Influences Of Solvent And Coagulation Bath On The Properties Of Regenerated Silk In Wet Spinning Of Silk Fibroin

Mulberry silk and its regenerated fibers are paid more attentions from researchers due to its biocompatibility and mechanical properties.The wet spinning technology can be used to prepare the regenerated silk,which allows for the recycling of silk offcuts and the waste silk fibers.In the present work,the dissolution behaviors of mulberry silk in inorganic salt/water system and formic acid/calcium chloride system were explored,respectively.The effects of coagulant type,solvent incubation and drafting post-treatment on the mechanical properties of the regenerated silk fibers were also examined.The obtained results of this study are listed as follows.Firstly,the effects of two inorganic salt dissolution systems,including Ca Cl₂/C₂H₅OH/H₂O and Li Br/H₂O on the molecular weight and rheology of the silk proteins were investigated,and a highly concentrated silk protein solution was prepared.Regenerated silk protein fibers were prepared by wet spinning,and the cross ponding mechanical properties were evaluated.Moreover,scanning electron microscopy,polarized light microscopy,X-ray diffraction and other technical means were used to analyze the structure and composition of the regenerated silk fibers.The results show that it is easier to prepare a solution with high molecular weight and spinnability by using the Li Br/H₂O as the solubilization system of silk protein.The high concentration of silk protein solution with highβ-folding ratio and less gelation can be obtained by using the proportioning method.The resulting regenerated silk impregnated with glycerin can improve the elasticity of regenerated silk fibers to a certain extent.Moreover,the influences of different volumes of FA/Ca Cl₂ solution and solubilization time on the rheology of regenerated silk protein solutions were also explored.The effects of p H and coagulant type on the performance of regenerated silk were compared,and the mechanism of fiber forming promoted by the coagulant of sodium dodecyl sulfate was explored.The regenerated silk fibers were subjected to solvent impregnation and draft post-treatment,and the structure was analyzed using scanning electron microscopy,mechanical and thermal property testing,infrared spectroscopy and X-ray diffraction.The results show that 200 g/L of formic acid/silk proteins solution suitable for spinning can be obtained by dissolving at 20°C for 4 h.50 g/L SDS at p H 4 was chosen as the wet spinning coagulation bath.The regenerated silk fires with a high tensile strength of 95.5 MPa and an elongation at break of 35.76%can be obtained after the combined use of glycerin impregnation,double drafting and ethanol impregnation.SDS can promote the fibroin fabrication by inducing the rapid formation of a large number ofβ-folds,and the regenerated fibroin fibers exhibit the characteristics of flexible materials.In summary,the silk fibroin solution dissolved by Li Br/H₂O was concentrated by the proportional optimization method,and the high concentration of silk fibroin protein solution was obtained.SDS as a wet spinning coagulant can induce the conformational transformation of silk fibroins,which is beneficial to the forming and processing of the regenerated silk fibers.The present work has the significance to reveal the dissolution mechanism of silk fibroin protein and the construction of regenerated silk fibers.