Study on aging behavior of polyethylene glycol under three wavelengths of ultraviolet light irradiation

<title>Abstract</title> Polyethylene glycol (PEG2000) is commonly used for the dehydration and reinforcement of waterlogged wooden cultural relics, and its photo-aging degradation will seriously affect the long-term conservation of the wooden cultural relics. In this study, the photo-aging characteristics and mechanisms of PEG2000 under UV irradiations of three wavelength were comprehensively investigated, and the surface morphology, crystal structure, and relative molecular weight of PEG2000 were systematically characterized. The results showed that PEG2000 showed a higher gloss loss rate, carbonyl index and crystallinity, and a wider molecular weight distribution with increasing aging time, especially under the irradiation of 313nm ultraviolet light. The aging mechanism of PEG2000 was proposed based on FTIR and ¹H NMR analyses, and it was found that the degradation occurred at the C-H and ether (C-O-C) bonds on the main chain, forming a large number of ester and ethoxy structures. The aging degree of PEG2000 was evaluated from the perspective of surface morphology and chemical structure by gloss and FTIR spectroscopy, and it was found that the combination of gloss loss rate and carbonyl index was more suitable to evaluate the aging degree of the sample. The relevant theoretical research will provide reliable guidance for the preservation of polyethylene glycol in waterlogged wooden cultural relics.