有机硅橡胶在出土象牙封存中的老化结构研究

doi:10.3964/j.issn.1000-0593(2025)06-1592-06

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摘要：为防止金沙遗址出土象牙因快速失水而发生开裂、粉化和剥落等病变，一种室温固化、锁水保湿、耐候性良好、无色透明、易剥离的有机硅橡胶被用于出土象牙的临时封存保护。但封存二十年后，有机硅橡胶出现了雾化发白和不透明的现象，对象牙封存效果产生了影响。采用傅利叶红外光谱（FTIR）和固态核磁硅谱（²⁹Si NMR）等分别对有机硅橡胶老化前后的特征官能团和特征元素组成进行光谱分析；通过热失重分析（TGA）检测有机硅橡胶老化前后热稳定性；运用热重-红外联用分析(TG-FTIR)进一步分析有机硅橡胶老化前后样品在受热过程中所发生的物理-化学变化；采用扫描电子显微镜（SEM）和白度计明确有机硅橡胶的形貌和透明度变化。结果表明，有机硅橡胶中在长期的封存环境中发生局部的环氧基与羟基的交联、硅羟基的缩合反应，老化有机硅橡胶的局部交联度增加，残留率增加。TG-FTIR分析结果显示，老化前的有机硅橡胶在热分解过程中产生了CO₂，NH₃和H₂O，而老化后的热分解产物为CO₂和H₂O，进一步证实老化前有机硅体系中存在硅甲基、羟基、硅羟基和氨基。当温度升高至500 ℃后，聚硅氧烷发生了热解聚反应，产生小分子六甲基环三硅氧烷。老化有机硅橡胶增加的交联位点是薄弱区，使体系内出现应力集中中心，产生微裂纹，造成材料光折射率的改变，使硅橡胶的透明度从98%降至89%，因此，有机硅橡胶出现发白现象。通过对象牙封存用有机硅的老化结构与性能分析，明确了有机硅橡胶雾化发白的机理。该研究的开展为象牙封存材料的改进提供了数据支撑，有助于提升出土象牙的保护科技水平。

关键词：象牙封存用有机硅橡胶；光谱分析；热分析；老化机理

Abstract：To protect the ancient ivory at the Jinsha site from cracking, deformation, and pulverization due to rapid dehydration, a type of silicone rubber with room-temperature curing, water-locking, and moisturizing properties, as well as good weather resistance, colorlessness, transparency, and easy peeling, was used as the temporary sealing material for unearthed ivory. However, the colorless, transparent silicone rubber turned into a white, opaque rubber after twenty years of storage, which was detrimental to the storage of ivory. In this paper, Fourier transform infrared spectroscopy (FT-IR) and solid-state nuclear magnetic resonance spectroscopy (²⁹Si NMR) were used to analyze the composition of functional groups and characteristic elements of silicone rubber before and after aging. Thermogravimetric analysis (TGA) was carried out to investigate the thermal behavior and thermal stability of silicone rubber before and after aging. Thermogravimetric-infrared analysis (TG-FTIR) was employed to investigate the physical and chemical changes of silicone rubber samples before and after aging. A scanning electron microscope (SEM) and a whiteness meter were used to determine the differences in structure and transparency of silicone rubber before and after aging. The results showed that the cross-linking reaction between the epoxy group and the hydroxyl group, as well as the condensation reaction of the silicon hydroxyl group, occurred in silicone rubber under long-term storage conditions. With the increase in the degree of cross-linking, the residual ratio also improved correspondingly. According to TG-FTIR analysis, CO₂, NH₃, and H₂O were produced during the thermal decomposition process of the silicone rubber before aging. In contrast, the thermal decomposition products after aging were CO₂ and H₂O, which further confirmed the presence of silicomethyl, hydroxyl, silicomethyl, and amino groups in the silicone system. When the temperature was raised to 500 ℃, hexamethylcyclotrisiloxane was produced due to thermal depolymerization of polysiloxane. The cross-linking sites of aging silicone rubber were weak areas, which ledto stress concentration centers and microcracks in the system, changing the refractive index of the silicone. Consequently, whitish parts were observed in the silicone rubber. According to the aging structure and performance analysis of silicone for unearthed ivory storage, the mechanism of the whitening of silicone rubber was revealed. This project provides data support for the improvement of ivory storage materials, which is beneficial in enhancing the conservation level of cultural relics.

Key words：Silicone rubber for ivory storage; Spectrum analysis; Thermal analysis; Aging mechanism

收稿日期: 2024-09-27 修订日期: 2024-12-26

中图分类号:

O657

基金资助: 国家自然科学基金项目（52303128）资助

通讯作者: 宋永娇，赵丽娟 E-mail: yjsong20170064@sicnu.edu.cn；lijuan_zhao@sicnu.edu.cn

作者简介: 王宁，女，1980年生，成都市文物考古工作队（成都文物考古研究院）研究馆员 e-mail: 25558383@qq.com

引用本文:

王宁，肖嶙，白玉龙，孙杰，蒋璐蔓，李娜，骆光兵，宋永娇，杨弢，赵丽娟. 有机硅橡胶在出土象牙封存中的老化结构研究[J]. 光谱学与光谱分析, 2025, 45(06): 1592-1597.
WANG Ning, XIAO Lin, BAI Yu-long, SUN Jie, JIANG Lu-man, LI Na, LUO Guang-bing, SONG Yong-jiao, YANG Tao, ZHAO Li-juan. Research on the Aging Structure of Silicone for Unearthed Ivory Storage. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2025, 45(06): 1592-1597.

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