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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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

Received: 2024-09-27 Accepted: 2024-12-26

ZTFLH:

O657

Corresponding Authors: SONG Yong-jiao, ZHAO Li-juan E-mail: yjsong20170064@sicnu.edu.cn；lijuan_zhao@sicnu.edu.cn

Cite this article:

WANG Ning,XIAO Lin,BAI Yu-long, et al. Research on the Aging Structure of Silicone for Unearthed Ivory Storage[J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2025, 45(06): 1592-1597.

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2025)06-1592-06 OR https://www.gpxygpfx.com/EN/Y2025/V45/I06/1592

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