Paraloid(乳胶粘合剂)是一系列丙烯酸树脂的商品名称, 是文物保护领域中最常用的保护材料之一, 主要用于文物的加固、 封护和粘接, 适用文物材质范围非常广泛。 其中以Paraloid B-72最具代表性, 在国内外的文物保护中被大量使用, 相关的应用案例、 性能评价及其老化机理研究都有较多报道, 而Paraloid系列的其他产品却鲜有关注, 在国内应用较少, 老化性能研究尚未开展工作。 该研究系统评价了Paraloid B-72, Paraloid B-44, Paraloid B-48N和Paraloid B-67的光老化性能, 采用红外光谱跟踪紫外辐照3 864 h过程中Paraloid材料分子结构变化, 对光老化机理进行了深入解析和半定量评测。 结果显示, 4种Paraloid系列丙烯酸树脂材料中, B-72老化前后颜色和光泽度均没有发生明显变化, B-48N和B-67老化前后色差较大, B-44光泽度降低最多。 丙烯酸树脂老化过程中高分子材料内部发生断链反应以及一定程度的交联反应, 表现在主要官能团吸收的减弱和羰基指数(CI)的增加。 根据主要官能团吸收峰C=O相对强度的半定量分析结果反映出, B-72的光稳定性最好, B-48N和B-44略优于B-67, 但与B-72相比差距较大。 B-67可能是由于异丁基上的叔氢键能较低, 易吸收光能量后产生自由基氧化反应, 因此耐光老化性最差。 综合评定4种Paraloid系列丙烯酸树脂的光老化性能, B-72在4种材料中光稳定性最好, 其次是B-44和B-48N, 最不适宜作为户外文物保护材料的是B-67。 研究结论有望为一线文物保护工作者在选择Paraloid丙烯酸树脂作为保护材料时提供一定的科学参考。

Paraloid is the trade name of a series of acrylic resins. Paraloid products are one of the most useful materials in cultural relics conservation, which is usually applicable to a wide range of artifacts for consolidation, sealing and bonding. Among these products, Paraloid B-72 is the most representative one, widely used in art conservation at home and abroad. There are many reports on application cases, performance evaluation and aging mechanism research of Paraloid B-72. However, the other Paraloid products are obtained less attention due to limited domestic applications, and the aging performance research has not yet been conducted. This paper systematically evaluated the UV aging performance of Paraloid B-72, Paraloid B-44, Paraloid B-48N and Paraloid B-67. By using infrared spectroscopy to track the molecular structure changes during the 3864 h UV test, the aging mechanisms of these Paraloid products were further discussed and semi-quantitatively characterized. The results show that among the four Paraloid acrylic resins, the color and gloss of B-72 do not change significantly before and after aging test, while B-48N and B-67 color change greatly, and the gloss of B-44 decreased the most. During the aging process, the chain scission reaction and a certain degree of cross-linking reaction occur inside the acrylic resins, which is manifested in the weakening of the absorption of main functional groups and the increase of the carbonyl index (CI). According to the semi-quantitative results of the relative intensity of the main functional group absorption peak C=O, it can be reflected that B-72 has the best photostability. B-48N and B-44 perform slightly better than B-67. B-67 may be due to the low tertiary hydrogen bond energy on the isobutyl group, which is easy to absorb UV spectral energy and produce free radical oxidation reactions. Therefore, B-67 has the worst light aging resistance. In the comprehensive evaluation of the light aging performance of four Paraloid acrylic resins, B-72 has the best light stability, followed by B-44 and B-48N, and B-67 is the least suitable conservation material for outdoor cultural relics. The conclusions of this study are expected to provide some scientific suggestions for the first-line cultural relics conservators when choosing Paraloid acrylic resins as the conservation material.