酸性水解条件下丝织品的结构及稳定同位素变化

Structure and stable isotope changes of silk fabrics under the condition of acidic hydrolysis

为了解丝织品文物在酸性条件下水解劣化对结构和稳定同位素比值的影响,通过现代样模拟丝织品在酸性溶液中水解老化的过程,对老化后丝织品的表面形貌及色差变化进行观察,并采用万能材料试验机、傅里叶变换红外光谱仪、X射线衍射仪和同位素质谱仪对老化前后丝织品的力学性能、二级结构及稳定同位素比值进行了比较。结果表明:丝织品的酸性水解老化速率在前7 d较快,丝织品表面结构破坏严重,力学性能下降明显,此后老化速率变缓慢;二级结构变化中,结晶区被破坏,β-折叠结构相对含量下降,α-螺旋结构和无规卷曲结构相对含量增加,结晶度不断下降;稳定同位素比值在酸老化前后变化较小,酸性水解对老化丝织品的δ;H、δ;O、δ;C和δ;N影响不明显。

In order to know the influence of hydrolytic degradation of silk fabric relics under acidic conditions on the structure and stable isotope ratio, modern silk fabric samples were used to simulate the process of hydrolytic aging in acid solution. The surface morphology and color difference changes of silk fabrics after aging were observed. The mechanical properties, secondary structure and stable isotopic ratio of silk fabrics before and after aging were compared using universal materials tester, Fourier transform infrared spectrometer, X-ray diffractometer and isotope mass spectrometer. The results indicate that the acid hydrolysis aging rate of silk fabrics is fast in the first 7 d. The surface structure of silk fabrics is seriously damaged, and the mechanical properties of silk fabrics are reduced significantly, followed by slackened aging rate. After analyzing the change of secondary structure of the samples, we find that the crystalline region is destroyed, the relative content of β-sheet structure decreases, and the relative content of α-helical structure and random coil structure increases. The crystallinity decreases continuously with the increasing aging time. The stable isotope ratio changes slightly before and after acid aging. Acid hydrolysis has no obvious influence on the δ;H, δ;O, δ;C and δ;N of aging silk fabrics.