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The dissolution of cellulose in different ionic liquids will be described as a very recent subject for a direct dissolving process, which was used to prepare regenerated cellulose fibres. The preparation of the dopes was arranged starting from slurry of cellulose in the aqueous ionic liquid by removing the water at elevated temperature, vacuum and high shearing rates. As ionic liquids, the 1-N-Butyl-3-methylimidazolium...
Cellulose (7% water) was thoroughly dispersed in various ionic liquids (IL) and the turbidity of the mixture was investigated to distinguish real dissolution from fine dispersion. The dissolving ability of 1-butyl-3-methylimidazolium chloride (BMIMCl know cellulose solvent) and 11 other commercial IL (not reported as cellulose solvents) was studied. From the latter, only 1,3-dimethylimidazolium dimethylphosphate...
To better understand the complex interactions leading to dissolution of cellulose in ethylene diamine (EDA)/salt solvents, studies of interactions in sub systems of solution components and a model system based on cellobiose were conducted. Interaction between EDA and salt cation was investigated through comparison of solvation of K+, Na+ and Li+ in the EDA/H2O binary solvent system. The least degree...
Properties of cellulose solutions in different direct dissolving liquids such as N-methylmorpholine-N-oxide and ionic liquids with varied cations and anions were investigated. The effects of different cations and anions of the used ionic liquids on the solution state were studied on the basis of the rheological characteristics of the resulting polymer solutions. The influence of these components is...
The ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([emim][OAc]) readily dissolves high concentrations of cellulose. However, the high viscosity of [emim][OAc] (162 cP at 20 °C) could limit its use as a solvent for cellulose. Dissolved CO2 has been shown to decrease the viscosity of ILs. In this study, a 50 psi CO2 environment was applied for the dissolution of cellulose in [emim][OAc] to determine...
A systematic study of variables that affect the fiber welding process is presented. Cotton cloth samples are treated with controlled amounts of 1-ethyl-3-methylimidazolium acetate for a series of times and temperatures. Diluting the ionic liquid with a volatile molecular co-solvent allows temporal and spatial control of the welding process not possible with neat ionic liquids. Materials are characterized...
N,N-Dimethylacetamide/lithium chloride (DMAc/LiCl) mixture is a popular solvent system used for cellulose dissolution, analysis, and derivatization. However, a pre-treatment (activation) procedure is needed for most celluloses to dissolve readily in DMAc/LiCl. Here, an optimized version of the activation protocol based on solvent exchange to 1,4-dioxane was introduced. Its universality was demonstrated...
It was considered that the dissolution of cellulose in alkali solutions is mainly due to the breakage of hydrogen bonds. As an alkali hydroxide, KOH can provide OH− just like LiOH and NaOH; but it is well known that LiOH and NaOH can dissolve cellulose, whereas KOH can only swell cellulose. The inability of KOH to dissolve cellulose was investigated and the mechanism of cellulose dissolving in alkali...
The swelling and dissolution phenomena of microcrystalline cellulose (MCC) were investigated in subcritical and supercritical water. Commercial MCC was treated in water at temperatures of 250–380 °C and a pressure of 250 bar for 0.25–0.75 s. As reaction products, undissolved but depolymerised cellulose residue, short-chain cellulose precipitate, water-soluble cello-oligosaccharides and monosaccharides,...
N-methylmorpholine N-oxide (NMMO) is a known cellulose solvent used in industrial scale (LyoCel process). We have studied interactions between pretreated softwood pulp fibers and aqueous NMMO using nuclear magnetic resonance (NMR) spectroscopic methods, including solid state cross polarisation magic angle spinning (CP-MAS) 13C and 15N spectroscopies, and 1H high resolution MAS NMR spectroscopy...
Urea can improve the solubility and stability of cellulose in aqueous alkali solution, while its role has not come to a conclusion. To reveal the role of urea in solution, NMR was introduced to investigate the interaction between urea and the other components in solution. Results from chemical shifts and longitudinal relaxation times show that: (1) urea has no strong direct interaction with cellulose...
Dissolving grade pulps are used as raw material for manufacture of regenerated cellulose fibres and their use is constantly growing. Despite intensive research, there is still a need to develop cellulose dissolution-regeneration processes that would be economically viable, fulfil the pre-conditions of sustainability and would be able to meet the strict product quality requirements. The basis for creation...
The dissolution of different cellulose pulps from different sources such as wood, bamboo and ramie pulp in 7 wt% NaOH/12 wt% urea aqueous solution was investigated in the present article, as well as the structure and properties of the resultant regenerated films. All of the cellulose samples with molecular weight below 1.2 × 105 could be quickly and completely dissolved in NaOH/urea aqueous solution...
Subcritical and supercritical water are known to dissolve crystalline cellulose, offering a simple way to produce low molar mass cellulose which precipitates at ambient temperatures. However, the yield of precipitate is limited by concomitant degradation reactions. In this study, the formation of cellulose precipitate from six different microcrystalline celluloses (MCC) was investigated in 0.2 s treatments...
The rapid coagulation of NaOH-based cellulose solution during the wet spinning process leads to a low stretching ratio and, consequently, the low mechanical properties of the fibres. The aim of this work was to slow down the coagulation by replacing the sulphuric acid spin bath with an acetic acid bath. The spin dope was prepared by dissolving the enzyme-treated dissolving pulp in aqueous sodium zincate...
As a result of the constantly growing demand for textile fibres interest in utilising cellulose pulps for manufacturing regenerated cellulose fibres is growing. One promising water-based process for the manufacture of regenerated cellulosic products is the Biocelsol process based on an NaOH/ZnO solvent system. The drawback of the Biocelsol process is the need for pre-treatment of the pulp, i.e. long...
Dissolving pulps are used to manufacture various cellulose derived products through cellulose dissolution. Solubility of cellulose pulp has been claimed to be strongly dependent on the porosity development, the degree of polymerisation and the pulp viscosity. The removal of external cell walls has been proposed to have a key role in the pulp solubility. In this paper, the effect of the outermost surface...
Chitosan is a widely used biopolymer with very attractive properties. However, to compensate for the deficiencies in the application of this bio-macromolecule, many studies have been performed on the preparation of chitosan blends with various polymers, such as cellulose, which is abundant and unique with a tough bio-structure. Because of the different dissolution conditions of chitosan and cellulose,...
The amphiphilicity of solvent systems is realized for adjusting the dissolution of natural cellulose by making use of tetra-butylammonium hydroxide (TBAH) as an example. TBAH aqueous solution is found to have an obvious effect on adjusting its amphiphilicity, along with a flexible concentration ranging from 40 to 60 wt% for dissolving cellulose. With a suitable amphiphilic property, cellulose can...
In this study, ionic liquid treatment for increasing the wet strength of cellulose paper was studied. The effects of treatment conditions with the ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) on the wet strength were investigated. First, the [BMIM]Cl (20 g) was melted at 80–100 °C and the paper was immersed in it for 5–60 s. Next, the paper was immersed in ethanol, and finally, it...
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