMCPU under UV aging is 133% longer than that of MCPU, the lifetime of MMCPU under thermal aging at 293 K is 41.3 times that of MCPU. The addition of HALS 770 to MCPU significantly inhibits the aging behavior.

Moisture-curable polyurethane (MCPU) is a specifically designed material for the consolidation of fragile cultural objects in high-humidity environments. In order to solve the problem of its susceptibility to yellowing due to heat ageing, polyhedral oligomeric silsesquioxane (POSS) was added to the MCPU to prepare POSS/MCPU. The appearance, stability and mechanical properties of the POSS/MCPU films were characterized using a UV–Vis spectrophotometer, a gloss meter, a colorimeter, a thermal analyzer and a universal material testing machine. The results showed that the films are colorless and transparent and have a light transmission of over 80%. The addition of POSS has almost no effect on the chromaticity of the MCPU, while the thermal stability of the POSS/MCPU is improved compared to the pristine MCPU. The modified film is 2.50 times more resistant to yellowing by heat. The addition of POSS also simultaneously enhances the strength and toughness of the film. Using POSS/MCPU to reinforce the fragile object, the material was found to be significantly effective, indicating it has the potential to be used during the extraction of fragile cultural objects from archaeological sites.

Several well-preserved polychrome lacquered coffins were found in Zhang Dong family’s tombs in Shaanxi, China, rare in the history of archaeological excavation. In the lacquered coffins, a large amount of dark solid of suspected natural resin was unearthed with mysterious compositions and uses, exerting a tremendous fascination on archaeologists. In this work, a new method was explored for the identification of the suspected natural resin, mainly based on thermogravimetry (TG), elemental analysis (EA), scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF-MS) and Fourier transform infrared spectrometry (FT-IR). The results suggested that the sample was mainly composed of organics with a content of 81.66% and little inorganics with a content of 2.21% by water excluded. Rosin with the main component of abietic acid (molecular formula C20H30O2) was identified as the principal component of the sample. Dehydrogenated abietic acid (DHA) and other oxides were also tested out. FT-IR confirmed the identification results. SEM revealed the rough surfaces evenly covered with holes of similar sizes. The use of this method directly obtained integral quasi-molecular ion fragments and molecular components of the sample. As a result, intricate multi-stage mass spectrometry is avoidable, which dramatically simplifies the analysis procedure. This approach is simple and effective for the identification of precious relic samples, requires no references, and has potential for the analysis of these kinds of unknown samples. Especially, for the first time, EA is used to identify natural resins from archaeological sites.