Effects of UV Light on the Structure and Properties of Glyoxal Polymers

ABSTRACT Glyoxal dehydration and reinforcement are among the most widely used methods for treating water‐saturated wood lacquerware in China. Ultraviolet (UV) light has a significant impact on the structure and properties of glyoxal polymers, which in turn can affect cultural relics treated with the glyoxal method. Therefore, in this study, a degradation experiment of glyoxal polymer was carried out under UV light irradiation at a wavelength of 351 nm. Fourier transform infrared spectroscopy, scanning electron microscopy, and differential scanning calorimetry were then performed on the samples after the test. Characterization tests, including calorimetry, were used to evaluate the effect of UV light on glyoxal polymers. After UV light irradiation, the surface color of the glyoxal polymer first brightens, then gradually darkens. The surface appears convex or even cracked; the overall shape gradually expands, and the volume increases significantly, but the mass gradually decreases. The analysis results show that after UV light irradiation, the glyoxal polymer chain breaks down, the glass transition phenomenon gradually disappears, and the decomposition temperature decreases. Photoaging occurs on the surface of the glyoxal polymer, leading to the formation of carbonyl groups (C=O) and an increase in cyano groups (–C≡N).