A new process for dissolution of cellulose in ionic liquids

A new dissolving process (two‐step dissolving process), that is, cellulose was first swelled to the maximum in aqueous 1‐butyl‐3‐methylimidazolium chloride ([BMIM]Cl) solution, and then dissolved by stirring under vacuum to remove excessive water, was developed to prepare the cellulose/[BMIM]Cl spinning dope with high quality. The results showed that the initial water contents in [BMIM]Cl have great influence on the swelling and dissolution of cellulose, and the suitable swelling range of aqueous [BMIM]Cl solution, in which cellulose can be swollen but not dissolved, was 2–5% water content. In this range, the higher water content in aqueous [BMIM]Cl solution, the more swelling time would be taken for cellulose to reach the maximal swelling ratio. Based on these results, cellulose/[BMIM]Cl spinning dopes were prepared by using two‐step dissolving process. In the range of our experiments, cellulose spinning dopes prepared by the two‐step dissolving process had better properties, such as fewer particles, lower apparent viscosity, and higher uniformity, compared with the direct dissolving process. By using this new dissolving process, the spinning performance of cellulose/[BMIM]Cl dopes was improved, and the mechanical properties of regenerated cellulose fibers were better than those prepared by the direct dissolving process. Therefore, it is a good way to prepare cellulose/[BMIM]Cl spinning dopes by using the new dissolving process. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

纤维素原料/离子液体溶液体系流变性能的研究

利用NDJ-1型旋转粘度计分别对木浆/离子液体氯化1-丁基-3-甲基咪唑([BMIM]Cl)溶液体系和水洗汽爆麦草/[BMIM]Cl溶液体系的流变性能进行了研究。考察了转子转速、温度、纤维素浓度及添加剂等对溶液粘度的影响。结果表明,两种溶液体系的流动活化能均较低,分别为42 kJ/mol和47 kJ/mol,其表观粘度随温度升高而降低;纤维素浓度和浆粕聚合度的增加都可使溶液的粘度增加。进一步研究了不同添加剂对粘度的影响,发现二甲基亚砜(DMSO)、N,N-二甲基乙酰胺(DMAC)和1,4-二氧六环的加入都能降低溶液的粘度,但以DMSO的效果最佳。     

浆粕性质对纤维素/[Bmim]Cl纺丝原液性能的影响

选用棉浆和木浆3种纤维素浆粕为原料,以离子液体1-丁基-3-甲基咪唑氯盐([Bmim] Cl)为溶剂,探讨了浆粕的聚合度(DP)和α-纤维素含量对其在[Bmim] Cl中的溶解情况、纺丝液的流变行为及其纤维性能的影响.结果表明:浆粕的DP和α-纤维素含量越高,其在[Bmim] Cl中完全溶解所需时间就越长;相对于α-纤...     

Fabrication of cellulose membrane with “imprinted morphology” and low crystallinity from spherulitic [Bmim]Cl

In the present study, regenerated cellulose membrane with “imprinted morphology” and low crystallinity was fabricated from the crystal cellulose/[Bmim]Cl solution. Spherulites of 1‐butyl‐3‐methilimidazolium chloride ([Bmim]Cl) and cellulose/[Bmim]Cl solution were observed using polarized optical microscopy under certain condition. The fabricated cellulose membranes presented some particular characteristics compared with the membrane prepared from traditional cellulose/[Bmim]Cl solution. All the fabricated membranes were characterized by optical microscope, Wide‐angle X‐ray diffraction (WAXD), thermo‐gravimetric analysis, and mechanical testing. The images showed that the resulting membranes prepared from crystal cellulose/[Bmim]Cl solution were “imprinted” with patterns which originated from the crystalline structure of [Bmim]Cl. The results of WAXD showed that the obtained cellulose membrane exhibited low diffraction peaks and crystallinity of approximately 24.57%. Furthermore, the low crystallinity led to the low mechanical property (27.5 MPa), thermal stability (315.4 °C), and high moisture regain (9.5%). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43798.     

High‐strength regenerated cellulose fibers spun from 1‐butyl‐3‐methylimidazolium chloride solutions

High‐performance regenerated cellulose fibers were prepared from cellulose/1‐butyl‐3‐methylimidazolium chloride (BMIMCl) solutions via dry‐jet wet spinning. The spinnability of the solution was initially evaluated using the maximum winding speed of the solution spinning line under various ambient temperatures and relative humidities in the air gap. The subsequent spinning trials were conducted under various air gap conditions in a water coagulation bath. It was found that low temperature and low relative humidity in the air gap were important to obtain fibers with high tensile strength at a high draw ratio. From a 10 wt % cellulose/BMIMCl solution, regenerated fibers with tensile strength up to 886 MPa were prepared below 22 °C and relative humidity of 50%. High strengthening was also strongly linked with the fixation effect on fibers during washing and drying processes. Furthermore, an effective attempt to prepare higher performance fibers was conducted from a higher polymer concentration solution using a high molecular weight dissolving pulp. Eventually, fibers with a tensile strength of ～1 GPa and Young's modulus over 35 GPa were prepared. These tensile properties were ranked at the highest level for regenerated cellulose fibers prepared by an ionic liquid–based process. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45551.     

离子液体[BMIM]Cl处理汽爆活化玉米秸秆及酶解

为了提高玉米秸秆酶解还原糖产率,利用蒸汽爆破法活化玉米秸秆原料,并利用离子液体[BMIM]Cl进行处理,考察了汽爆压力和维压时间对处理后物料酶解还原糖产率的影响。结果表明,汽爆压力2.6 MPa,维压时间90 s下汽爆活化秸秆原料,[BMIM]Cl处理后,酶解24 h后还原糖产率较汽爆活化后物料提高了84.03%,较原料提高了286.83%。秸秆化学组分分析表明,[BMIM]Cl处理后物料纤维素质量分数增加了64.86%,X射线衍射(XRD)与扫描电镜(SEM)分析表明,其晶形结构转变为无定形结构,更有利于纤维素酶与底物作用。说明汽爆活化[BMIM]Cl处理能显著提高玉米秸秆的酶解还原糖产率。     

Effects of plasticization conditions on the structures and properties of cellulose packaging films from ionic liquid [BMIM]Cl

By using natural softwood pulp with higher degree of polymerization (DP = 1460) as cellulose source, 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) ionic liquid as solvent and glycerol as plasticizer, a novel cellulose packaging film was prepared. The effects of plasticization conditions on the structures, mechanical properties, permeability for oxygen and water vapor were measured by Wide-angle X-ray scattering, thermogravimetric analysis, scanning electron microscopy (SEM), and other techniques. The investigations suggested that the glycerol concentration and plasticizing time had great effect on the properties of the regenerated cellulose films. The crystal transformation of cellulose I to cellulose II occurred during the dissolution and regeneration process, combining with the decrease of thermal stability. The tensile strength decreased rapidly with the addition of glycerol and prolongation of plasticizing time. However, elongation at break of the regenerated cellulose films increased at first and then decreased with increasing of glycerol concentration and plasticizing time. The morphologies for the fracture surface obtained from SEM images showed transformation of typical brittle fracture to plastic deformation with increasing of glycerol concentrations. It was also found that both water vapor permeability and oxygen permeability of the regenerated cellulose films decreased slowly with increasing of glycerol concentrations and plasticizing time, but water vapor permeability and oxygen permeability presented an almost opposite trend. The films prepared by using ionic liquid technology would be used in food packaging or other fields as a kind of green packaging material. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Rheological characterization of concentrated cellulose solutions in 1‐allyl‐3‐methylimidazolium chloride

The rheological properties of high concentrated wood pulp cellulose 1‐allyl‐3‐methy‐limidazolium Chloride ([Amim]Cl) solutions were investigated by using steady shear and dynamic viscoelastic measurement in a large range of concentrations (10–25 wt %). The measurement reveals that cellulose may slightly degrade at 110°C in [Amim]Cl and the Cox–Merz rule is valid for 10 wt % cellulose solution. All of the cellulose solutions showed a shear thinning behavior over the shear rate at temperature from 80 to 120°C. The zero shear viscosity (η_o) was obtained by using the simplified Cross model to fit experimental data. The η_o values were used for detailed viscosity‐concentration and activation energy analysis. The exponent in the viscosity‐concentration power law was found to be 3.63 at 80°C, which is comparable with cellulose dissolved in other solvents, and to be 5.14 at 120°C. The activation energy of the cellulose solution dropped from 70.41 to 30.54 kJ/mol with an increase of concentration from 10 to 25 wt %. The effects of temperature and concentration on the storage modulus (G′), the loss modulus (G″) and the first normal stress difference (N₁) were also analyzed in this study. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

两种咪唑型离子液体对纤维素的溶解及纺丝性能的比较

以1-乙基-3-甲基咪唑醋酸盐（[EMIM]Ac）和1-丁基-3-甲基咪唑氯盐（[BMIM]CI）两种咪唑型离子液体为溶剂,研究比较了它们对纤维素的溶解性能及其溶液的纺丝加工性能。结果发现：两种离子液体均能在一定条件下溶解纤维素,但[EMIM]Ac较[BMIM]Cl对纤维素具有更低的溶解温度和更快的溶解速率。从流变分析还发现：纤维素/[EMIM]Ac溶液与纤维素/[BMIMCl溶液均为切力变稀流体,相同条件下纤维素/[EMIM]Ac溶液的黏度远低于纤维素/[BMIM]Cl溶液,使其可在相对低的温度下纺丝。此外,GPC分析结果表明：纤维素在用[EMIM]Ac溶解及纺丝过程中降解程度较小,而用[BMIM]Cl进行溶解纺丝时,降解作用则较明显。对纤维结构与力学性能的分析结果进一步表明：与相同喷头拉伸比下制得的[EMIM]Ac法再生纤维素纤维相比,[BMIM]Cl法再生纤维素纤维的聚集态结构相对较完善,结晶度与取向度更高些,从而使其力学性能也相对较好。     

Rheological properties of cotton pulp cellulose dissolved in 1‐butyl‐3‐methylimidazolium chloride solutions

Rheological properties of cotton pulp dissolved in 1‐butyl‐3‐methylimidazolium chloride ([Bmim]Cl) solutions were characterized using an advanced rheometer. The complex viscosity, dynamic modulus, and shear viscosity at different temperature were studied. In the steady shear measurements, all the solutions show a shear‐thinning behavior at high shear rates. The complex viscosity as a function of frequency was fitted by extended Carreau–Yasuda model. In all cotton pulp/[Bmim]Cl solutions, the complex dynamic viscosity (η*) and steady shear viscosity (η_a) followed the Cox–Merz rule only at lower frequency. The effects of tested temperature on viscosity and viscoelastic behavior of the solutions were also investigated. The value of activation energy for the dissolution of cotton pulp in ionic liquids was 65.28 kJ/mol at the concentration of 10 wt% and was comparable with the ones for the dissolution of cellulose in NMMO. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Rheology of 1‐butyl‐3‐methylimidazolium chloride cellulose solutions. II. Solution character and preparation

The focus of this article of a three part series is the effects of preparation and composition on the shear rheology of cellulose in the ionic liquid 1‐butyl‐3‐methylimidazolium chloride ([Bmim]Cl). Included are the effects of three different degrees of polymerization, (i.e., average molecular weight), manual versus high shear mixing, a range of cellulose concentrations, and the effects of controlled amounts of lignin and a hemicellulose. The rheology implies that a gel phase develops at higher degrees of polymerization, higher concentration, and at lower temperatures. The first article focused primarily on shear rheology of cellulose in [Bmim]Cl with a high shear preparation technique, one degree of polymerization, a narrow range of cellulose concentrations, and temperature. The third article focuses on elongational rheology of cellulose in [Bmim]Cl. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The viscoelastic behavior of concentrated polyacrylonitrile/1‐butyl‐3‐methylimidazolium chloride from solution to gel

The viscoelastic behavior of concentrated polyacrylonitrile (PAN) /1‐butyl‐3‐methylimidazolium chloride ([BMIM]Cl) solutions at different concentrations and temperatures has been investigated by rheology. For concentrated polymer solutions at low temperature (40°C), the shear viscosity was found to show a raid decrease from the ending of Newtonian plateau. At relatively high shear rate or frequency for the concentrated PAN/[BMIM]Cl solutions, the deviation from the empirical Cox–Merz rule was quite evident, which suggested the formation of heterogeneous structures within these solutions. However, the dependence of G′ and G″ on angular frequency presented approximate linearity with similar slope at some temperatures between 100°C and 20°C. All the results lead us to the fact that the gelation has occurred within the concentrated solutions during cooling and the process was found to be thermoreversible. The gelation temperatures of the solutions have exhibited strong concentration dependence. It may be suggested that the microphase separation may be the major reason for the gelation of the concentrated PAN/[BMIM]Cl solutions during cooling process. POLYM. ENG. SCI., 54:598–606, 2014. © 2013 Society of Plastics Engineers     

Preparation and characterization of acrylic acid‐treated bacterial cellulose cation‐exchange membrane

The feasibility of using bacterial cellulose as a source for environmentally compatible ion‐exchange membranes (IEM) was studied. Bacterial cellulose was modified with cation‐exchangeable acrylic acid (AAc) by UV‐graft polymerization to prepare membranes having ion‐exchange capacity (IEC) and greater structural density. Fourier transform infrared (FTIR) spectra showed that acrylic acids were successfully bound to bacterial cellulose. Morphological changes of acrylic acid‐treated bacterial cellulose were examined through scanning electron microscopy. A dense structure of the membrane increased with increasing UV‐irradiation time. Acrylic‐modified bacterial cellulose membrane showed reasonable mechanical properties, such as tensile strength of 12 MPa and elongation of 6.0%. Also the prepared membranes were comparable to the commercial membrane CMX in terms of the electrochemical properties, ie IEC of 2.5 meq g^?1‐dry mem, membrane electric resistance of 3 ohm cm², and transport number of 0.89. Copyright © 2003 Society of Chemical Industry     

Structure and properties of cellulose fibers from ionic liquids

1‐Butyl‐3‐methylimidazolium chloride ([BMIM]Cl) was used as a solvent for cellulose, the rheological behavior of the cellulose/[BMIM]Cl solution was studied, and the fibers were spun with a dry‐jet–wet‐spinning process. In addition, the structure and properties of the prepared cellulose fibers were investigated and compared with those of lyocell fibers. The results showed that the cellulose/[BMIM]Cl solution was a typical shear‐thinning fluid, and the temperature had little influence on the apparent viscosity of the solution when the shear rate was higher than 100 s^?1. In addition, the prepared fibers had a cellulose II crystal structure just like that of lyocell fibers, and the orientation and crystallinity of the fibers increased with the draw ratio increasing, so the mechanical properties of the fibers improved. Fibers with a tenacity of 4.28cN/dtex and a modulus of 56.8 cN/dtex were prepared. Moreover, the fibers had a smooth surface as well as a round and compact structure, and the dyeing and antifibrillation properties of the fibers were similar to those of lyocell fibers; however, the color of these dyed fibers was brighter than that of lyocell fibers. Therefore, these fibers could be a new kind of environmentally friendly cellulose fiber following lyocell fibers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Diffusion dynamics of ionic liquids during the coagulation of solution spinning for acrylic fibers

The coagulation dynamics of acrylic polymer (PAN) with 1‐butyl‐3‐methylimidazolium chloride [BMIM]Cl as solvent for PAN and H₂O as nonsolvent was investigated in detail. On the basis of Fick's second law of diffusion, a mass‐transfer model of [BMIM]Cl from concentrated PAN/[BMIM]Cl solution was established as verified with the experimental data. The established model has a good fit with the experimental data and the diffusion coefficient D of [BMIM]Cl was calculated according to the model. The diffusion coefficient D decreased a little when the concentration of solution increased. As increasing the coagulation bath concentration, the diffusion coefficient D initially increased and then decreased, reaching a maximum of 5 wt% in the coagulation bath. The diffusion coefficient D decreased with the coagulation bath temperature. From the diffusion coefficient and the structure of the coagulated filament, it can be concluded that the diffusion rate of [BMIM]Cl from PAN concentrate solutions is relatively slow, which is prospective to prepare uniform‐structure fibers. POLYM. ENG. SCI., 48:184–190, 2008. © 2007 Society of Plastics Engineers     

以离子液体为溶剂的纤维素纤维的结构与性能

以离子液体氯化1-丁基-3-甲基咪唑([BMIM]Cl)为溶剂,制备了纤维素/[BMIM]Cl溶液,探讨了该体系的流变性能,并对所纺得的纤维素纤维的结构与性能进行了分析。结果表明:纤维素/[BMIM]Cl溶液为切力变稀流体,当剪切速率较大时,温度对体系黏度几乎没有影响,因此可以在较高剪切速率下降低纺丝温度;由该体系纺制的纤维具有纤维素II晶型的结构;随着拉伸比的提高,纤维的取向程度及结晶度增大,从而使纤维力学性能提高,所得纤维的表面光滑、结构致密,其染色性能及抗原纤化性能与Lyocell纤维基本相近。从而证明了用离子液体[BMIM]Cl所纺制的纤维素纤维性能良好,可望成为继Lyocell纤维之后的又一新型绿色纤维素纤维。     

凝固浴浓度对离子液体法纤维素纤维结构以及性能的影响

探讨了以离子液体1-丁基-3-甲基咪唑氯盐([BMIM]Cl)为溶剂制备的纤维素纤维纺丝工艺条件中凝固浴浓度对纤维结晶结构以及力学性能的影响。实验表明:在相同拉伸比和气隙条件下,凝固浴浓度对再生纤维素纤维的结构以及性能影响较大。随着凝固浴浓度的增加,纤维的结晶度和无定形取向都呈现先增大后减小的趋势,纤维的横向晶粒变小,拉伸强度、初始模量也呈先增大后减小的趋势。     

All-cellulose films with excellent strength and toughness via a facile approach of dissolution–regeneration

This study describes a green method for preparing all-cellulose nanocomposites through a dissolution and regeneration process. Cotton linter pulp was dissolved in 7 wt % NaOH/12 wt % urea aqueous solution precooled to −12°C. Self-assembly of cellulose molecules into nanostructured cellulose fiber is achieved by using water addition and controlling the temperature to regenerate cellulose. By changing the microenvironment of the cellulose solution, the morphology of the nanostructured cellulose fibers and the mechanical properties of the regenerated cellulose films can be tuned. Then, a series of regenerated cellulose films have been prepared and characterized from various aspects. Compared with other all-cellulose films in the literature, the regenerated all-cellulose nanocomposite films prepared in this work exhibited good optical transparency, thermal stability, and excellent tensile strength (up to 135 MPa) when the regeneration temperature was adjusted to 50°C. This work provided a green and promising approach to prepare high-performance and environmentally friendly all-cellulose nanocomposites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46925.     

Dissolution and utilization of chitosan in a 1‐carboxymethyl‐3‐methylimidazolium hydrochloride ionic salt aqueous solution

1‐Carboxymethyl‐3‐methylimidazolium hydrochloride ([IMIM–COOH]Cl), a new ionic salt, is proposed as a green, promising solvent for dissolving chitosan. However, because of the optimal dosage of chitosan dissolved in [IMIM–COOH]Cl, a 12 wt % [IMIM–COOH]Cl aqueous solution was selected as an optimum solvent system for dissolving chitosan. The structures of the original and regenerated chitosan were characterized by Fourier transform infrared spectroscopy and X‐ray diffraction analysis. Scanning electron microscopy was used to visualize the morphological features of the reconstituted chitosan membranes. Meanwhile, the absorbance, tensile strength, and breaking elongation of the chitosan membranes were measured. The results reveal that 10–11 wt % was an optimal chitosan concentration for preparing membranes. Furthermore, the adsorption capacity for Cu(II) ion of the chitosan membranes was increased with the chitosan concentration decreased from 12 to 8 wt %. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41965.     

皇竹草预处理制备新型再生纤维素膜

以农林废弃物皇竹草茎为原料,采用蒸汽爆破和乙醇自催化制浆的方式分离出纤维素,将其溶解在离子液体1-丁基-3-甲基咪唑氯代盐([bmim]Cl)中形成纤维素溶液并在水中再生得到纤维素膜。实验表明,汽爆采用1.55 MPa,维压5.45 min;乙醇制浆采用60%(V/V)乙醇溶液,160℃,维持2 h,可制备出α-纤维素含量达到92.65%,聚合度620,灰分低于0.3%的皇竹草纤维素。离子液体溶解并在水中再生的纤维素膜是一种无大孔结构的致密膜,其拉伸强度和断裂伸长率分别达到了165 MPa和5.90%,具有良好的液体渗透性能。