| Cellulose (CE) and silk fibroin (SF) are two natural biorenewable polymers that are widely used in the textile industry. In spite of numerous studies on the dissolution and preparation of regenerated SF, lack of a good solvent system has always been the major challenge. Recently, it was discovered that1-Butyl-3-Methylimidazolium Chloride ([BMIM]Cl) could be utilized as a single step solvent for the preparation of a stable CE/SF solution as well as a spinnable homogeneous dope solution. Therefore, the dissolution of cellulose and silk fibroin and the subsequent preparation of blend films and fibers were studied.Firstly, the dissolution kinetics of cellulose and silk fibroin in [BMIM]Cl was investigated by optical microscope. Neither swelling nor dissolution of cellulose or silk fibroin was observed under the melting point of [BMIM]Cl (68℃). However, when the temperature was elevated to80℃, there was evidence of the swelling phenomenon of silk fibroin and of cellulose at85℃. With the temperature further going up to90℃, both materials dissolved completely within4hours.Secondly, in order to investigate whether the CE/SF blend is spinnable, the rheological properties of the blend solution were analyzed by blending cellulose with silk fibroin in ionic liquid to produce mixtures having weight ratios of90/10,80/20,70/30,60/40,50/50,40/60,30/70and20/80. The viscosity and dynamic modulus of SF dope exhibited Newtonian behavior, but as the cellulose concentration increased, the effect of shear thinning became visible as an indication that a higher concentration of cellulose in the dope would result in good spinnability. From the dependence of zero-shear viscosity on temperature, it is shown that the flow activation energy(Eη) of cellulose/silk fibroin/[BMIM]CI spinning dopes with different intrinsic viscosity was different depending on the ratio of cellulose, showing that the solution is sensitive to temperature. It was established from the mixture rule that the solution with cellulose to silk fibroin ratio of8:2had a positive deviation signifying the most stable and homogeneous solution. Also, a different approach was employed to prepare CE/SF blend solutions; where CE/[BMIM]Cl solution is mixed with separately prepared SF/BMIMCl solution for1hour. Kinetics of gel formation and shear induced changes in viscosity were tracked using rheology. The method of solution preparation had no effect on the gelation temperature, shear and complex viscosity or on visco-elasticity of blend.Thirdly, blend films were prepared from CE/SF/[BMIM]Cl solution by changing dope formulation and coagulant. Their thermal stability, morphology and structure were measured to investigate the effects of various coagulants and weight content of SF (wSF) on the structure and properties of the blend membranes. Results revealed that ethanol is the suitable coagulant which induces stable P-sheets and cellulose â…¡ resulting in insignificant protein component extrusion. Films coagulated in water had almost no protein, indicating that silk fibroin existed in a water soluble form. Upon dissolution, the crystalline structures were destroyed completely and transformed into amorphous structures. At regeneration, this crystalline structure transformed to the â…¡-type from the â… -type for cellulose and to β-sheets for silk fibroin.Finally, various compositions of cellulose/silk fibroin composite fibers were prepared from dry-jet-wet-spinning technology with [BMIM]CI as solvent and ethanol as coagulant. Regenerated CE/SF fibers were collected at different draw ratios and air gaps and their physical and mechanical properties were characterized. The tensile property was strongly dependent on the draw ratio and the morphology structure of fibers was more uniform. A breaking strength of2.38 cN/dtex and elongation to break of almost7%were obtained with a5-mm air gap for the blend containing8%(w/w) CE/SF8:2.This thesis presents a detailed study of cellulose/silk composite fibers with commendable characteristics of cellulose and silk... |
