Application of Polyvinyl Alcohol–Ethylene Glycol Hydrogel Technology for Removing Animal Glue in Book Restoration Based on Fluorescent Labeling Evaluation

This study developed a novel material based on polyvinyl alcohol-ethylene glycol (PVA-EG) hydrogel and systematically evaluated its potential application in the removal of animal glue from book surfaces. The microstructure, surface properties, and mechanical characteristics of the PVA-EG hydrogel were analyzed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), contact angle measurements, a universal testing machine, and a dynamic mechanical analysis (DMA). The introduction of ethylene glycol (EG) could weaken hydrogen bonding interactions between PVA chains to enhance the molecular chain flexibility of the hydrogel. Notably, the 10% PVA-EG hydrogel shows better crystallinity, higher hydrophilicity, and optimal balance between mechanical strength and flexibility compared to pure PVA, which is conducive to improving the efficiency of the removal of animal glue. Additionally, the effectiveness of the process of removing animal glue was verified by real-time monitoring using europium nitrate at a concentration of 0.4% (w/v) as a fluorescent marker. Such hydrogels with high mechanical properties, strong surface hydrophilicity, good removal efficiency, and gentle treatment characteristics have potential applications in the restoration of cultural heritage.