明代丝织物保存状态的分析研究

Investigation on the preserved state of a silk fabric of Ming Dynasty

考古出土丝绸保存状态的研究对丝绸的科学保护具有重要的指导意义。本工作选取丝纤维中最主要的桑蚕丝及柞蚕丝作参照,以考古出土的明代丝绸为研究对象,通过荧光电子显微镜观察丝绸的纤维结构形貌、傅立叶变换红外光谱仪分析化学结构,结合X-射线衍射仪分析结晶度,用薄层色谱分析丝绸中氨基酸的组成,并进一步用紫外-可见光分光光度法分析丝绸中酪氨酸含量等方法,对一件出土的明代丝绸织物的保存状态进行了科学分析研究。分析结果表明,明代丝绸为桑蚕丝,纤维丝松散且断裂较多,结晶度下降,多数氨基酸含量明显降低,只检测到甘氨酸、丙氨酸、丝氨酸、酪氨酸与谷氨酸。酪氨酸含量为13.78%,比参照桑蚕丝含量低。

The investigation of the preserved state of ancient silk fabrics can provide important information for the archaeological study and scientific conservation. Therefore, it is indispensable to develop an accurate and reliable method to measure silk fabrics in order to obtain information on their original materials, aging situation and preserved state. Unfortunately, there are difficulties and limits in analyzing the silk fabrics because of their complex organic composition and the small quantity of sample available. Silk fabrics are easy to age when exposuring to acid or alkali environment and light. After aging, there are changes in the amount of amino acid, crystal degree of thread and structure morphology. The amount of tyramine is much richer among the eighteen amino acids in silk fabrics, and this can be an indicator for measuring the variation of tyramine before and after aging. In this study, samples from an excavated silk fabric of Ming dynasty were analyzed, and mulberry raw silk and tussah silk were selected as contrast samples. Fluorescence electron microscopy （FEM） , Fourier transform infrared spectrometry （b-TIR）, as well as X -ray diffraction（XRD） analytical techniques were used to characterize the matted morphology and crystal degree of the silk fiber. Both thin - layer chromatogram （TLC） and ultraviolet - visible spectrophotometer （ UV - Vis） were used to identify the typical amino acids and to measure the amount of tyramine. The analytical results indicated that the silk sample of Ming dynasty was a kind of mulberry raw silk, and the silk fiber was loose and broken with a decrease in crystal degree. The amino acids mainly consisted of glycin, alanine, serine and tyramine and their content was obviously reduced. The amount of tyramine in analyzed sample was 13.78% approximately, about 0.37 % lower compared with the mulberry raw silk sample. This paper described the preserved state of the silk fabric in qualitative and quantitative aspects. The combination of FEM, FTIR, X - RD, TLC and UV - Vis provided a reliable method for the analyses of silk fabrics.