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Multifunctional cellulosic fibers are in high demand for use in a variety of applications. Functional cellulosic fibers obtained through green and sustainable approaches are getting special attention because of the need to limit the environmental impact of hazardous chemicals. Herein, a novel facile, efficient, and eco-friendly approach for multifunctional viscose fibers@Ag NPs (VF-Ag) was designed by a rapid, facile, and one-pot biosynthesis green route using guava leaf extract as a reducing and stabilizing agent. UV–Vis, TEM, SEM, EDX, FTIR, and XPS were used to analyze the formation of silver nanoparticles and their subsequent deposition on the surface of viscose fibers. The silver nanoparticles immobilized on the surface of viscose fibers endowed a yellow/brownish color to the fibers as well as improving the dyeing with reactive dye. The VF-Ag samples have multifunctional properties like protective activities against UV radiation and microorganisms, antioxidant activity, and sensor ability toward Hg2+. The results demonstrated that the UPF values of VF-Ag samples ranged from 280 to 355 compared to 103 for VF. The antioxidant activities of VF-Ag ranged from 79 to 85% compared to 9% for VF. VF-Ag samples exhibited excellent antimicrobial activities against Gram-positive and Gram-negative bacteria, very good activities against yeast, and low activities against fungus. VF and VF-Ag were dyed using reactive dye (CI-reactive blue-19) at two color intensities (2.5, and 5%). The results show that the color of VF turned blue, while the color of VF-Ag turned greenish. The color strength of VF-Ag significantly increased with increasing silver content. Furthermore, VF-Ag showed high sensitivity to naked-eye colorimetric sensing for the detection of Hg2+. In straightforward, this innovative approach provides an easy, quick, and low-cost that will open the door for a range of versatile applications for modified viscose fibers in the fields of medical and analytical applications. [ABSTRACT FROM AUTHOR]

Due to its exceptional sensitivity and conductivity, flexible wearable sensors have received a lot of interest recently in the fields of human health monitoring and motion detection. In this work, a superhydrophobic and extremely permeable pressure sensor using multilayer hydroentanglement cellulose non-woven fabrics modified with carbon nanotubes was prepared by ultrasonic-assisted modification and impregnation. The sensor has high sensitivity (11.78 kPa-1 in 0-5.20 kPa and 0.058 kPa-1 in 5.20-210 kPa), fast response time (49 ms), ultra-wide pressure detection range (0–210 kPa), excellent air permeability (688 mm/s) and long-term reliability. With a 155° water contact angle, it also exhibits exceptional superhydrophobic characteristics, providing an outstanding self-cleaning effect. Importantly, the sensor has been successfully applied to monitor weak movements (pulse, voice recognition) and joint movements in real-time, which has paved the way for human health monitoring and disease diagnosis. In addition, using the superhydrophobicity and sensitivity of the sensor, it can be connected to a mobile phone via Bluetooth for remote real-time monitoring and applied to drowning alarm monitoring in underwater environments, showing great promise in practical applications. [ABSTRACT FROM AUTHOR]

To effectively remove pharmaceuticals, nitroaromatic compounds, and dyes from wastewater, an efficient multifunctional material was created based on silver nanoparticles (Ag) and MIL-125-NH2 (MOF) immobilized on viscose fibers (VF) as a support substrate. Firstly, silver nanoparticles (Ag) were immobilized on the surface of viscose fibers (VF) via in situ synthesis using trisodium citrate (TSC) as a reducing agent to create (VF-Ag). Then, VF and VF-Ag were decorated with the titanium metal–organic framework MIL-125-NH2 (MOF) to create VF-MOF and VF-Ag-MOF. The influence of VF-Ag, VF-MOF, and VF-Ag-MOF on the sonocatalytic or sonophotocatalytic degradation of sulfa drugs was investigated. The results show that VF-Ag-MOF showed excellent sonocatalytic and sonophotocatalytic activity towards the degradation of sulfa drugs compared to VF-Ag and VF-MOF. Furthermore, sonophotodegradation showed a dramatic enhancement in the efficiency of degradation of sulfa drugs compared to sonodegradation. The sonophotodegradation degradation percentage of sulfanilamide, sulfadiazine, and sulfamethazine drugs in the presence of VF-Ag-MOF was 65, 90, and 95 after 45 min of ultrasonic and visible light irradiation. The catalytic activity of VF-Ag, VF-MOF, and VF-Ag-MOF was evaluated through the conversion of p-nitrophenol (4-NP) to p-aminophenol (4-AP). The results demonstrate that VF-Ag-MOF had the highest catalytic activity, followed by VF-Ag and VF-MOF. The conversion percentage of 4-NP to 4-AP was 69%. The catalytic or photocatalytic effects of VF-Ag, VF-MOF, and VF-Ag-MOF on the elimination of methylene blue (MB) dye were investigated. The results demonstrate that VF-Ag-MOF showed high efficiency in removing the MB dye through the reduction (65%) or photodegradation (71%) after 60 min. VF-Ag-MOF composites structure–activity relationships represent that doping within silver NPs enhanced the photocatalytic activity of MIL-125-NH2, which could be explained as follows: (i) Due to the formation of a Schottky barrier at the junction between MIL-125-NH2 and Ag NPs, the photogenerated electrons in the conduction band of MIL-125-NH2 were supposed to be quickly transferred to the valence band of the Ag NPs, and subsequently, the electrons were transferred to the conduction band of Ag NPs. This considerable electron transferring process, which is reported as Z scheme heterojunction, can efficiently suppress the recombination of electron/hole pairs in VF-Ag-MIL-125-NH2 composites. (ii) Sufficient separation between the photogenerated charge carriers (holes and electrons) and avoiding their recombination enhanced the photocatalytic activity of composites. [ABSTRACT FROM AUTHOR]

The self-adaptive nature of smart textiles to the ambient environment has made them an indispensable part of emerging wearable technologies. However, current advances generally suffer from complex material preparation, uncomfortable fitting feeling, possible toxicity, and high cost in fabrication, which hinder the real-world application of smart materials in textiles. Herein, humidity-response torsional and tensile yarn actuators from twisted and coiled structures are developed using commercially available, cost-effective, and biodegradable viscose fibers based on yarn-spinning and weaving technologies. The twisted yarn shows a reversible torsional stroke of 1400° cm−1 in 5 s when stimulated by water fog with a spraying speed of 0.05 g s−1; the coiled yarn exhibits a peak tensile stroke of 900% upon enhancing the relative humidity. Further, textile manufacturing allows for the scalable fabrication to create fabric artificial muscles with high-dimensional actuation deformations and human-touch comfort, which can boost the potential applications of the humidly adaptive yarns in smart textile and advanced textile materials. [ABSTRACT FROM AUTHOR]

Activated carbons derived from viscose fibers were prepared using potassium hydroxide, carbon dioxide, or water vapor as activation agents. The produced activated carbon fibers were analyzed via scanning electron microscopy and energy dispersive X-ray spectroscopy, and their porosity (specific surface area, total pore volume, and pore size distribution) was calculated employing physisorption experiments. Activated carbon fibers with a specific surface area of more than 2500 m2 g−1 were obtained by each of the three methods. Afterwards, the suitability of these materials as electrodes for electrochemical double-layer capacitors (supercapacitors) was investigated using cyclic voltammetry, galvanostatic measurements, and electrochemical impedance spectroscopy. By combining CO2 and H2O activation, activated carbon fibers of high purity and excellent electrochemical performance could be obtained. A specific capacitance per electrode of up to 180 F g−1 was found. In addition, an energy density per double-layer capacitor of 42 W h kg−1 was achieved. These results demonstrate the outstanding electrochemical properties of viscose-based activated carbon fibers for use as electrode materials in energy storage devices such as supercapacitors. [ABSTRACT FROM AUTHOR]

The self-adaptive nature of smart textiles to the ambient environment has made them an indispensable part of emerging wearable technologies. However, current advances generally suffer from complex material preparation, uncomfortable fitting feeling, possible toxicity, and high cost in fabrication, which hinder the real-world application of smart materials in textiles. Herein, humidity-response torsional and tensile yarn actuators from twisted and coiled structures are developed using commercially available, cost-effective, and biodegradable viscose fibers based on yarn-spinning and weaving technologies. The twisted yarn shows a reversible torsional stroke of 1400° cm−1 in 5 s when stimulated by water fog with a spraying speed of 0.05 g s−1; the coiled yarn exhibits a peak tensile stroke of 900% upon enhancing the relative humidity. Further, textile manufacturing allows for the scalable fabrication to create fabric artificial muscles with high-dimensional actuation deformations and human-touch comfort, which can boost the potential applications of the humidly adaptive yarns in smart textile and advanced textile materials.

Bio-based, renewable and biodegradable products with multifunctional properties are also becoming basic trends in the textile sector. In this frame, cellulose nanofibrils (CNFs) have been surface modified with hexamethylenediamine/HMDA and used as an antimicrobial additive to a ring-spun viscose yarn. The CNF-HMDA suspension was first characterized in relation to its skin irritation potential, antimicrobial properties, and technical performance (dispersability and suspensability in different media) to optimize its sprayability on a viscose fiber sliver with the lowest sticking, thus to enable its spinning without flowing and tearing problems. The impact of CNF-HMDA content has been examined on the yarn's fineness, tensile strength, surface chemistry, wettability and antimicrobial properties. The yarn's antimicrobial properties were increasing with the content of CNF-HMDA, given a 99% reduction for S. aureus and C. albicans (log 1.6–2.1) in up to 3 h of exposure at minimum 33 mg/g, and for E. coli (log 0.69–2.95) at 100 mg/g of its addition, yielding 45–21% of bactericidal efficacy. Such an effect is related to homogeneously distributed CNF-HMDA when sprayed from a fast-evaporated bi-polar medium and using small (0.4 mm) nozzle opennings, thus giving a high positive charge (0.663 mmol/g) without affecting the yarn's tenacity and fineness, but improving its wettability. However, a non-ionic surfactant being used in the durability testing of functionalized yarn to 10-washing cycles, adheres onto it hydrophobically via the methylene chain of the HMDA, thus blocking its amino groups, and, as such, decreasing its antibacterial efficiency, which was slightly affected in the case when the washing was carried out without using it. [ABSTRACT FROM AUTHOR]

A novel fiber-based biosorbent for dyes removal and microbial inactivation was prepared by enzymatic oxidization of viscose fibers and further modification with ε-polylysine. Glucose oxidase (GOx) was first employed as the enzyme for oxidation of viscose fibers. The consequences illustrated that the hydroxyl group on C1 position of viscose fibers was successfully oxidized with oxidation ratio of 2.43 ± 0.31%. Subsequently, ε-polylysine with average molecular weight of 4.44 ± 1.13 KDa and antimicrobial activity to E. coli of 90.48 ± 1.64 was modified with oxidized viscose fibers by lipase. Experimental results showed that oxidized viscose fibers were successfully modified with ε-polylysine with optimum degree of modification (DM) of 13.56 ± 1.05%. This oxidized viscose fiber modified with ε-polylysine (OVF-PL) displayed good dyes adsorption (or dyes removal) capacity for both anionic and cationic dyes, especially for anion dyes. Furthermore, OVF-PL showed excellent antimicrobial activity against E. coli and B. subtilis, particularly for E. coli , with GIB of 92.65%. Such fiber-based may offer a new pathway for preparing economical and efficient biosorbent for environmental remedy purpose. • Enzymatic oxidization of viscose fibers was proposed. • A novel fiber-based biosorbent modified with ε-polylysine (OVF-PL) was prepared. • OVF-PL shows excellent dyes removal capacity and microbial inactivation. [ABSTRACT FROM AUTHOR]

Activated carbons derived from viscose fibers were prepared using potassium hydroxide, carbon dioxide, or water vapor as activation agents. The produced activated carbon fibers were analyzed via scanning electron microscopy and energy dispersive X-ray spectroscopy, and their porosity (specific surface area, total pore volume, and pore size distribution) was calculated employing physisorption experiments. Activated carbon fibers with a specific surface area of more than 2500 m2 g−1 were obtained by each of the three methods. Afterwards, the suitability of these materials as electrodes for electrochemical double-layer capacitors (supercapacitors) was investigated using cyclic voltammetry, galvanostatic measurements, and electrochemical impedance spectroscopy. By combining CO2 and H2O activation, activated carbon fibers of high purity and excellent electrochemical performance could be obtained. A specific capacitance per electrode of up to 180 F g−1 was found. In addition, an energy density per double-layer capacitor of 42 W h kg−1 was achieved. These results demonstrate the outstanding electrochemical properties of viscose-based activated carbon fibers for use as electrode materials in energy storage devices such as supercapacitors.

The development of high-performance fabrics/fibers using green chemistry is a formidable challenge. Natural plant extracts are attracting increasing interest for use in the production of sustainable textile surfaces with a wide range of functional properties and environmental benefits. Peanut red skin, as a byproduct of the peanut industry, is abundant, inexpensive, and readily available. Peanut red skin is a rich source of bioactive compounds but has a low economic value. The current study presents a new sustainable and ecofriendly approach to imparting textiles with multifunctional properties using the extract of peanut red skin. This approach included two steps. The first step was aimed to evaluate the effect of different solvents such as water, ethanol, and hexane on the phytochemical and volatile compounds extracted from peanut red skin using microwave heating to select the best solvent for extraction of bioactive compounds from peanut red skin. The second step was focused on the feasibility of dyeing viscose fibers or simultaneously dyeing and incorporating silver nanoparticles (Ag NPs) onto viscose fibers using the aqueous extract of peanut red skin. HS–GC–MS analysis showed a substantial variation in the concentrations of the components depending on the extraction solvent. The aqueous extract had the highest total yield (7.9%), total phenolic content (76.4 ± 1.07 mg/100 mL), total flavonoid content (31.6 ± 1.12 mg/100 mL), and antioxidant activity (88 ± 2.15%). Analysis of the aqueous extract using high-performance liquid chromatography revealed the existence of 21 natural compounds, including 14 phenolic compounds and 7 flavonoid compounds. Subsequently, viscose fibers simultaneously dyed and incorporation with Ag NPs through an in situ green synthesis showed excellent antimicrobial activities against different microorganisms and high antioxidant activity, as well as good UV protection. [ABSTRACT FROM AUTHOR]

In order to replace the synthetic pigment and broaden the application of capsicum red pigment in dyeing and finishing, the edible pigment capsanthin is mordantly dyed on viscose fibers, and then fixed by zein. The effects of mordant types and mordant dyeing methods on fabric dyeing properties were compared. The effects of mordant dyeing time, temperature, mordant dosage and pH value on fabric mordant dyeing properties were discussed, and the dyeing process was optimized. It compared the color fastness of fabrics before and after fixing with zein. The results showed that using aluminum sulfate as mordant in the same bath mordant dyeing could obtain deep color fabrics, and the optimal dyeing conditions were as follows: mordant dyeing time was about 45 min, temperature was 80 °C, aluminum sulfate dosage was 4.0% (owf), and pH value was 4.0. The dyed fabric has deep color and certain rubbing fastness and soaping fastness, but the color change fastness cannot meet the actual demand. After zein treatment, the color of the fabric is not affected, and the soaping fastness of the fabric is improved by 3-4 grades. [ABSTRACT FROM AUTHOR]

Multifunctional fibrous surfaces with ultraviolet protection, self-cleaning, or antibacterial activity have been highly attractive. Nanocomposites consisting of silver (AgNPs) and titanium dioxide (TiO2 NPs) nanoparticles (Ag/TiO2) were developed and coated onto the surface of viscose fibers employing a straightforward pad–dry–cure procedure. The morphologies and elemental compositions were evaluated by scan electron microscopy (SEM), infrared spectra (FTIR), and energy-dispersion X-ray spectra (EDS). The resultant multifunctional textile materials displayed antibacterial and photo-induced catalytic properties. The photocatalyzed self-cleaning properties were investigated employing the photochemical decay of methylthioninium chloride, whereas the antibacterial properties were studied versus E. coli. The viscose fibers coated with Ag/TiO2 nanocomposite demonstrated improved efficiency compared with viscose fibers coated with pure anatase TiO2 nano-scaled particles.

Exposure to different arsenic concentrations (higher than 10 μg/L), either due to the direct consumption of contaminated drinking water or indirectly by using contaminated food is harmful for human health. Therefore, it is important to remove arsenic from aqueous solutions. Among many arsenic removal technologies, adsorption offers a promising solution with a good efficiency, however the material used as adsorbent play a very vital role. The present investigation evaluated the behavior of two cellulose-based adsorbent materials, i.e., viscose fibers (V) and its TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) derivative, obtained by using the well-established TEMPO-mediated protocol (VF). Due to the known arsenic affinity for Fe ions the two materials were later doped with it. This was done after a preliminary functionalization with di-2-ethylhexyl phosphoric acid (DEHPA), to obtain two materials: V-DEHPA-Fe and VF-DEHPA-Fe. Arsenic adsorption is known to be pH dependent (between 6 and 8); therefore, the optimal pH range for As(V) adsorption has been established. In order to evaluate the adsorption mechanism for both the synthesized materials, the influence of contact time, temperature and initial concentration was evaluated. Langmuir, Freundlich and Sips equilibrium isotherm models were used in order to determine the ability of the model to describe As(V) adsorption process. The maximum adsorption capacity of the material V-DEHPA-Fe was 247.5 µg As(V)/g with an As(V) initial concentration of 5 mg/L and for the material VF-DEHPA-Fe it was 171.2 µg As(V)/g with initial concentration of 5 mg/L.

Viscose fibers (VFs) modified with silkworm pupa chitosan oligosaccharide (SPCOS) by β -glucosaccharase were prepared in this study. Silkworm pupa underwent the processes of deproteinization, demineralization, decoloration and depolymerization. SPCOS with a DD of 91.64 ± 0.86% and Mw of (2.56 ± 0.15) × 104 g/mol was prepared. The prepared SPCOS was used for the modification of VFs. β -glucosaccharase was used as the enzyme for this modification. The results showed that VFs were successfully modified with SPCOS by β -glucosaccharase. The synthesized VFs modified with SPCOS (VF-SPCOS) were dyed more steadily by anionic dyes than cationic dyes. Furthermore, VF-SPCOS showed a good antibacterial property against E. coli and S. aureus, especially to E. coli. In the reuse study of SPCOS, the antibacterial property to E. coli of VF-SPCOS was still retained at 87.68 ± 1.18% of its initial value after the 12th reuse of SPCOS. [ABSTRACT FROM AUTHOR]

Viscose fibers were impregnated with different concentrations of diammonium hydrogen phosphate (DAHP), carbonized, activated, and tested as high-performance electrode materials for supercapacitors. The yield of these activated carbon fibers (ACFs) could be increased by a factor of 14 by using DAHP compared to ACF without impregnation. These specific activation procedures yielded a high specific surface area of more than 2700 m2·g−1 with a pore size distribution (PSD) suitable for use as a supercapacitor electrode. The electrode materials were implemented in symmetric supercapacitors using TEMA BF4 as electrolyte and cyclic voltammetry measurements showed high specific capacitances of up to 167 F·g−1. Furthermore, the devices showed high energy densities of up to 21.4 W·h·kg−1 and high-power densities of up to 8.7 kW·kg−1. The supercapacitors featured high capacity retention (96%) after 10,000 cycles. These results show that ACFs made of viscose fibers, previously impregnated with DAHP, can be used as high-performance electrodes in supercapacitors for energy storage applications.

In situ synthesis of Ag/AgX nanoparticles (NPs) onto viscose fibers adds new functionalities and broadens their applications. In this study, Ag/AgX (X = Cl, I) NPs were in situ synthesized onto viscose fibers to impart brilliant colors, UV-protection, antimicrobial, self-cleaning, and photocatalytic properties. The AgX NPs were deposited on the fibers by ultrasonic irradiation, while Ag-NPs were formed by photoreduction of excess Ag + ions under UV irradiation. The Ag/AgX NPs-loaded onto viscose fibers endowed with pale yellow for Ag/AgI and pale purple/violet for Ag/AgCl. The colored viscose fibers showed excellent antimicrobial activity against Escherichia coli (gram-negative), Staphylococcus aureus (Gram positive), and Candida Albican . The Ag/AgX/viscose fiber also showed excellent photocatalytic and self-cleaning activity toward degradation of methylene blue. [ABSTRACT FROM AUTHOR]

Lyocell fiber has emerged as an important class of regenerated cellulose that is produced based on the N-methyl morpholine-N-oxide (NMMO) dissolution method, and it has unique properties compared to viscose fiber. The NMMO technology provides a simple, resource-conserving, and environmentally friendly method for producing regenerated cellulose fiber. In this paper, the manufacturing process, environmental impact, and product quality of lyocell fiber are reviewed and compared with those of the conventional viscose fiber. [ABSTRACT FROM AUTHOR]

Viscose fiber (VIF) burns easily, bio-based carrageenan fiber (CAF) is inherently flame retardant. Can the addition of carrageenan fibers improve the flame retardant properties of VIF/CAF blended materials? In this study, VIF/CAF papers were successfully prepared in a green way without any pollution. The thermal degradation properties and flame retardancy of VIF/CAF papers were tested by thermogravimetric analysis, limiting oxygen index test, flammability test and cone calorimeter test. The results showed that the introduction of carrageenan fibers significantly changed the thermal stability and flame retardancy of VIF/CAF papers. Moreover, the addition of carrageenan fibers obviously increased the mechanical strength of the VIF/CAF papers. [ABSTRACT FROM AUTHOR]

This work was sparked by the reported identification of man-made cellulosic fibers (rayon/viscose) in the marine environment as a major fraction of plastic litter by Fourier transform infrared (FT-IR) transmission spectroscopy and library search. To assess the plausibility of such findings, both natural and man-made fibers were examined using FT-IR spectroscopy. Spectra acquired by transmission microscopy, attenuated total reflection (ATR) microscopy, and ATR spectroscopy were compared. Library search was employed and results show significant differences in the identification rate depending on the acquisition method of the spectra. Careful selection of search parameters and the choice of spectra acquisition method were found to be essential for optimization of the library search results. When using transmission spectra of fibers and ATR libraries it was not possible to differentiate between man-made and natural fibers. Successful differentiation of natural and man-made cellulosic fibers has been achieved for FT-IR spectra acquired by ATR microscopy and ATR spectroscopy, and application of ATR libraries. As an alternative, chemometric methods such as unsupervised hierarchical cluster analysis, principal component analysis, and partial least squares-discriminant analysis were employed to facilitate identification based on intrinsic relationships of sample spectra and successful discrimination of the fiber type could be achieved. Differences in the ATR spectra depending on the internal reflection element (Ge versus diamond) were observed as expected; however, these did not impair correct classification by chemometric analysis. Moreover, the effects of different levels of humidity on the IR spectra of natural and man-made fibers were investigated, too. It has been found that drying and re-humidification leads to intensity changes of absorption bands of the carbohydrate backbone, but does not impair the identification of the fiber type by library search or cluster analysis. [ABSTRACT FROM AUTHOR]

In the current approach, the microwave heating and polyol method are applied for first time to facilitate silver nanoparticles (Ag NPs) in-situ incorporated into viscose fibers. The Ag NPs gave a distinctive color as well as multifunctional properties to viscose fibers. The Ag + ions in the viscose fiber surfaces are reduced to Ag NPs with ethylene glycol as reducing agent and polyvinylpyrrolidone (PVP) as stabilizing agent. This takes less period and energy than that consumed during the conventional heating method (exo-situ incorporated). The silver nanoparticles were examined through UV–Vis spectrum of the residual solutions and transmission electron microscopy (TEM). The Ag NPs incorporated viscose fiber surfaces were characterized by using scanning electron microscopy coupled with an energy dispersive spectrometer (SEM-EDX), Fourier transform infrared spectroscopy (FTIR), and thermo-gravimetric analysis (TGA) measurements. The effects of silver nanoparticles on the multifunctional properties of the fibers including coloration, antibacterial activity and catalytic properties were evaluated. The overall results point out that, the Ag NPs incorporated viscose fibers exhibited excellent color fastness as well as good antibacterial and catalytic properties. In straightforward, the procedure adopted for fabricating these multifunctional viscose fibers is environmental friendly beside time and energy-saving. [ABSTRACT FROM AUTHOR]

The fact that cellulose materials soften with water uptake is exploited constantly during paper production to form strong bonds between two fibers. Here, we present measurements of surface hardness and reduced modulus of viscose fibers by atomic force microscopy based nanoindentation at varying relative humidity. A home-built setup allowed to access a wide humidity range from 5 % until 95 % relative humidity. The obtained results are compared to those of softwood kraft pulp fibers. Creep effects at a constant load during indentation were observed and found to increase exponentially with increasing humidity. In order to relate mechanical properties to the water content within a fiber, also gravimetric sorption studies were performed. This allowed to extrapolate the mechanical properties of viscose fibers to 100 % relative humidity. Interestingly, hardness and reduced modulus are at this point higher by a factor of 4 and 20, respectively, compared to those of viscose fibers fully swollen in water. Pulp fibers, in comparison, exhibit mechanical properties which are similar to those of viscose fibers. Only when the fibers are swollen, a higher hardness for viscose fibers is evident, whereas the moduli of pulp and viscose fibers are still comparable. [ABSTRACT FROM AUTHOR]

Application of size exclusion chromatography (SEC) for the analysis of cellulose samples is often limited due to poor solubility in the solvent system N, N-dimethylacetamide/lithium chloride (DMAc/LiCl). Hence different activation or derivatization methods have been developed and published. Most of these methods are laborious, influence the molar mass distribution or do not support dissolution of manmade fibers, such as viscose rayon. In this study, we have evaluated different activation methods for their applicability in viscose rayon dissolution and we present a novel method for activation. We found that an additional solvent exchange step with dimethyl sulfoxide (DMSO) increases and accelerates solubility of viscose fibers in DMAc/LiCl for subsequent SEC analysis. The improved dissolution by DMSO activation is mainly due to increased swelling and improved action towards the outer skin of the fiber. The novel approach has also been applied to the even more difficult dissolution of oxidized viscose fibers. [ABSTRACT FROM AUTHOR]

The oxidized sodium carboxymethylcellulose (O-CMC) fibers have been successfully synthesized via the oxidation-etherification method. Subsequently, the O-CMC fibers are characterized by Fourier transform infrared (FT-IR), C nuclear magnetic resonance (C-NMR) and X-ray diffraction (XRD). In addition, the viscosity behaviors of the O-CMC aqueous solution have been investigated at five temperatures (25, 30, 40, 50 and 60 °C), six concentrations (30, 35, 40, 45, 50 and 60 kg/m) and four shear rates (6, 12, 30 and 60 rpm). The results show that the viscosity of the O-CMC aqueous solution increases with increasing concentrations and decreases with increasing temperature. The viscosity of the O-CMC aqueous solution is found to exhibit a dilatant behavior. The dissolution rate in water of the O-CMC fibers is faster than that of the carboxymethylcellulose (CMC) fibers. It could be used as novel absorbable hemostatic fibers in surgery. [ABSTRACT FROM AUTHOR]

Regenerated cellulose fibers-viscose fibers-were coated with chitosan using an ultrasound technique to improve their accessibility, reactivity and sorption properties. The main purpose of our research was to study the modification of viscose fibers and to determine the effect of the application of chitosan onto viscose fibers. Samples were obtained by treating the fibers with chitosan in a dilute acetic acid solution in an ultrasonic bath. The influences of the chitosan coating on the changes in morphology, supramolecular structure, sorption and tensile properties were studied. The spectra (FTIR analysis) of the treated viscose fibers showed changes and new absorption bands that revealed the existence of the chemical interactions with the chitosan. The scanning electron microscope images confirmed that the surface of the fibers was covered with the chitosan. A decrease in the water retention value and increase in the absorption and moisture content with an increasing concentration of chitosan was noted. Furthermore, the differences in tensile behavior were analyzed using an Instron tensile testing machine. The chitosan coating had no effect on the tensile strength of the viscose fibers, but influenced the tensile strain. Some changes, though not significant, were noted in the structure (crystallinity, orientation) of the treated viscose fibers. [ABSTRACT FROM AUTHOR]

Abstract: Regenerated cellulose fibers, type viscose, have been oxidized with sodium hypochlorite and catalytic amounts of sodium bromide by using two different protocols: first, involving the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and second, employing N-hydroxyphthalimide (NHPI). The reactions were carried out at room temperature and pH=10.5 for 2.5h. Viscose oxidized samples were analyzed and compared in terms of the negative charged groups content, as determined by potentiometric titration and methylene blue adsorption, morphologies and crystallinities changes, as well as changes in the degree of polymerization. The highest content of the carboxylic groups and the best preservation of the morphology and molecular weight of the original material have been found in the case of using NHPI/anthraquinone as oxidation mediators. TEMPO-mediated oxidation leads to the highest depolymerization and cause significant degradation of the cellulosic material. [Copyright &y& Elsevier]

Abstract: NHPI (N-hydroxyphthalimide) was used to mediate the oxidation of cellulose fibers in the absence of sodium bromide, as traditionally was used in this kind of transformations, solely using sodium hypochlorite (NaOCl) as the primary oxidant. Avoiding the use of NaBr is highly desired from both environmental and corrosion concerns. The non-persistent PINO (phthalimide-N-oxy) radical, the key species in the oxidation reaction, has been in situ generated from NHPI and copper (II) chloride. The reaction was performed at room temperature at pH=10.5. The carboxylic moiety formation was evidenced by FTIR and X-ray photoelectronic spectroscopy (XPS) and the content of the negatively charged groups determined by potentiometric titration. The changes appeared in crystallinity were evidenced by X-ray diffraction technique. [Copyright &y& Elsevier]

The solutions of wool keratin with different molecular weight were prepared by reduction method. The results of fourier transform infrared( FT-IR) indicated that the molecular structure of keratin had little change, the integrality of the keratin macro-molecules was kept unchanged, but the S-S bond and -OH bond were broken. The keratin viscose fibers were prepared through surface grafting method. The morphology, surface structure and mechanical properties of keratin viscose fibers were studied. The surface of viscose fibers was covered with keratin, and the wet strength was improved. [ABSTRACT FROM AUTHOR]

Carboxymethylcellulose (CMC) fibers have been successfully prepared from viscose fibers through the process of alkalization-etherification. Parameters including reaction temperature, mass ratio of NaOH to the viscose fibers, and mass ratio of the viscose fibers to ethanol are studied. The degree of substitution (DS) and the inherent viscosity of the CMC fibers are determined. The CMC fibers are characterized by using Fourier transform infrared spectroscopy (FT-IR), H-nuclear magnetic resonance spectroscopy (H-NMR), scanning electron microscopy (SEM), and the X-ray diffraction (XRD). The analysis demonstrates that under the experimental conditions where the reaction temperature is 40 °C, mass ratio of NaOH to the viscose fibers is 2.0, and mass ratio of the viscose fibers to ethanol is 1:15, the obtained CMC fibers possess an appropriate DS, better water-solubility, and lower degree of etching, thus they can be used as absorbable hemostatic fibers. [ABSTRACT FROM AUTHOR]

The development of efficient process steps to convert paper-grade to dissolving pulps was investigated as part of the work programme to improve the process economics. The challenge of pulp refinement comprises the selective removal of hemicelluloses and the precise adjustment of the pulp viscosity, while maintaining the reactivity of the pulp as required for viscose application. The purpose of this study was to investigate the effects of various enzyme treatments on a commercial oxygen-delignified Eucalyptus globulus paper-grade kraft pulp in the course of a total chlorine free bleaching sequence in combination with refining techniques following the principle of Modified Kraft Cooking (Sixta et al. ). The objectives were to assess its applicability as viscose pulp besides the reduction of chemical consumption in alkaline and ozone bleaching steps by means of xylanase pre-treatment and the controlled adjustment of final pulp viscosity utilizing endoglucanase post-treatment. Xylanase pre-treatment combined with cold caustic extraction at reduced alkalinity efficiently removed the hemicelluloses from the pulp and clearly increased the pulp brightness by extensive removal of hexenuronic acid side chains. The xylanase pre-treated pulp showed increased reactivity towards xanthation and high viscose dope quality in terms of particle content. The dependence of cellulose chain scission on the applied endoglucanase concentration was analyzed in detail, and this allowed precise viscosity reduction as well as reactivity increase. The differently treated pulps, with and without xylanase pre-treatment, were of very narrow molecular weight distribution and the quality of the spun fibers were very similar to those viscose fibers from commercial dissolving pulps. [ABSTRACT FROM AUTHOR]

Two types of regenerate cellulose fibres were oxidized under mild conditions, by using Nhydroxyphthalimide as catalyst and molecular oxygen as ultimate oxidizing agent. The amounts of negatively charged groups introduced were determined by means of potentiometric titration. The degree of polymerization and molar mass of the oxidized fibres determined viscosimetrically, has been found to be almost unaffected during oxidation. [ABSTRACT FROM AUTHOR]

Presently polycarboxylic acids are being used for cellulose crosslinking. Among these, 1,2,3,4-buthanetetracarboxylic acid (BTCA) is the most effective in combination with a corresponding catalyst. In this research, a comparison of crosslinking effects on mercerized cotton fibers and viscose was identified using certain physical--chemical methods. The extent of crosslinking was evaluated using Fourier transform infrared (FT-IR) spectroscopy. The crosslinking of cellulose increases wrinkle resistance and reduces the mechanical properties, therefore, for this purpose the wrinkle recovery angle and the breaking force, was evaluated together with breaking elongation. When considering the crosslinking mechanism, those additional free BTCA carboxyl groups that are accessible in the cellulose polymer reflect the effectiveness of cotton-fiber crosslinking. The evaluation of accessible carboxyl was performed using the methylene blue method, where the adsorption of methylene blue dye on the cellulose material was monitored spectroscopically. The purpose of this research is mainly (i) to evaluate how different types of cellulose matrices/substrates influence the crosslinking of fibers crosslinked with different mass fractions of BTCA and (ii) to establish the most appropriate mass fraction of BTCA in the impregnation bath for sufficient crosslinking of mercerized cotton fibers, as well as viscose. [ABSTRACT FROM AUTHOR]

Viscose fibers (regenerated cellulose), were drawn using a stress-strain device, in conjunction with a two beam interferometric system. A recent approach is applied for determining the unknown initial value for a given viscose fiber. Optical and mechanical parameters were measured. The results were used to calculate the crystallinity, amorphous, and crystalline orientations functions. Calculation of the crosslink density and the chain entanglement density with the aid of Moony-Rivlin equation constants were given. Also, some other optical and mechanical structure parameters were given. An empirical formula is suggested for the results parameter changes. The present study throws light on the changes due to cold drawing processes for viscose fibers. [ABSTRACT FROM AUTHOR]

Two kinds of water-soluble metallophthalocyanines, binuclear cobalt phthalocyanine (Co2Pc2) and binuclear ferric phthalocyanine (Fe2Pc2), were synthesized through phenylanhydride-urea route and characterized by elemental analysis and FT-IR spectra. Binuclear metallophthalocyanine derivatives (Mt2Pc2) were immobilized on silk fibers and modified viscose fibers to construct bioactive fibers of mimic enzyme. Mt2Pc2 was used as the active center of bioactive fibers, viscose and silk fibers as the microenvironments. The catalytic oxidation ability of bioactive fibers on the malodors of methanthiol and hydrogen sulfide was investigated at room temperature. The experimental results indicated that the catalytic activity of such bioactive fibers was closely correlative to the types of bioactive fibers and substrates. [ABSTRACT FROM AUTHOR]

The purpose of the present investigation is to study the possibility of applying the cationizing agent in the process of production of the viscose fibers, especially in the production of viscose silks. In these investigations the interaction of the cellulose and the cationizing agent is accomplished by the addition of the latter to the viscose solution. The changes of the technological parameters of several viscose solutions, containing different amounts of the cationizing product, have been followed. The possibility for the spinning of fibers from these solutions was also studied. The produced polyampholytic fibers have been characterized for their tensile strength, elongation and dyeing ability. [ABSTRACT FROM AUTHOR]

Multifunctional fibrous surfaces with ultraviolet protection, self-cleaning, or antibacterial activity have been highly attractive. Nanocomposites consisting of silver (AgNPs) and titanium dioxide (TiO2 NPs) nanoparticles (Ag/TiO2) were developed and coated onto the surface of viscose fibers employing a straightforward pad–dry–cure procedure. The morphologies and elemental compositions were evaluated by scan electron microscopy (SEM), infrared spectra (FTIR), and energy-dispersion X-ray spectra (EDS). The resultant multifunctional textile materials displayed antibacterial and photo-induced catalytic properties. The photocatalyzed self-cleaning properties were investigated employing the photochemical decay of methylthioninium chloride, whereas the antibacterial properties were studied versus E. coli. The viscose fibers coated with Ag/TiO2 nanocomposite demonstrated improved efficiency compared with viscose fibers coated with pure anatase TiO2 nano-scaled particles. [ABSTRACT FROM AUTHOR]

Exposure to different arsenic concentrations (higher than 10 μg/L), either due to the direct consumption of contaminated drinking water or indirectly by using contaminated food is harmful for human health. Therefore, it is important to remove arsenic from aqueous solutions. Among many arsenic removal technologies, adsorption offers a promising solution with a good efficiency, however the material used as adsorbent play a very vital role. The present investigation evaluated the behavior of two cellulose-based adsorbent materials, i.e., viscose fibers (V) and its TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) derivative, obtained by using the well-established TEMPO-mediated protocol (VF). Due to the known arsenic affinity for Fe ions the two materials were later doped with it. This was done after a preliminary functionalization with di-2-ethylhexyl phosphoric acid (DEHPA), to obtain two materials: V-DEHPA-Fe and VF-DEHPA-Fe. Arsenic adsorption is known to be pH dependent (between 6 and 8); therefore, the optimal pH range for As(V) adsorption has been established. In order to evaluate the adsorption mechanism for both the synthesized materials, the influence of contact time, temperature and initial concentration was evaluated. Langmuir, Freundlich and Sips equilibrium isotherm models were used in order to determine the ability of the model to describe As(V) adsorption process. The maximum adsorption capacity of the material V-DEHPA-Fe was 247.5 µg As(V)/g with an As(V) initial concentration of 5 mg/L and for the material VF-DEHPA-Fe it was 171.2 µg As(V)/g with initial concentration of 5 mg/L. [ABSTRACT FROM AUTHOR]