Silk artifacts constitute a vast heritage of mankind, but they are affected by degradation that alters the secondary structure of fibroin and weakens the mechanical properties of the objects, threatening their preservation. Current restoration practice still lacks feasible and compatible consolidants for historical silk.<br/>We propose a sustainable and inexpensive “green” method based on the use of renewable silk scraps to restore fragile silk fibers. Self-regenerated silk fibroin (SRSF) films with controlled crystalline-amorphous content were obtained from waste silk, by varying the concentration of colloidal fibroin dispersions, as demonstrated by 2D micro-Fourier transform infrared spectroscopy Imaging and spectral deconvolution.<br/>The tunability of this treatment allows easily control of the mechanical properties of degraded silk fibers. Highly amorphous SRSF films, cast from low-concentration dispersions, recovered the ductility of aged, fragile silk, likely due to the presence of domains with high fibroin chain mobility adhered to the silk fibers. Accordingly, highly crystalline (and thus brittle) films reduced the tensile strength and elongation length of the treated fibers.<br/>The whole cycle, starting from waste silk scraps to end with the consolidation of aged silk, makes a representative example of how chemistry can improve resiliency of cultural heritage through a circular-economy type of process, opening new perspectives for the preservation of historical textile collections and for the formulation of biomaterials or composites with enhanced properties.

Colloidal fibroin dispersions for the reinforcement of aged silk

ACS Fall 2021

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