Resisting Pulverization of Silk Cultural Relics through 3D Structural Shaping and Mechanical Reinforcement

Developing advanced technologies for the consolidation and shaping of rotten/pulverized silk fabrics (RPSFs) is of vital historical and cultural value, but currently reported strategies are still far from satisfactory. In this regard, a poly(ethylenimine)/poly(ethylene glycol) diglycidyl ether/isopropyl palmitate (PEI/PEGDE/IPP) method was proposed in this work. Briefly, a spatially adaptive three-dimensional (3D) cross-linked PEI/PEGDE framework was constructed around the silk fiber bundles of an RPSF to enhance its structural integrity, strength, toughness, and elasticity through successive soaking of the RPSF in an ethanol solution of branched PEI molecules and an acetone solution of PEGDE molecules. Then, IPP molecules were introduced into the PEI/PEGDE framework through soaking the PEI/PEGDE-treated RPSF in an ethanol solution of IPP molecules (1 wt %) to improve the softness and ductility of RPSF. Through three systematic orthogonal experiments (i.e., stiffness, chromaticity variation, and mechanical properties), the optimal initial feeding composition of PEI and PEGDE was screened and determined to be 2 and 2 wt %, respectively. A series of compositions and structural identifications indicated that the consolidation/shaping mechanism of the PEI/PEGDE/IPP method fitted with our initial theoretical assumption. Besides, the PEI/PEGDE/IPP treatment increased the ordered arrangement of the interchain domain and the fiber axis of RPSFs and, therefore, could enhance the antitearing capability of RPSF, which posed a positive influence on the long-term preservation of RPSFs. When being applied to true RPSF historical relics (Han Dynasty), the PEI/PEGDE/IPP treatment did not change their morphology, geometry, color, and texture but could improve the mechanical stability of RPSFs to some extent. Thus, the reported PEI/PEGDE/IPP method is promising for the preservation of RPSF historical relics in the future.