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.     

Performances of ramie fiber pretreated with dicationic imidazolium ionic liquid

The chemical structure of a new gemini dicationic imidazolium ionic liquid, 3,3′-[1,2-ethanediylbis (oxy-2,1-ethanediyl)]-bis[1-methyl-imidazolium]-dibromide (PEG₁₅₀-DIL) was established by ¹H-NMR and elemental analyses. Then, PEG₁₅₀-DIL was applied to pretreat ramie fiber. PEG₁₅₀-DIL treated ramie fiber was characterized by FT-IR, XRD, DSC-TG and FE-SEM. Finally, the mechanical and dyeing properties of PEG₁₅₀-DIL pretreated ramie fibers were studied. The optimum condition of PEG₁₅₀-DIL modification was carried out at 100 °C for 30 min. The color strength increased obviously with the duration time and temperature of the PEG₁₅₀-DIL. The tensile strength and strength retention of PEG₁₅₀-DIL -treated ramie fibers decreased with the increase of pretreating time and temperature. The tensile strength retention was 86.20 % under optimal PEG₁₅₀-DIL pretreating condition (100 °C, 30 min).     

Influence of residual ionic liquid on the thermal stability and electromechanical behavior of cellulose regenerated from 1-ethyl-3-methylimidazolium acetate

The regenerated cellulose films were prepared by dissolving cotton cellulose pulp directly in room temperature ionic liquid namely, 1-ethyl-3-methylimidazolium acetate at 80 °C, followed by washing/curing in different coagulants namely, methanol, deionized water, methanol-deionized water, and isopropyl alcohol-deionized water. It was found that the type of coagulants employed for curing the cellulose films has a significant influence on the amount of residual ionic liquid entrapped in the films. The amount of residual ionic liquids was 2.68, 1.01, 0.84, and 0.75 wt.% for the films cured with deionized water, isopropyl alcohol-deionized water, methanol, and methanol-deionized water, respectively. The DTG peaks of regenerated cellulose films showed two decomposition temperatures at 280 °C and 320 °C. Among all the cases studied, deionized water curing case showed the lowest decomposition temperature, attributed to entrapment of large residual ionic liquid in it. Electromechanical characteristic of the regenerated cellulose films was also investigated.     

Effect of degree of polymerization on the mechanical properties of regenerated cellulose fibers using synthesized 1-allyl-3-methylimidazolium chloride

1-Ally-3-methylimidazolium chloride ([AMIM]Cl) was successfully synthesized and was used as a green spinning solvent for cellulose. The celluloses of various degrees of polymerization (DP) were dissolved in the [AMIM]Cl to obtain 5 % (w/w) cellulose solutions, which were regenerated to cellulose fibers through wet spinning process. Of three different regenerated cellulose fibers with different DPs, a DP of 2,730 was gave the strongest regenerated fiber without drawing having a tensile strength of 177 MPa and an elongation at break of 9.6 % respectively, indicating that celluloses of higher molecular weight can be entangled and oriented more easily. Also maximum draw ratio of the as-spun fibers increased from 1.2 to 1.7 with increasing degree of polymerization leading to a tensile strength and modulus of 207 MPa and 48 GPa, respectively. Particularly the tensile modulus was substantially higher than those of lyocell and high performance viscose fibers of 20 GPa or less. The higher DP of pristine cellulose was critical in increasing the mechanical properties such as tensile strength and elongation at break of the as-spun fibers coupled with higher tensile modulus after drawing.     

Properties of flame-retardant cellulose fibers with ionic liquid

Flame-retardant cellulose fibers were prepared by dissolving cellulose in tetrabutylammonium acetate and dimethyl sulfoxide, and blending with amino silicone oil (ASO). The ASO was used as a novel fabric softener and flame retardant for cellulose fibers. Fourier-transform infrared spectroscopy showed that blending with ASO did not adversely affect the cellulose fibers. The flame retardancy of the cellulose fibers blended with ASO was determined based on the limiting oxygen index (LOI). Cellulose fibers blended with 8 wt% (add-on) ASO gave the best flame retardancy, with an LOI of 28, which was higher than that of the virgin fibers. The thermal properties of the flame-retardant cellulose fibers were investigated using differential scanning calorimetry and thermogravimetric analysis. The results showed that ASO prevented degradation of the cellulose fibers, hindered the formation of volatile species, and favored char formation. The mechanical properties of the flame-retardant cellulose fibers were better than those of virgin cellulose fibers.     

Isolation of cellulose with ionic liquid from steam exploded rice straw

Isolation of cellulose from straw is a bottleneck for exploiting such biomass resources. In recent years, considerable concerns have arisen over new efficient and environmentally friendly way for this purpose. A novel method for cellulose isolation has been proposed by dissolving steam exploded rice straw in 1-allyl-3-methylimidazolium chloride ionic liquid (IL), following regeneration of crude cellulose by diluting the cellulose-ionic liquid solution adequately after separation of insoluble residues. The crude cellulose was then bleached by 2% hydrogen peroxide aqueous solution with low-flux ozone blowing into. No acid-insoluble lignin and only 0.85% hemicelluloses were detected in the bleached cellulose. The isolated cellulose was analyzed by SEM, FT-IR, ¹³C CP/MAS solid state NMR, XRD spectroscopes, and the results indicated that high quality cellulose preparation could be isolated in this manner from rice straw.     

Property of ramie fiber degummed with Fenton reagent

This paper investigated the performance and morphology of ramie fibers degummed using Fenton reagent. In order to deeply understand the reaction characteristics, SEM, XRD and FT-IR were employed to characterize the morphologies, chemical components and crystallinity of degummed fibers. Also, the physical and mechanical properties such as tenacity, breaking elongation, density, softness and degree of polymerization of degummed fibers were measured. The experimental results indicated that Fenton can serve as an effective oxidation degumming agent under weak acid condition. The new degumming method could remove more gummy components from raw ramie, whereas the cellulose content in treated fibers was further increased compared with the alkaline oxidation degumming. The fibers degummed using Fenton showed slight increase in tenacity and significant increase in density as well as breaking elongation comparing with alkaline oxidation degumming. The degummed fibers were also characterized in terms of SEM, XRD and FTIR which confirmed the effectiveness of the new degumming method.     

Functionalizing cellulose scaffold prepared by ionic liquid with bovine serum albumin for biomedical application

The present study reports the preparation of a cellulose scaffold for tissue engineering directly from cellulose fiber using ionic liquid (IL) by the NaCl leaching method with bovine serum albumin (BSA), which is well known protein utilized for biomedical applications like degradation of polymer, cell attachment and proliferation on scaffold. The 1-n-allyl-3-methylimidazolium chloride (AmimCl) IL was used as a solvent for cellulose. The morphology of the scaffold was studied by scanning electron microscopy (SEM) and the images showed that the pore sizes of the scaffolds were about 200 µm. In addition, the water uptake (WU) and degree of degradation of the cellulose scaffold were measured. Meanwhile, the biocompatibility and bioactivity of the scaffold were determined via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenytetrazolium bromide (MTT) assay and the Live/Dead viability test. The various results demonstrated the ability of the Mesenchymal stem cells (MSC) to attach to the surface of the scaffolds amplified as percentage of BSA increased in cellulose scaffold.     

Air-gap spinning of cellulose/ionic liquid solution and its characterization

In order to study the effects of the spinning conditions on the structure and the properties of the regenerated fiber, cellulose was dissolved in ionic liquid and then spun into fiber using an air-gap spinning process. The solution concentration, the take-up speed and the fixation of the fiber ends during coagulation improved the crystallinity and the tensile strength at the same time. The fiber surface became smooth by addition of DMF (dimethylformamide). However, it decreased the crystallinity and the tensile strength of the fibers. We revealed that the developed structure during coagulation determined the morphology and the properties of the fibers. The co-solvent resulted in smooth surface of the fiber and also changed the mechanical properties.     

Preparation of chitosan fibers using aqueous ionic liquid as the solvent

In this work, acidic ionic liquid glycine hydrochloride (Gly·HCl) is reported as a new solvent for dissolving chitosan. The regenerated chitosan fibers were fabricated by a wet spinning process and characterized by scanning electronic microscopy, fourier transform infrared spectroscopy, wide-angle X-ray diffraction and thermal gravimetric analysis. The result shows that the regenerated chitosan fibers had the same chemical structure as the raw chitosan flake, however, its thermal stability and crystallinity is a little low. Furthermore, a new mechanism of dissolving chitosan in ionic liquid was proposed. The chitosan fibers had soft feeling, excellent antibacterial property and have huge potential application in biomaterials.     

Homogeneous lauroylation of ball-milled bamboo in ionic liquid for bio-based composites production: Part I: Modification and characterization

Ball-milled bamboo meal was completely dissolved under constant conditions (130 °C, 6 h) in the ionic liquid ([C₄mim]Cl) and then the lauroylation was carried out at different conditions. The various factors, such as molar ratio and temperature, were investigated to evaluate the effect of modification. Results showed that the molar ratio played a very important role for the lauroylation. The weight percent gain (WPG) ranged from 167% to 528% when the molar ratio increased from 1.0 to 2.0 for 2 h. It has been shown that the highly substituted bamboo derivatives could be obtained by reacting bamboo meal with lauroyl chloride as the molar ratio is 2.0. All reactions were performed under mild conditions, low excess of reagent and a short reaction time as compared to the heterogeneous chemical modification. The physicochemical properties of the bamboo derivatives were also widely investigated. Results obtained from FTIR and NMR spectroscopies confirmed that the lauroylated derivatives were successfully synthesized in one step. It was also found that thermal stability of the esterified derivatives is lower than that of the unmodified bamboo meal. Moreover, the morphological properties of the esterified bamboo meal were significantly changed by chemical modification. The rough appearance of bamboo meal changed into a relatively homogeneous and smooth surface morphology after lauroylation. Furthermore, the lauroylated bamboo meal had excellent solubility in chloroform, which provides feasibility to electrostatic spinning of modified bamboo meal as biomaterials for industries.     

High-intensity ultrasound irradiated modification of sugarcane bagasse cellulose in an ionic liquid

This current work is concerned with the glutarylation of sugarcane bagasse cellulose in ionic liquid 1-butyl-3-methylimidazolium chloride by ultrasound irradiation without catalyst. The degree of substitution ranging from 0.22 to 1.20 was obtained in one-step homogeneous modification, which increased with ultrasound irradiation time, temperature, and the molar ratio of glutaric anhydride/anhydroglucose unit in cellulose. The structural characterization of the glutarylated cellulose was carried out by using FT-IR and CP/MAS ¹³C NMR and the results showed that the glutarylation reaction occurred. The thermal stability of the glutarylated cellulose decreased upon chemical modification.     

苎麻杂交一代性状分离变异研究

三个组合苎麻杂交一代性状分离变异如下：（１）形态学性状分离复杂、类型繁多，如（黄壳早×芦竹青）Ｆ１６８个单蔸可分为６３个类型。（２）经济性状变异显著，如株高和单蔸分株数的变异系数为１０．２—１９．７％和４１．０—４１．７％，各组合后代不同类型间单纤维支数的差异为５００—１０００支，变异系数为１０．４－１５．５％。（３）有些组合Ｆ１的叶面绉纹少：多、幼茎绿色：黄绿、叶形卵圆：椭圆等符合１：１的分离比例，而叶缘锯齿深尖：浅钝、托叶红色：黄白等分离比例适合９：７。     

Antibacterial blend films of cellulose and chitosan prepared from binary ionic liquid system

A new hybrid ionic liquids solvent, 1-allyl-3-methylimidazolium chloride (AMIMCl) and glycine hydrochloride (Gly·HCl) was utilized to dissolve chitosan and fabricate chitosan/cellulose (Cs/Ce) blend films with chitosan proportion varying from 2 to 35 wt.% through solution casting method. FTIR, XRD, TG, SEM and EA were used to evaluate the prepared composites. Besides, the mechanical property and antibacterial activity were also analyzed. The shifting of the characteristic peaks of -NH and C=O for chitosan, similar crystal pattern with low intensity diffraction peaks at 2θ of around 20°, superior thermal stability (increased T_onset) with chitosan ratio below 10 wt.% in the composites suggested that the interactions via hydrogen bonds formed between chitosan and cellulose. Besides, the elemental analysis showed that the actual N% contents from the chitosan in the blend films were roughly equivalent to the theoretical value though the inevitable residue of ionic liquids. Furthermore, the blends not only presented compact structure but also processed high bacterial reduction to E. coli and S. aureus at pH 6.3, which indicated that the Cs/Ce blend films prepared via the Gly·HCl/AMIMCl dissolution method were suitable for production of degradable antibacterial materials.     

Dissolution and regeneration behavior of chitosan in 3-methyl-1-(ethylacetyl)imidazolium chloride

3-methyl-1-(ethylacetyl)imidazolium chloride ([EtMIM]Cl), was synthesized for chitosan dissolution, and the dissolution and regeneration behaviors of chitosan in [EtMIM]Cl were thoroughly investigated. The solubility of chitosan in [EtMIM]Cl was measured at temperatures ranging from 40 °C to 110 °C, based on which the thermodynamic parameters of chitosan in [EtMIM]Cl were calculated. The polarizability and hydrogen bond accepting ability was determined by solvatochromic UV/vis spectroscopy. The regenerated chitosan from [EtMIM]Cl by adding methanol was characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Density functional theory (DFT) computations were performed to study the interactions between [EtMIM]Cl and chitobiose. Five kinds of hydrogen bonds, C-H/O, O-H/O, O-H/Cl, C-H/Cl, N-H/Cl were found, suggesting strong interactions between [EtMIM]Cl and chitobiose. In particular, the oxygen atom and the active methylene group of carboxylic ester in [EtMIM]⁺, formed strong hydrogen bonding with chitobiose. The molecular simulation results indicated that both the Cl^? anions and [EtMIM]⁺ cation played important roles in the chitosan dissolution process, by the disruption of native hydrogen bonds of chitosan.     

Hydrolysis of polycarbonate using ionic liquid [Bmim][Cl] as solvent and catalyst

The hydrolysis of polycarbonate (PC) was studied using ionic liquid [Bmim][Cl] as solvent and catalyst. The effects of reaction temperature, water dosage and [Bmim][Cl] dosage on reaction results were examined. It was showed that the hydrolysis conversion of PC was almost 100 % and the yield of bisphenol A (BPA) was over 95 % under the reaction conditions of temperature 165 °C, time 3.0 h, m([Bmim][Cl]):m(PC)=1.5:1 and n(H₂O):n(PC)=10:1. The ionic liquid could be reused for 8 times without obvious decrease in the conversion of PC and yield of BPA. Therefore, an environmental friendly strategy for chemical recycling of PC was developed.     

A comparison study on phase transition and structure of cornstarch in dimethyl sulfoxide and ionic liquid systems

A comparison study of the phase transition and structure of waxy cornstarch in DMSO and AMIMCl systems was conducted using a differential scanning calorimeter, an optical microscope, a scanning electron microscope, X-ray diffraction and thermogravimetric analysis. A full disruption and dissolution of starch granules was completed in 10 h at room temperature in pure DMSO, which was faster and more effective than that in ionic liquid 1-allyl-3-methylimidazolium chloride (AMIMCl). When dispersed in DMSO/water and AMIMCl/water at various ratios, respectively, different phase transitions were clearly exhibited, and the appearance and crystal structure of starch granules were significantly damaged with an increase in the concentration. Basing on the study of the decomposition temperature change through TGA measurements, a decreased temperature was observed in both DMSO and AMIMCl system, meaning starch degradation occurred with different levels. The huge temperature change from 357 to 328 °C were found in AMIMCl system, which most likely induced the distinct exothermic phenomenon in the DSC observation due to a significant depolymerization of starch.     

1-Aminoanthraquinone Diazonium Salt on the Coupling Modification Dyeing of Silk Fibroin with Enhanced Color Fastness

Chromophore incorporated into the protein chains through residue modification on silk fibroin will be an important way to get new dyeing technology with improved color fastness. Herein, 1-aminoanthraquinone diazonium salt was prepared and used for the modified dyeing on tyrosine of silk fibroin. The silk after modified dyeing was measured by UV-Vis, FTIR, MS, ¹H-NMR, Data color, and other testing techniques. Interestingly, the resulting silk showed excellent rub and wash fastness. The enhanced color fastness is contributed by an electrophilic substitution reaction between 1- aminoanthraquinone diazonium salt and the ortho position of phenolic hydroxyl in tyrosine molecular. Moreover, the mechanical property of silk was protected effectively by the mild coupling modified dyeing, better than the traditional acid dyeing under high temperature for a long time. This facile strategy provides an alternative approach to silk dyeing and benefits the silk applications.     

Modification of polyacrylonitrile precursor fiber with hydrogen peroxide

Polyacrylonitrile (PAN) precursor fibers were modified for different periods of time using hydrogen peroxide aqueous solution. A variety of tests were employed to characterize the fibers. The modification could induce cyclization and oxidation in the precursor fibers, as reflected by the changes in length and diameter of the fibers, and the results of Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Compared with the unmodified fiber, the modified fibers released less heat during a heating process similar to stabilization of PAN precursor fiber. Also, the modified fibers showed lower characteristic temperatures on differential scanning calorimetry (DSC) thermograms, and lower onset temperature of weight loss on thermal gravimetry (TG) curves. The modified fibers had more surface defects and hence exhibited lower tenacity and tensile modulus. Compared with the unmodified fibers, however, the modified fibers had smoother surface and fewer defects after stabilization. The strain decreased with increasing temperature under a constant tension for all the fibers. At the temperatures above 200 °C, the shrinkage of the fibers decreased with the increase of modification time, because a certain degree of cyclization and oxidation occurred in modified fibers, making them shrink less in the temperature range equivalent to stabilization.     

MUF树脂浸注改性橡胶木初步研究

采用水溶性三聚氰胺-尿素-甲醛(MUF)共聚树脂浸注处理人工林橡胶树(Hevea brasiliensis)木材,分析树脂浓度对各项物理力学性能指标的影响。结果表明：MUF树脂对橡胶木有良好的浸注性,随着浸注树脂浓度的升高,木材的增重率逐渐增加4.51%～31.73%;气干密度明显提高3.57%～25.62%;明度指数下降7.39%～11.85%;吸湿率下降12.81%～23.68%,吸水率降低12.73%～29.51%,尺寸稳定性明显改善;抗弯弹性模量增加1.01%～18.15%,抗弯强度提高3.38%