Aging Mechanism and Performance of Paraloid B72 under Simulated UV-Condensation Environment: Insights for Cultural Heritage Conservation

Paraloid B72, a polymer widely applied in cultural heritage conservation, shows specific aging behavior under Sichuan’s simulated UV-condensation conditions. The aging behavior and property changes of B72 during the aging process were analyzed through various characterization techniques including ATR-FTIR, 1H NMR, GPC, TGA, DSC, SEM, tensile testing, color difference analysis, and contact angle measurement. The results indicate that the aging mechanism of B72 under the combined influence of UV and humidity is complex, featuring a synergistic positive feedback cycle where water penetration drives stress-induced chain scission, chain scission causes surface cracking, and cracking promotes further water penetration. A distinct inflection point in the aging progression was observed at 15 days. Before 15 days, water molecules primarily accumulated through penetration, with slight side-chain scission occurring, and the structure and molecular weight remained essentially stable. After 15 days, the scission of C-C bonds between the main chain α-carbon and adjacent carbons, as well as the cleavage of side-chain ester groups, intensified significantly, leading to a marked increase in the degradation rate. This study provides scientific data to support the evaluation of B72's applicability and service life in cultural heritage conservation.