Study On The Rheological Properties Of The RSF Solvent System And The Influence During Fiber Forming

With the enhancing awareness of the green environment protection consciousness ofpeople, and the excellent characters of the regenerated protein fiber, such as the goodbiocompatibility, healthy, care-skin, and so on. The development and the degree ofattention of the regenerated silk fibroin (RSF) fiber gradually increased in recent years.With waste silk fibers as the raw material, the right amount of glycerol as the plasticizer,the regenerated silk fibroin (RSF) solution with different content of plasticizer was made,and the rheological property, the spin-ability, the structure evolution during the fiberforming was researched in this thesis. The rheological property of the solution wasstudied, the results shown that: the RSF solution is non-Newtonian liquid and viscoelasticfluid with both elastic and viscid, and also with obviously shear-thinning features. Theaddition of the plasticizer made the viscosity of spinning dope steadily under the lowertemperature and shears rate condition, and with lower structural viscosity index andviscoelastic transition point, the rheology and spin-ability improved, the effect ofextrusion swelling weakened. The spin-ability of the solution was studied, the resultsshown that: the RSF solution with the plasticizer has better stability, with quite differentprocess design such as the air-layer height and the distribution of draw ratio, the spinneretand total draft during the fore-spinning was increased, which compared with the pureRSF solution. The change of the diameter, feature, orientation during the fiber formingprocess of the RSF solution with the plasticizer was studied, the results shown that: thefibers made by the spinning solution with the plasticizer, which with the higher stretchratio, the small and uniform diameter, and the relatively smooth and uniform vertical surface, the higher birefringence. The results of the infrared absorption spectrum and theX-ray diffraction analysis show that: during the RSF fibers forming process, themolecular conformation had been unchanged substantially which was still α-helix andrandom coil structure-based, the coexistence of a small amount of β-sheet structure, thecrystal structure which was still a large amount of unstably SilkⅠstructure, however,the addition of the plasticizer made the conformation to the β-fold structure, andfavorable for the formation of the SilkⅡstructure. It comes to the conclusion that: whenthe content of the plasticizer was9percent, in low temperature range between50and60℃and low shears rate range more than5s-1, the RSF solution with lower apparentviscosity and structural viscosity index, better liquidity, spin-ability and stability. Duringthe forming process, higher total draft multiple as6.5times was forced on the as-spunfiber, and finally got the fibers with uniform diameter and better degree of crystalline andorientation.