Self-dialysis Wet-spinning Of RSF Fibers Containing Xanthate And Their Structure And Properties

In this paper, we studied the process of regenerated silk fibroin (RSF) using self-dialysis method. Bromide-lithium and ethanol mixed solution were used as a solvent of degummed SF, the RSF solution containing xanthate was obtained by adding sodium ethyl xanthate, and the RSF solution was wet-spun to form fibers. The properties of RSF solution and the structure and properties of the RSF fibers were studied. The result showed that the spinnability of the RSF solution was improved distinctly, at the same time the physical properties of RSF material was also meliorate, which gave theoretical and experimental support to the application of RSF materials. The experiment was divided into three parts:Firstly, the preparation and properties of RSF solution was discussed. The results showed that the RSF solution was shear thinning fluid which showed complicated rheology behavior. Properties of RSF containing xanthate was superior to that without xanthate , compared with the RSF solution without xanthate the spinnability of regenerated SF solution containing xanthate was improved markedly. The rheology behavior of RSF dope was affected by xanthate. The longest spinnable length (Lmax ) of RSF solutions containing xanthate was increased from 75cm to above 120cm, the structure viscosity index (Δη) was decreased and the non-Newton index (n) was increased. The spinnability of the RSF solution with the content of xanthate 5% ,7% and 9% were better, especially the dope with the content of xanthate 5% .Secondly,the spinning of RSF and the morphological characteristics of the filament was studied. The results indicated that the process condition of the RSF dope containing xanthate was improved. During the spinning process, the extruded fiber liquid didn't rupture but flowed fluently all the time. Compared with the RSF dope without xanthate the spinning temperature was decreased from about 45℃to 30℃. The result of SEM showed that the microfibrils structure of the surface of the RSF fibers containing xanthate was improved compared RSF fiber without xanthate, and the microfibrils of the fiber were obviously oriented along the fiber axis. The surface of RSF fiber spun into a MeOH coagulation with the content of xanthate 5% is the smoothest. In addition, the cross-section of the filament spun into a EtOH coagulation was smooth and showed no pore structure morphology, and the surface was smoother and showed no microfibrils pore structure. The surface of the RSF fibers with the content of xanthate 5% had less small flute, and especially that with the content of xanthate 7% and 9% become smoother while the surface was rugged when a MeOH is used as a coagulant.Thirdly, the structure and properties of RSF fiber were investigated through X-ray diffraction, FTIR, Raman spectrum, TGA, electron single-fiber tensile tester. The results showed that the RSF as-spun fibers had lower crystalinity compared with those without xanthate. The strenghth and elongation of RSF drawn fiber with xanthate spun into a EtOH coagulant was enhanced obviously. The strenghth and elongation of RSF drawn fiber with xanthate content 7% is 1.6cN/dex and 5.87%,while that of RSF drawn fiber with xanthate content 9% is 1.3cN/dex and 22.94%, respectively.