Process And Mechanism Of Wet Spinning Regenerated Silk Fibroin

Natural fiber has been favored by consumers for its unique merits, especially the natural silk fibroin has a great application potential in biological tissue engineering, membrane filtration material and medical fields besides the reputation of "fiber queen" in dressing aspect, because of its good bio-compatibility and is non-toxic, pollution free and non-irritan. In this paper, the wet spinning process of tussah silk fibroin fiber regeneration was discussed and the waste silk fibroin fiber regeneration guidance was given.The subject takes tussah silk fibroin powder as raw material, using step solution method, then the nanometer protein was dissolved in the three yuan solvent of LiSCN, C2H5OH and H2O to form spinning solution. In reference to acrylic wet spinning process, the spinning process of coagulation bath, predrawing bath, washing bath,drawing bath and drying densification was adopted to realized the silk fibroin fiber regeneration considering the particularity of silk fiber structure. In this thesis, the influence of process parameters on fiber morphology and structure was discussed, the evolution of the structure in the forming process was researched.The research showed:The concentration of coagulation bath affect primary fiber mainly through the effect of thread surface solidification, and the coagulation bath temperature affect the dope thread mainly on the core department of solidification. The draw ration of primary fiber in pretensionning bath increases in the first, the decreases along with the coagulation bath concentration and temperature.. When the setting rate is slower, the fiber structure was dense and form round section easily; Conversely, the fiber solidification was violent, the structure defect is more, cross section will be oval. It is known that, when the concentration of (NH4)2SO4is400g/L, the temperature is15℃, fiber can realize good forming through the single factor experiments. The purpose of adding LiSCN and L(NH4)2SO4predrawing bath is to affect the concentration difference and adjust its further forming speed, research shows that6%LiSCN,380g/L(NH4)2SO4can harmonic fiber solidification and prestretching contradiction. The appropriate water temperature is55℃～60℃in drawing bath.The drawing and drying densification play an important role in the fiber forming process, affecting the structure and properties. Research shows that, with the draw ratio increases, the crystallinity and orientation degree are increased and the mechanical performance and thermal stability performance have been improved. The drying densification process favors the crystal growth and perfect while consolidating the orientation texture, and the temperature and the time are both important. Too short time can not reach the densification effect, but too long time is a big waste of energy; The capillary suction can not easily formed when the temperature is low, and moisture volatilizes limitation; but too high temperature will make the fiber yellow and crisp in a short time. Experimental results shouw that:the fiber can achieve ideal effect in the135℃environment leaving15min.The evolution of the fiber structure in the forming process was also discussed in this topic. Through the SEM, infrared spectrum, the X-ray diffraction and the polarized-light microscope analysis, we can found that the structure of the fiber become more and more dense and it is a gradual process. Fiber achieve homogenizing basically after the drying densification process.