丝素湿法纺丝中凝固浴对再生丝结构影响机制.

As a natural protein fiber with good biocompatibility, silk has a lot of wastes in production, processing, weaving and after-use. Based on the principle of sustainable development, silk fibroin protein can be recycled by chemical method. After recycling, silk fibroin solution can be obtained and recycled silk fibroin materials can beprepared for reuse. Wet spinning is the first to be developed and applied in industrial production because of its uniqueness. As the process has been optimized in industrial production for a long time, wet spinning has become a relatively mature spinning method in all aspects. The choice of coagulating bath plays a key role in the solidification of spinning fluid in the coagulating basin, especially in the mechanical properties of RSF fibers. Sodium dodecyl sulfate (SDS) is a typical anionic surfactant with good emulsification performance, low skin irritation, high safety, and can interact with protein. Based on this, the study intends to establish a wet spinning process using SDS as the solidifying agent. In the paper, SDS was used as the coagulation bath to improve the ductility of regenerated silk fibroin fibers. First of all, the silk was degummed through degumming and other pretreatment, and then the degummed silk obtained after drying was dried for later use. After that, the degummed silk was dissolved with the formic acid-calcium chloride solution to obtain the spinning stock solution. In this way, deionized water, 75% ethanol solution and 50g/LSDS solution were selected as the coagulation bath for wet spinning, and three kinds of RSF fibers were obtained. In the end, the mechanical properties and aggregation structure of three RSF fibers were analyzed. Subsequently, the mechanism of SDS promoting fibrogenesis was verified by the fluorescence probe method. The morphology of the three kinds of RSF fibers was characterized by scanning electron microscope. Deionized water was used as the coagulation bath to obtain the most surface folds and the largest diameter of recycled silk. The recycled silk with ethanol as the coagulation bath has a roughly round cross section, smooth surface and the smallest diameter. When SDS is used as the coagulation bath, the cross section of fiber is approximately elliptic, with a few furrows on the surface and moderate thickness. Tensile tests were conducted to the three kinds of RSF fiber samples. The results show that when SDS is used as the coagulation bath, RSF shows the characteristics of elastic materials, and its fracture strain is 126%, which is much higher than that of the two kinds of regenerated fibers using deionized water (20%) and 75% ethanol solution (26%) as the coagulation bath. In order to explore the effect of the coagulation bath on the aggregation state of recycled silk, Fourier transform infrared spectroscopy (FTIR) was first used to analyze the secondary structure. The contents of three RSF secondary structures were obtained by the peak separation of amide Ⅰ region, and specifically, the recycled silk with SDS as the coagulation bath had the highest β-folding content. The content of β-folding of recycled silk in the coagulating bath with 75% ethanol was the lowest. In order to further explain the relationship between the mechanical properties and protein structure, X-ray diffraction was used to characterize the crystallization of the three kinds of RSF fibers, and it can be seen that the crystallinity degrees of the regenerated fibers are all low. In order to further explain the relationship between β-folding and the crystallization region, differential scanning calorimetry analysis was carried out for the three kinds of RSF, which confirmed the presence of β-folding in large quantities in RSF(SDS) fiber samples. The effect of SDS on silk fibroin protein was characterized by fluorescence probe. The results show that the surface of silk fibroin protein can produce more β-folds at the same time in the presence of SDS. In this study, SDS was used as the coagulating bath for wet spinning, anionic surfactant was innovatively introduced as the composition of coagulating bath, and a recycled silk material with high extensibility was obtained, providing a new research idea for silk fibroin protein wet spinning. In this paper, only the influence of the coagulation bath on the properties of recycled silk has been investigated, and the influence of post-treatment on the properties of recycled silk has not been involved. RSF(SDS) fibers, with excellent fracture elongation, can be treated to further improve the properties of recycled silk fibers. [ABSTRACT FROM AUTHOR]