Preparation And Characterization Of MWCNTs/Cellulose Fibers Using Ionic Liquids As Solvent

Ionic liquids as a kind of green solvents of cellulose have wide potential applications in the production of cellulose fibers. However, so far the researches on the cellulose/ionic liquid solutions are still at the preliminary stage and the obtained cellulose fibers only can be used in the dress field but have not fitted in with the requirements for industry and other fields. Currently, many studies have shown that the modification of the polymer system using carbon nanotubes as additives has become an effective way for the preparation of high-performance or functional polymer materials. Therefore, to modify cellulose fiber using this type of additives and to expand its applications in industry and other fields are gradually attracted much attention of researchers.To the date, the dispersity of carbon nanotubes in 1-butyl-3-methylimidazolium chloride ([BMIM] Cl) ionic liquid and its effect on the structure and properties of regenerated cellulose fiber have not been reported. Therefore, in this thesis, the [BMIM]C1 ionic liquid was used as a solvent of cellulose and the dispersion stability of multiwalled carbon nanotubes (MWCNTs) in [BMIM]C1 was investigated. And the properties of the resultant cellulose spinning dopes were also studied. Furthermore, the cellulose fibers modified with MWCNTs were prepared by the dry-jet wet spinning process and the structure and properties of the composite fibers were investigated.In this thesis, the purification, grinding and functionalization of MWCNTs as well as its dispersion stability in the [BMIM]C1 ionic liquid were firstly studied. The TEM、FTIR and Raman results showed that the purity of MWCNTs was increased and the carboxylic and hydroxyl groups existed on the surface of MWCNTs after being treated with the nitric acid. The results by sedimentation test, absorbance analysis and using microscope further showed that the purification with the nitric acid, the grinding and the functionalization with some suitable surfactants are some ways to improve the dispersity of MWCNTs in the [BMIM]C1 ionic liquid. In various ways, combining purification in nitric acid and then functionalization in sodium dodecylbenzene sulfonate (SDBS) aqueous solution with grinding is the most effective way. And the MWCNTs modified using this way could be dispersed uniformly in the [BMIM]C1 solution and the homogeneous MWCNTs/cellulose/[BMIM]Cl spinning dopes were obtained.The effect of MWCNTs on the rheological behaviour and spinnability of the cellulose/[BMIM]Cl solution was also studied by HAAKE rheometer and two type spinning devices. The results showed that the cellulose/[BMIM]Cl solution filled with MWCNTs belongs to the typical shear thinning fluid. Both the apparent viscosity and elasticity of the solution were increased firstly with the addition of MWCNTs and reached their highest values with adding 1% MWCNTs, then decreased with the further addition of MWCNTs. In the range of our experiments, it was found that the higher the content of MWCNTs in the cellulose/[BMIM]Cl spinning dope, the worse the spinnability was. The spinning process was run smoothly if the content of MWCNTs was less than 1%.Based on the above work, the structure and properties of MWCNTs/cellulose fibers were further investigated with tensile meter, SEM, WAXRD and two dimentional X-ray diffraction etc.. It was found that MWCNTs/cellulose fiber still had the cellulose II crystal structure. An appropriate amount of MWCNTs could be dispersed uniformly in the cellulose matrix and that could improve the mechanical properties of composite fiber. Compared with the fiber without MWCNTs, the tenacity and modulus of the composite fiber containing 1% MWCNTs were increased by 22.7% and 66.7%, respectively. And increasing the spinneret draw ratio appropriately can also improve the mechanical properties of MWCNTs/cellulose fibers. In addition, MWCNTs in the fiber almost aligned along the axis of the fiber and the orientation of MWCNTs increased with the increasing draw ratio. The results from TGA and electrical resistance analysis further showed that the addition of MWCNTs can improve the thermal stability of MWCNTs/cellulose fiber using ionic liquid as solvent. Moreover, it was found that more MWCNTs content and lower draw ratio could improve the electrical conductivity of the composite fiber.