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Cellulose, a natural, renewable, and environment friendly biopolymer, has been considered as a sustainable feedstock in the near future. However, only 0.3% of cellulose is today processed since it is not soluble in conventional solvents due to the strong hydrogen bonding network and highly ordered structure. Hence, the search of effective and eco-friendly solvents for cellulose dissolution has been a key pillar for decades. In the recent years, ionic liquids (ILs) have been proposed as green solvents for cellulose and have been applied for the production of cellulose-based fibers. This review aims to focus the attention toward fiber spinning methods of cellulose based on ILs, as well as recent progress in cellulose dissolution using ILs. Moreover, the development of cellulosic fibers blended with other biopolymers, and cellulose composites are presented. Finally, different applications of cellulose fibers and composites are summarized and discussed. [ABSTRACT FROM AUTHOR]

Cellulose is an historical polymer, for which its processing possibilities have been limited by the absence of a melting point and insolubility in all non-derivatizing molecular solvents. More recently, ionic liquids (ILs) have been used for cellulose dissolution and regeneration, for example, in the development of textile fiber spinning processes. In some cases, organic electrolyte solutions (OESs), that are binary mixtures of an ionic liquid and a polar aprotic co-solvent, can show even better technical dissolution capacities for cellulose than the pure ILs. Herein we use OESs consisting of two tetraalkylphosphonium acetate ILs and dimethyl sulfoxide or γ-valerolactone, as co-solvents. Cellulose can be first dissolved in these OESs at 120 °C and then regenerated, upon cooling, leading to micro and macro phase-separation. This phenomenon much resembles the upper-critical solution temperature (UCST) type thermodynamic transition. This observed UCST-like behavior of these systems allows for the controlled regeneration of cellulose into colloidal dispersions of spherical microscale particles (spherulites), with highly ordered shape and size. While this phenomenon has been reported for other IL and NMMO-based systems, the mechanisms and phase-behavior have not been well defined. The particles are obtained below the phase-separation temperature as a result of controlled multi-molecular association. The regeneration process is a consequence of multi-parameter interdependence, where the polymer characteristics, OES composition, temperature, cooling rate and time all play their roles. The influence of the experimental conditions, cellulose concentration and the effect of time on regeneration of cellulose in the form of preferential gel or particles is discussed. Regular micro-sized particles regenerated from a cellulose-OES mixture of tetrabutylphosphonium acetate:DMSO (70:30 w/w) upon cooling [ABSTRACT FROM AUTHOR]

Textile filaments were fabricated from a solution obtained from carboxymethylated cellulose dissolved in aqueous NaOH solution, by wet spinning in an acid coagulation bath. Spinning is possible for modified cellulose with a carboxyl group content of at least 1.3 mmol/g cellulose. A post-treatment—heating in the presence of sodium hypophosphite—improved the properties of these filaments. This is a novel process, much more environmentally friendly than the viscose process for the production of rayon, in which most of the chemicals can be reused making it likely that the process is economically viable. After extrusion in an acid bath, filaments containing 1.3 mmol –COOH/g cellulose could be washed with water quite readily, a process very difficult for filaments with carboxyl group content of 1.5–1.7 mmol/g cellulose. The tenacity of the filaments obtained from the modified cellulose with a carboxyl group content of 1.3 mmol/g cellulose was 1.0 cN/dtex, which was higher than that of the filaments with carboxyl group contents of 1.5 mmol/g cellulose (tenacity 0.93 cN/dtex) and 1.7 mmol/g cellulose (tenacity 0.88 cN/dtex). The water absorbency of the filaments made from the modified cellulose with carboxyl group content of 1.3 mmol/g cellulose was 0.54 g water/g filaments which was ~ 2 times and ~ 3.5 times lower than that of the filaments with carboxyl group contents of 1.5 mmol/g cellulose and 1.7 mmol/g cellulose, respectively. The values of tenacity and water absorbency for filaments with 1.3 mmol/g cellulose are extremely promising for textile applications. [ABSTRACT FROM AUTHOR]

Inappropriate discharge of industrial wastewater and household effluent has led to an accumulation of hazardous organic substances, oil and grease, heavy metal ions, dyes, and leftover pharmaceutical products in the aquatic environment. To mitigate the adverse effects of polluted water, various techniques have been implemented for physical, chemical, and biological wastewater treatments. In chemical wastewater treatments, utilizing polymers are among the most common pathways, in which cellulose-derived materials as one of the abundantly available lignocellulosic constituents have gained much interest for the applications. As environmental remediation agents, cellulose derivatives have great potential due to their biocompatibility, excellent mechanical properties, environmental friendliness, economic viability, low toxicity, and robustness. In a chemical wastewater treatment, cellulose derivatives can be valorized to various industrial applications, such as membrane technology, absorption and adsorption process, flocculant, a catalyst for chemical reaction, and disinfecting agent. In this review paper, various types of utilization methods of cellulose derivatives, ranging from nano, micro, and natural form in industrial wastewater and household effluent treatment, are extensively discussed. In addition, the cellulose performance in adsorption, filtration is also briefly elaborated and then compared with those of the conventional polymer-based materials, such as polyether sulfone (PES), Polyvinylidene fluoride (PVDF), and carbon nanofiber (CNF). [ABSTRACT FROM AUTHOR]

We report on a new process for the spinning of high-performance cellulosic fibers. For the first time, cellulose has been dissolved in the ionic liquid (IL) 1-ethyl-3-methylimidazolium octanoate ([C2C1im][Oc]) via a thin film evaporator in a continuous process. Compared to other ILs, [C2C1im][Oc] shows no signs of hydrolysis with water. For dope preparation the degree of polymerization of the pulp was adjusted by electron beam irradiation and determined by viscosimetry. In addition, the quality of the pulp was evaluated by means of alkali resistance. Endless filament fibers have been spun using dry-jet wet spinning and an extruder instead of a spinning pump, which significantly increases productivity. By this approach, more than 1000 m of continuous multifilament fibers have been spun. The novel approach allows for preparing cellulose fibers with high Young's modulus (33 GPa) and unprecedented high tensile strengths up to 45 cN/tex. The high performance of the obtained fibers provides a promising outlook for their application as replacement material for rayon-based tire cord fibers. [ABSTRACT FROM AUTHOR]

Abstract: Cellulose (Cell) microfibrils were prepared from regenerated Cell fibers with facilitated fibrillation character by immiscible polymer blending with polyacrylonitrile (PAN) as a minor component. The blend fibers were spun by dry-jet wet spinning of the liquid-liquid phase-separated Cell/PAN solution using the well-known ionic liquid 1-buthyl-3-methyl imidazolium chloride as a cosolvent. Wide angle X-ray diffraction, small angle X-ray scattering, and electron microscopy analyses revealed that the PAN phase in the fiber existed as an elongated island owing to the large draft force used on the spinning solutions. The PAN phase in the fiber was removed with dimethyl sulfoxide to obtain neat Cell fibers with elongated pores and nanometer-sized cross-sections. The generated pores, acting as starting points for fibrillation, allowed the lateral cohesion of the fibers to be weakened and facilitated the fibrillation tendency. Cell fibers regenerated from a 100/20 weight ratio blend of Cell/PAN were easily fibrillated to microfibrils with an average diameter of 114 ± 67 nm by mechanical treatment.Graphical abstract: [ABSTRACT FROM AUTHOR]

Cellulose/aromatic polysulfonamide (PSA) blended fibers with good flame-retardant, hydrophilic and mechanical properties were successfully prepared by dry-jet wet spinning technology with 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) as solvent. The solution behaviors were studied using the polarized light microscopy (PLM) and rheology measurements. PLM images showed that both cellulose and PSA dissolved completely in solvent. The viscosity of the blend solutions decreased with increasing ratio of PSA. While comparing the experimental results with the calculated data according to the log-additivity rule, it is revealed that zero-shear viscosity shows positive deviations, which indicates a strong interaction between cellulose and PSA. The flame retardant properties of the blended fibers were characterized. When the content of PSA is 70 wt% in the blended fibers, the limiting oxygen index (LOI) is up to 26.2% and the self-extinguishing time away from the flame is just 2 s. The blended fibers exhibited good mechanical properties with the tenacity of 2.6 cN/dtex and the E-modulus of 34.2 cN/dtex, which were higher than that of the washed PSA fiber. The contact angle of the blended fibers containing 70 wt% PSA was 64°, as was smaller than the value of PSA fiber. The morphology and structure of the blended fibers were characterized by scanning electron microscope (SEM), laser scanning confocal microscope (LSCM) and X-ray diffraction (XRD). The SEM images showed a rough morphology for the blended fibers. From the LSCM images, a sheath-core morphology was observed in the blended fibers with 70 wt% PSA. Only cellulose II crystalline structure of the blended fibers was observed from the XRD patterns because no crystallization occurred in PSA phase without heat-stretching and heat-setting at high temperature. This work provides a simple and effective way to prepare flame-retardant fibers with improved hydrophilic and mechanical properties. [ABSTRACT FROM AUTHOR]

N-Methylmorpholine- N-oxide (NMMO) cannot be completely separated by extraction from mixtures with common 1,3-dialkylimidazolium ionic liquids (ILs) due to strong ionic interactions between the two components. At elevated temperatures, above approx. 90 °C, especially under dry conditions and in the presence of acid, alkylating or acylating agents, remaining NMMO in ILs tends to undergo autocatalytic degradation. This is a highly exothermic, unstoppable process that results in explosions, flames, and complete charring of the reaction mixtures. Thus, caution must be exercised when drying or heating ILs that were in previous contact with NMMO, and the absence of amine oxide must be confirmed to avoid potential danger. [ABSTRACT FROM AUTHOR]

The effect of alkyl chain length on the wetting properties of alkyltrichlorosilane coated cellulose-based paper is reported for four different reagents: methyltrichlorosilane (MTCS; -CH), butyltrichlorosilane (BTCS; -CH), dodecyltrichlorosilane (DTCS; -CH) and octadecyltrichlorosilane (OTCS; -CH). SEM analysis reveals that by systematically varying alkyl chain length, films with different surface morphologies can be generated on flat silicon wafer control samples and on cellulose-based paper samples. The variation in surface morphology leads to different wetting behavior, as determined by measuring static water and oil contact angles. Due to the nano- and micron- scale roughness on MTCS coated substrates, paper samples coated with MTCS display superhydrophobicity with a water contact angle of 152.2°, which is the highest water contact angle among these four alkyltrichlorosilanes. However, additional nano-scale roughness from MTCS coating reduces the oil resistance of coated paper samples, while paper samples coated with long-chain alkyltrichlorosilanes have lower surface energy and also lack nano-scale roughness. As a result, paper samples coated with OTCS display the highest resistance against oils (ethylene glycol contact angle 125.5°; diiodomethane contact angle 101.3°). The intrinsic porosity of paper is largely retained after coating, as indicated by the fact that low surface tension fluids like methanol can easily penetrate coated paper samples. [ABSTRACT FROM AUTHOR]