The Study Of Spinning Formation Of Cellulose Fibers With1-Butyl-3-methylimidazolium Chloride As Solvent

The regenerated cellulose fibers which have been commercialized were prepared by the traditional Viscose and N-methylmorpholine-N-oxide (NMMO) technologies. The traditional Viscose technology to produce regenerated cellulose materials has caused serious environmental burdens. However, the regenerated cellulose fibers made by NMMO not only show good mechanical properties, but also less pollution during the manufacturing. The method with ionic liquid as the solvent would be an environment-friendly way to fabricate regenerated cellulose fibers. In this paper, the dissolution of cellulose, formation thermodynamics and dynamics of [BMIMJC1, spinning technologies and post treatment methods of regenerated cellulose fibers with l-N-Butyl-3-methylimidazolium chloride ([BMIMJC1) as the solvent were investigated to guide the design of the formation engineering and optimizing of technologies.Firstly, the morphology and crystalline structure developments of cellulose during the dissolution in [BMIM]C1were investigated by optical microscope, synchrotron radiation wide-angle X-ray diffraction (WAXD) and FT-IR spectroscopy. Neither swelling nor dissolution of cellulose was observed under the melting point of [BMIM]C1(68℃). When the temperature was elevated to70℃, the swelling phenomenon of cellulose was exhibited with the interplanar spacing of (110) and (020) planes increasing slightly. With the temperature further going up to80℃, cellulose was dissolved completely. These phenomena indicated that the crystalline structure of cellulose didn’t destroyed and transferred in its swelling, but in it’s dissolution the crystalline structure of cellulose was destroyed completely and transformed into amorphous structure. The crystalline structure of the regenerated cellulose transformed to the II-type from the I-type.The linearized cloudpoint curve correlation (LCP) function used to build the binodal curve of whole concentration area for Cellulose/[BMIM]Cl/H2O. The experiment results shown that H2O can be used as coagulant for cellulose/[BMIM]Cl system. The interaction parameters of H2O/[BMIM]Cl and Cellulose/[BMIM]Cl were determined based on the mixed Gibbs free energy and viscometry methods, respectively. According to the Flory-Huggins theory, the Cellulose/[BMIM]Cl/H2O ternary phase diagram of whole concentration area was calculated by the subsequent iteration. Comparing Cellulose/[BMIM]Cl/H20ternary phase diagram and Cellulose/NMMO/H2O ternary phase diagram, it is found that Cellulose/[BMIM]Cl/H2O ternary phase diagram shown the smaller homogeneous phase regions and the larger metastable phase regions.The diffusion dynamics of [BMIM]Cl during coagulation of cellulose filaments with H2O as the non-solvent were investigated in detail. The diffusion coefficients of [BMIM]Cl was calculated based on the Fick’s second law of diffusion according to the experimental data. Several factors which affect the coagulation process including polymer concentration, concentration and temperature of coagulation bath were discussed, respectively. It was found that the diffusion rate of [BMIM]Cl decreased with increasing polymer content in the spinning solutions and the initial concentration of [BMIM]Cl in the coagulation bath, while the diffusion coefficients increased obviously with the coagulation temperature becoming higher. Compared with the diffusion process of NMMO from cellulose filament, the diffusion coefficients of [BMIM]Cl was lower, which suggested a stronger coagulation and washing conditions should be taken to produce regenerated cellulose fiber with [BMIM]Cl as solvent.Further, the synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) were carried out to analyze the supermolecular structure and the micro-morphology of regenerated cellulose fibers with [BMIM]Cl as solvent. The effect of stress on the spinning line, draw ratios, coagulation length, wetting and drying treatment, different spinning processes, stretching and different technology processes on the crystal, orientation and micro-morphology structure of regenerated cellulose fibers were discussed completely.The results of stress on the spinning-line, draw ratio and coagulation length shown that the crystallinity, crystal orientation, the length and orientation degree of microvoids, breaking strength and E-modulus of regenerated cellulose fibers increased with increasing stress on the spinning line, draw ratio and coagulation length increased, but the elongation at breaking reduced.For the post treatment of regenerated cellulose fiber, the microvoids along the fiber axis became shorter and the strength as well as initial modulus decreased when the cellulose fibers were wetted by water, but the radius of microvoids in cross-section increased slightly. After drying, the crystal orientation, strength and initial modulus of the regenerated cellulose fibers increased while the elongation at break decreased. It can be concluded that both the microvoids and crystal orientation decrease during wetting and drying treatment, which were the key factors influencing the mechanical properties of the treated cellulose fibers.Online stretching results showed that radius of microvoids in cross-section decreased with increasing of draw ratios, generally. But the microvoids length and orientation degree of cellulose fibers along the fiber direction increased.The studies of technology processes results indicated that the crystal orientation, crystallite size and crystallinity of Lyocell and IL-cell fibers from the dry-jet-wet-spinning technology were higher than those of Viscose and Newdal fibers from the wet-spinning technology. The technology process had little effect on the radius of the microvoids. The microvoids in Viscose and Newdal fibers have longer length (L) and greater misorientation (Bφ) than that in Lyocell and IL-cell fibers. This revealed that the average microvoid volumes of Viscose and Newdal fibers were larger. Furthermore, the regenerated cellulose fibers from dry-jet-wet-spinning process exhibited completely higher E-modulus, tenacity than that of the fibers spun by wet-spinning method did. By comparison, the ionic liquids can be a new direct solvent to prepare the regenerated cellulose fibers with less pollution. Finally, the cellulose/silk fibroin composited fibers were prepared from the dry-jet-wet-spinning technology with [BMIM]Cl as solvent and water as coagulant. The experiment results indicated that water can be used as nonsolvent to coagulate the cellulose/silk fibroin/[BMIM]Cl solution. There was interaction between the mac-romolecules of cellulose and silk fibroin in the solution. With increasing cellulose contents in the composited fibers, interaction between the macromolecules, the thermal stability, mechanical properties and spinnability of composited fibers increased. The morphology structure of fibers was more uniform, and the defect of hard and crisp of regenerated silk fibroin were improved obviously.