Study Of The Self-stratification Unfolding Technology Applied On The Fragile And Bonding Unearthed Silk Relics

The unearthed textile with its variety forms and exquisite crafts possess great historical, scientific and artistic value, is also a highlight in the history of Chinese civilization which reveals the intelligence of ancient people. However, suffering from the long time burial, most of the textiles degraded and disappeared, the remained few seriously decayed and are extremely fragile. Serious degradation and interlayer adhesion are the general characters of unearthed textiles. Therefore, unfolding the adhesive textiles, especially for utilizing the available techniques to improve the current status of degraded and adhesive unearthed textiles is the first and key step of conducting conservation and restoration works.Currently, physical, chemical and biological tools are employed in developing the unfolding agent and technology for silk textile relics, to reduce the force of interlayer adhesion. The chemical ingredients of unfolding agent are mainly the biochemical fertilizer of surfactant, softener and penetrant etc., which could effectively reduce the intensity of interlayer adhesion. Due to the low strength, even reducing the force of interlayer adhesion, the unearthed fragile textile would be damaged upon unfolding.Therefore, maintaining the strength which is sufficient for overcoming the intensity of interlayer adhesion is a pre-condition for textiles to qualify for unfolding.Generally speaking, reducing the force of interlayer adhesion is in conflict with increasing the mechanical strength of silk, which limited the development of unfolding techniques. If improving the strength of silk, intensity of interlayer adhesion would increase upon the infiltration of reinforcement agent, vice versa. In this paper, self-stratifying technology was used in unfolding the silk relics to reduce the intensity of interlayer adhesion as well as increase the mechanical strength of silk fiber.Polyvinyl acetate and sodium stearate were selected as the self-stratify material to predict the layering after filming based on surface energy theory. SEM was employed to verify the layering efforts and ensure the material to satisfy the pre-condition of self-stratify unfolding, and then it was tested on the simulated samples. The orthogonal experiment of concentration ratio and acting time were designed by characterizing the unfolding efforts with peel strength and tensile strength. 0.5% Polyvinyl acetate and 0.5% sodium stearate were selected as the optimal recipe with acting time of 4h.FIB was used to implement a stereoscopic analysis by obtaining the different depth of gradient space data for unfolding agent film. AFM and XPS were used to analyze the processed samples. Stratification presented longitudinally on the film was observed under SEM. By comparing the upside and downside surface as well as the different depth, it was found that the main ingredient of the film is sodium stearate, it reduced upon the increase of the depth, and polyvinyl acetate increased accordingly. XPS results showed the relative content of Na for upside surface, middle and downside surface were respectively 5.05%、3、03%、0.37%、0.42% which indicated a trend. Raman was used to measure the content of polyvinyl acetate at different position of the film, the results were 18.7%、22%、61.7%、69.2% which showing a graded change. These results proved the stratification of self-stratifying unfolding reagent.3D microscope was used to observe the changes of the simulated samples and silk samples collected from Xiejiaqiao Han tomb, Xiajiatai Chu tomb and Nanling Tieguai Song tomb after unfolding, no obvious change was found. A thin layer was found on the surface of silk through SEM by comparing the morphology before and after unfolding. The results of chromatic difference analysis of simulated samples,Xiejiaqiao samples,Nanling samples and Xiejiatai samples were 0.82、0.56、0.96、0.70, which conform to the required color change range of heritage conservation. The hardness test found the huge decrease in the hardness and anti-bending of simulated and ancient samples after unfolding, which indicated some of the contaminants were washed away from the surface of the silk. The use of the unfolding reagent also increases the softness of the silk. The TGA results indicated the changes in the thermo stabilization of silk as well as the thermal decomposition rate. The results of DTMA indicated the increase of the tensile strength after unfolding the silk.Isothermal titration thermal technology, TGA and parallax scanning thermal analysis were employed to characterize the reproducibility of self-stratify technique,the results proved its good reproducibility which meet the requirements of heritage conservation. The stratifying efforts, unfolding results and unfolding reagent removing efforts were evaluated on simulated and ancient samples. The self-stratify technique were tested on samples of Xiejiaqiao Han tomb, Nanling Tieguai Song tomb and Haihunhou Han tomb, all obtained with good results.The self-stratifying unfolding technique of silk changed the traditional approach for only reducing the intensity of layer adhesion, instead, formed a new research angle of increasing the mechanical strength and reducing the layer adhesive strength of silk at the same time. It provided with a new method for unfolding silk relics, as well as offering guidelines for other heritage conservation works.