Preparation of regenerated cellulose fiber via carbonation (II)

Sodium cellulose carbonate (CC-Na) dissolved in 8.5 wt% NaOH/ZnO (100/2–3, w/w) aqueous solution was spun into some acidic coagulant systems. Diameter of regenerated cellulose fibers obtained was in the range of 15–50μm. Serrated or circular cross sectional views were obtained by controlling salt concentration or acidity in the acid/salt/water coagulant systems. Velocity ratio of take-up to spinning was controlled up to 4/1 with increasing spinning velocity from 5 to 40 m/min. Skin structure of was developed at lower acidity or higher concentration of coagulants. Fineness, tenacity and elongation of the regenerated cellulose fibers were in the range of 1.5–27 denier, 1.2–2.2 g/d, and 8–11.3%, respectively. All of CC-Na and cellulose fibers spun from CC-Na exhibited cellulose II crystalline structure. Crystallinity index was increased with increasing take-up speed.     

Novel fibers prepared from cellulose in NaOH/thiourea/urea aqueous solution

The regenerated cellulose fibers were prepared by wet-spinning from NaOH/thiourea/urea aqueous solvent system for the first time. The effects of coagulation and stretch conditions on the structure, morphology, and mechanical properties of the prepared fibers were investigated by wide-angle X-ray diffraction (WAXD), scanning electron microscope (SEM), and tensile tester, respectively. When the cellulose spinning dope was coagulated in 10% H₂SO₄/12.5% Na₂SO₄ aqueous solution at 15 °C, the prepared fibers had a typical crystalline structure of cellulose II and circular cross-sectional shapes with smooth surface and slightly high tensile properties to viscose fibers.     

Preparation and radiopaque properties of chitosan/BaSO4 composite fibers

Chitin and chitosan have been extensively investigated as a matrix of organic/inorganic composite. Barium, one of the radiopaque inorganic materials, can provide chitosan with radiopaque property by blending of chitosan and BaSO₄. The filtered and deaerated chitosan/BaCl₂ solutions were extruded into NaOH and Na₂SO₄ coagulation bath through a nozzle by gear pump. BaSO₄ was synthesized by the reaction between BaCl₂ and Na₂SO₄ in the coagulation bath, in which acidic chitosan solution was also solidified at the same time. In XRD, the introduction of BaSO₄ into chitosan fibers reduced the inherent peak of chitosan fibers. In angiographic observation, chitosan/BaSO₄ hybrid fibers exhibited the clear contrast images which become clear with an increase in BaSO₄ content.     

Gelation Modification of Alginate Nonwoven Fabrics

Calcium alginate nonwoven fabrics were gelation-modified by two-stage with aqueous HCl solution and then ethanolic NaOH solution. The structure and crystallinity properties of the samples were characterized by FT-IR, SEM, and XRD. The preparation conditions and modification mechanism were investigated. The results indicated that the crystal structure of calcium alginate fibers was destroyed; the crystallinity and calcium ion content decreased after HCl treatment. This resulted from the formation of ester bonds among the hydrolytic molecules after NaOH treatment. The best gel performance was obtained at the HCl concentration of 0.05-0.1 wt% with the NaOH concentration in ethanol of 2–4 mol/l. The liquid absorption of nonwoven alginate fabrics increased by 145 %. The water capability increased by 2673 % after modification, while the thickness, mass per unit area, permeability, and tensile strength of nonwoven alginate fabrics changed little.     

Study on optimum coagulation conditions of high molecular weight pan fiber in wet spinning by orthogonal experimental design

Orthogonal experimental design (I) and (II) were used to study optimum coagulation technology in wet spinning of high molecular weight PAN nascent fiber. Relationship between shape factor (De) and coagulation conditions such as coagulation bath concentration, temperature, and minus draw ratio was investigated to obtain nascent fiber with the minimum De value and smooth surface morphology. The nascent PAN fiber fabricated at the conditions of 80 wt% coagulation bath concentration (in this paper, the coagulation bath concentration refers to the mass concentration of DMSO in coagulation bath), 0 % minus draw ratio, and 40 °C coagulation bath temperature has the smallest fiber diameter, the most circular cross sectional (minimum shape factor) and smooth surface morphology, and the maximum density, which resulted in the most excellent mechanical properties of nascent PAN fiber.     

Preparation of regenerated cellulose fiber via carbonation. I. Carbonation and dissolution in an aqueous NaOH solution

Cellulose carbonate was prepared by the reaction of cellulose pulp and CO₂ with treatment reagents, such as aqueous ZnCl₂ (20–40 wt%) solution, acetone or ethyl acetate, at −5–0°C and 30–40 bar (CO₂) for 2 hr. Among the treatment reagents, ethyl acetate was the most effective. Cellulose carbonate was dissolved in 10% sodium hydroxide solution containing zinc oxide up to 3 wt% at −5–0°C. Intrinsic viscosities of raw cellulose and cellulose carbonate were measured with an Ubbelohde viscometer using 0.5 M cupriethylenediamine hydroxide (cuen) as a solvent at 20°C according to ASTM D1795 method. The molecular weight of cellulose was rarely changed by carbonation. Solubility of cellulose carbonate was tested by optical microscopic observation, UV absorbance and viscosity measurement. Phase diagram of cellulose carbonate was obtained by combining the results of solubility evaluation. Maximum concentration of cellulose carbonate for soluble zone was increased with increasing zinc oxide content. Cellulose carbonate solution in good soluble zone was transparent and showed the lowest absorbance and the highest viscosity. The cellulose carbonate and its solution were stable in refrigerator (−5°C and atmospheric pressure).     

Fabrication and characterization of nano Al<Subscript>2</Subscript>O<Subscript>3</Subscript> filled PVA:NH<Subscript>4</Subscript>SCN electrolyte nanofibers by electrospinning

Present paper reports a method of preparing polymer composite electrolyte nanofiber mat using polyvinyl alcohol (PVA), ammonium thiocynate (NH₄SCN) salt, and aluminium oxide (Al₂O₃) nano particles based on electrospinning technique. Two-stage process of preparation of nanofibers, namely, preparation of nano particles filled PVA electrolyte gel solution followed by its electrospinning has been used. The so obtained nanofibers have been characterized by XRD, DSC, SEM, and Conductivity measurements. XRD patterns affirm the formation of nanocomposite while SEM pictures reveal formation of fibers on a nano scale format (300–800 nm). Fibers of the electrolytes are seen to be thermally stable. Ionic conductivity of electrolyte fiber is seen to improve in the presence of nano filler at room temperature with a maximum at 5.31×10⁻³ Scm⁻¹ for 4 wt% filler concentration, which is comparable to that for corresponding dried gel electrolyte films.     

Effects of Ammonium Chloride Fertilizer and its Application Stage on Cadmium Concentrations in Wheat (Triticum aestivum L.) Grain

Abstract

Chloride (Cl) in saline soil increases the cadmium (Cd) concentration in crops. Here, we conducted a field experiment to investigate changes in Cd concentrations in wheat grain after the application of the Cl-containing fertilizer ammonium chloride (NH₄Cl), with the aim of reducing its potential health risk. Effects of the application stage of NH₄Cl fertilizer and leaching treatment (i.e., heavy rainfall) were also investigated in field and pot experiments. Both field and pot experiments showed that the Cd concentration of wheat grain was higher with NH₄Cl fertilizer than with ammonium sulfate or urea fertilizers. Grain Cd concentration in wheat fertilized with NH₄Cl at the tillering–jointing and flowering stages in the field experiment was 0.223 mg kg^–1, which was about 1.5 times higher than that fertilized with urea. This finding is important because, in Japan, compound fertilizers containing NH₄Cl are commonly used in fields for wheat cultivation. NH₄Cl fertilizer application at the tillering–jointing and flowering stages had nearly equal effects on the Cd concentration in wheat grain. Basal dressing with NH₄Cl fertilizer increased Cd concentrations in wheat grain to a greater extent than topdressing (at thetillering–jointing and flowering stage applications) in a pot experiment that was protected from rain. Leaching treatment (assuming two lots of 100 mm rainfall) negated the effect of NH₄Cl fertilizer application on Cd concentration in wheat grain. We recommend the use of ammonium sulfate or urea preferentially as the nitrogen fertilizer because heavy rainfall rarely occurs during this period in Japan.     

Coagulation studies for hydroxyethyl cellulose (HEC) in NaOH/H<Subscript>2</Subscript>O solvent

Hydroxyethyl cellulose (HEC)/NaOH frozen rods were applied in the investigation of the coagulation kinetics. The influence of coagulation variables such as types of coagulants, coagulation temperature, concentration of coagulant, and content of HEC on coagulation rate was intensively studied based on boundary movement theory. It was confirmed that the coagulation of HEC was actually diffusion-controlled process and sometimes accompanied with chemical reactions. The coagulation rate of HEC rods in strong acid (sulfuric acid) exceeded that in weak acid (acetic acid), while the coagulation rate in ethanol was the slowest. It was hard to determine the coagulation rate of HEC frozen rods in deionized water without pre-solidifying because of the difficulty in keeping the cylindrical shape of sample due to the low strength of the coagulated surface layer. Besides, the increase of acid concentration, temperature, or content of HEC would contribute to the improvement of coagulation rate. This study is important for understanding and controlling the shaping process of HEC.     

Modification of natural bamboo fibers for textile applications

Natural bamboo fibers have excellent properties suggesting that there is a good potential for them to be used in textiles; however, they have not received the attention that they deserve owing to their coarse and stiff quality. Therefore, a chemical method for extraction and modification of natural bamboo fibers for textile end uses were developed and optimized in this paper. The quality of natural bamboo fibers were characterized by their chemical composition, linear density, and tenacity. Experimental results show that the modified bamboo fibers are finer, with significant lower content of noncellulosic substances. The processing parameters are optimized as: 20 g/l NaOH, 3 g/l Na₅P₃O₁₀, 5 g/l Na₂SO₃, 3 g/l penetrating agent, with a fiber to liquid ratio of 1:10, at 100 °C for 2 h, and the bamboo fiber thus produced has cellulose amount of 73.25 %, fineness of 3.26 tex, average length of 44.5 mm, breaking elongation of 2.8 % and tenacity of 2.41 cN/dtex. The result of this study may offer a possibility of developing natural bamboo fibers into practical applications in textiles.     

The novel use of sodium borohydride as a protective agent for the chemical treatment of vegetable fibers

The vegetable fibers used as reinforcement for polymer matrix composites are usually treated to improve their adhesion with the matrix. The chemical treatment with sodium hydroxide (NaOH) is widely employed, but it may damage the fiber surface structure, reducing its strength. This novel study is related to the use of hydride ions (H^?) as protective agent for vegetable fibers, under alkaline treatment, as a way to promote their use in polymeric composites. Sisal fibers were modified by immersion in a NaOH aqueous solution (2, 5, and 10 % wt/vol) with or without the addition of sodium borohydride (NaBH₄) (1 % wt/vol) under different treatment conditions. The treated fibers were characterized via density and moisture content analyses and also using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The effectiveness of NaBH₄ to protect the sisal fiber was more pronounced in moderate NaOH concentrations (5 %) at room temperature or higher for shorter alkaline treatment times.     

Synthesis of non-water soluble polymeric guanidine derivatives and application in preparation of antimicrobial regenerated cellulose

In order to prepare antimicrobial regenerated cellulose fibers from blended spinning solutions, three non-water soluble polymeric guanidine derivatives, polyhexamethylene guanidine dodecyl benzene sulfonate (PHGDBS), polyhexamethylene guanidine dodecyl sulfate (PHGDSA), and polyhexamethylene guanidine laurylsulfonate (PHGLSO) were synthesized. And the chemical structure of these agents was verified by element analysis, Fourier transform infrared spectroscopy (FTIR), and proton nuclear magnetic resonance (¹H-NMR). The antimicrobial activity of the three agents as well as cellulose films containing PHGDBS was also studied. The results showed that the compounds we prepared had strong properties against both bacterial and fungus, including Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), Candida albicans, and Aspergillus niger. Moreover, it was found that three antimicrobial agents were insoluble in water but they can dissolve in solvents of cellulose such as 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) and N-methylmorpholine-N-oxide monohydrate (NMMO·H₂O). Meanwhile, it was also proved that [BMIM]Cl had little effect on the antimicrobial properties of these agents. The cellulose films containing only 1.0 wt% PHGDBS showed 99.94 % and 96.95 % bacterial reduction rates for S. aureus and E. coli, respectively. Moreover, still over 91 % of bacterial reduction was maintained after 15 laundering cycles. It suggests that the three agents will be suitable to prepare antimicrobial regenerated cellulose fibers or films.     

Fabrication of meta-aramid fibrid by precipitation

“Fibrid”, a type of fibrous particle used for binding, and the meta-aramid fibrids were successfully prepared by injecting the meta-aramid solution into the high shearing coagulation bath in this paper. The meta-aramid solution was prepared by dissolving the meta-aramid fibers in LiCl/DMAc solving system, and the mixture of water and DMAc was used as coagulation bath. The rotating speed, concentration of meta-aramid solution and the concentration of water in the coagulation bath were the main factors on effecting the formation and morphology of fibrids. The results showed that the length of meta-aramid fibrid decreased with the rotating speed and the content of water in coagulation bath increasing, and increased with the concentration of meta-aramid solution increasing. The morphology of meta-aramid fibrid were observed by optical microscope, a lower thermal property of meta-aramid firbid than meta-aramid fiber was observed in TGA which was mainly due to the breaking of hydrogen bonding and crystalline structure of meta-aramid fiber during the dissolving process, the results in TGA were consistent with the XRD, and the XRD curves showed that the non-crystalline structure were observed in meta-aramid fibrid.     

Fractional isolation and partial characterization of non-starch polysaccharides and lignin from sago pith

Sago pith non-starch polysaccharides were fractionated into cold water solubles (2.6%), hot water solubles (0.8%), dimethylsulfoxide solubles (0.8%), 5% NaOH soluble hemicelluloses (1.2%), 24% KOH–2% H₃BO₃ soluble hemicelluloses (0.6%), and cellulose (5.3%). Lignin was measured by 5% NaOH extraction (0.6%) and sodium chlorite oxidation (4.2%). Glucose and rhamnose were the major sugars in cold and hot water soluble non-starch polysaccharides. The neutral sugars in dimethylsulfoxide (DMSO) soluble non-starch polysaccharides were found to be enriched in rhamnose, xylose, glucose, and arabinose. Extraction of sago pith with aqueous 5% NaOH produced hemicelluloses, which were enriched in xylose and, to a lesser extent, glucose, arabinose, galactose, and rhamnose-containing polysaccharides, together with 7.4% uronic acids and 3.9% lignin. Further extraction of the delignified pith residue with aqueous 24% KOH and 2% H₃BO₃ removed the residual hemicellulosic fraction, which was enriched in glucose and xylose-containing polysaccharides, together with 5.8% uronic acids and 1.1% associated residual lignin. Six phenolic acids and aldehydes were detected in the mixtures of alkaline nitrobenzene oxidation of 5% NaOH soluble lignin and associated lignin in hemicelluloses and cellulose fractions. The lignin fraction contained a high proportion of non-condensed syringyl units and small amounts of non-condensed guaiacyl units as well as fewer non-condensed p-hydroxyphenyl units.     

Removal of benzidine-based azo dye from aqueous solution using amide and amine-functionalized poly(ethylene terephthalate) fibers

In this study, amide and amine groups bound to poly(ethylene terephthalate) fibers are used to remove the colored toxic Congo red dye from aqueous solution. The effects of process variables like pH, contact time, graft yield, and initial dye concentration on the adsorption were investigated. The maximum adsorption of Congo red to amide and amine groups was observed at pH 3 and 5 respectively. Equilibrium was attained at approximately 60 min for the amine group. The adsorption capacity of amine group on the poly(ethylene terephthalate) fiber was 46.5 mg g⁻¹ at 25 °C, which was higher than that of the amide group on the poly(ethylene terephthalate) fiber. Desorption was done using 0.1 M NH₃, and recovery was measured at 58.2 %. The used adsorbent was regenerated and recycled six times. The results showed that the amine-functionalized fiber could be considered as potential adsorbents for removal of Congo red from aqueous solution.     

Dissolution of cellulose in NaOH based solvents at low temperature

Three low-cost types of complex solvents systems were carried out to dissolve cellulose, which were NaOH/urea/acetamide, NaOH/urea/tetraethyl ammonium chloride, and NaOH/acetamide/tetraethyl ammonium chloride. As an effective dissolution, NaOH/acetamide/tetraethyl ammonium chloride behaved as the optimum system, and the solubility was 89 % under the conditions of: NaOH 8 wt%, acetamide 10 wt%, tetraethyl ammonium chloride 6 wt%, distilled water 76 wt%, and freezing temperature ?5°C. With the analysis of Ubbelohde viscometer, infrared spectra (FTIR), wide-angle X-ray diffraction (XRD), and thermogravimetric analysis (TGA) for the original and regenerated cellulose samples, it was indicated that the viscosity-average molecular weight had no significant changes in the dissolution process, the crystalline structure of cellulose was converted to cellulose II from cellulose I in native cellulose, and the regenerated cellulose had a good thermal stability.     

Preparation and characterization of cellulose nanofiltration membrane through hydrolysis followed by carboxymethylation

Bamboo cellulose (BC) is hydrophilic, biodegradable and inexhaustible. The bamboo cellulose membrane (BCM) is one of the best materials to replace petroleum-based polymer film for water purification. In this study, the N-methylmorpholine-N-oxide (NMMO) was used as a solvent to dissolve cellulose 6 wt.%, and regenerated cellulose membrane was prepared by phase inversion. A new kind of cellulose nanofiltration membrane (BC-NFM) was obtained by the hydrolysis and carboxymethylation of dense cellulose membrane (BCM). The modification was carried out through hydrolysis followed by carboxymethylation. The BC-NFM was characterized by XRD, FT-IR, SEM and thermal analysis. BC-NFM performance evaluation instrument were used to evaluate retention rate and water flux of nanofiltration membrane. BCM was immersed in 1 mol/l NaOH and 3 wt/v.% chloroacetic acid solution to obtain BC-NFM. By calculating, pore size of nanofiltration membrane was 0.63 nm. With a pressure of 0.5 MPa, the water flux of nanofiltration membrane for Na₂SO₄ solution was 10.32 l/m²h, and the retention rate was 68.4 %. The water flux for NaCl solution was 13.12 l/m²h, and the retention rate was 34.9 %. And the retention rates were 93.0 % and 98.9 % for methyl orange and methyl blue, respectively. The stability of the nanofiltration membrane was measured by the thermal analyzer, following the order of BC>BCM>BC-NFM. The prepared cellulose nanofiltration membrane exhibited good stability in water treatment process, and can be used to remove organic compounds in aqueous solutions.     

Graft copolymerization of granular allyl starch with carboxyl-containing vinyl monomers for enhancing grafting efficiency

Graft copolymerization of granular allyl starch with carboxyl-containing vinyl monomers using H₂O₂/Fe²⁺ initiator in aqueous dispersion was investigated for enhancing grafting efficiency of the copolymerization. The graft copolymerization was evaluated in terms of grafting efficiency, grafting ratio, and conversion of monomer to polymer. Influences of both allyl etherification of starch and structures of vinyl monomers used on the copolymerization were revealed. Variables such as molar ratio of Fe²⁺ to H₂O₂, initiator concentration, monomer concentration, polymerization temperature, and time of the graft copolymerization were also studied. It was found that allyl etherification of starch enhanced the grafting efficiency and grafting ratio evidently. Acrylic acid exhibited the greatest grafting efficiency and ratio for the copolymerization after starch was allyl-etherified. The copolymerization should be carried out under the protection of nitrogen gas at 30–35 °C for 3 h by using H₂O₂/Fe(NH₄)₂(SO₄)₂ as initiator. Preferred molar ratio of H₂O₂/Fe(NH₄)₂(SO₄)₂/anhydroglucose was in a range of 20/1/1000 to 60/3/2000.     

Dissolving lignocellulosic biomass in a 1-butyl-3-methylimidazolium chloride-water mixture

An ionic liquid (IL)-water mixture employed to treat lignocellulosic biomass is promising. The addition of water decreases viscosity and process cost so as to improve the IL practical application. In this work, effects of temperature (50-170 °C), water content (0-80 wt%), treating duration (0.5-4 h) and pressure (0.1-3.2 MPa) on treating legume straw process using a 1-butyl-3-methylimidazolium chloride ([C₄mim]Cl)-water mixture were experimentally investigated. Legume straw was found to be partially dissolved, and the dissolved substances can be flocculated by adding the coagulating agent—water (equal to volume of the solution). For this process at 0.1 MPa, the maximum 29.1 wt% legume straw is dissolved in the [C₄mim]Cl-water mixture with water content of 20 wt% at 150 °C during 2 h, which is much higher than 9.8 wt% using pure [C₄mim]Cl. A hemicellulose-free lignin-rich material (64.0 wt% lignin and 35.3 wt% cellulose) is obtained by adding the water. Even for 0.5 h, 22.3 wt% of legume straw is dissolved in the case of water content of 20 wt%, 150 °C and 0.1 MPa. High pressure favors the dissolution of legume straw but lignin content in the residue has no obvious change. The addition of proper amount of water facilitates the dissolution of legume straw and a relative rapid dissolving rate can be achieved in a [C₄mim]Cl-water mixture. There are great differences in chemical and physical properties between legume straw and the obtained samples (residue and floc) due to the dissolution and reconstitution.     

Rheological behavior and spinnability of ethylamine hydroxyethyl chitosan/cellulose co-solution in N-methylmorpholine-N-oxide system

In this work, the novel chitosan derivative ethylamine hydroxyethyl chitosan (EHC) was synthesized and blended with cellulose in an aqueous N-methylmorpholine-N-oxide (NMMO) solution in order to fabricate antibacterial chitosan/cellulose fiber. The rheological behaviors of the obtained co-solution in both steady and dynamic states were carefully investigated to determine the spinnability of the co-solution. In steady state, the addition of EHC was found to preserve the power-law flow characteristics of cellulose in the aqueous NMMO solution, while broadening the first Newtonian fluid-flow area. Under dynamic conditions, both Han-plot and viscoelastic analyses indicated the homogeneity of the co-solution. EHC/cellulose antibacterial fibers were successfully spun via the lyocell process using aqueous NMMO as the solvent, confirming the excellent spinnability of the EHC/cellulose co-solution. Scanning electron microscopy was used to observe the morphology of the obtained EHC/cellulose fibers; they were also investigated for antibacterial activity. The obtained EHC/cellulose fiber exhibited good spinning consistency and strong antibacterial activity against Escherichia coli, demonstrating potential applications for the material in antibacterial textiles.