不同溶解方法制备的纤维素/[BMIM]Cl纺丝液的性能比较

以离子液体1-丁基-3-甲基咪唑氯盐([BMIM]Cl)为溶剂,分别采用直接溶解法和间接溶解法(即在含水[BMIM]Cl中溶胀后再减压蒸馏去除多余的水使之溶解)制备了纤维素/[BMIM]Cl纺丝液,系统地比较了这两种纺丝液的流变行为及可纺性。结果表明:相同条件下,直接溶解法制备的纤维素/[BMIM]Cl纺丝液的表观黏度最大,而间接溶解法制得的纺丝液的表观黏度随着溶胀时[BMIM]Cl的初始含水率的增加而下降。与直接溶解法相比,间接溶解法制得的纺丝液溶解均匀、流动性能好、纺丝过程中断头次数少、可纺性能提高,所得到的再生纤维素纤维具有更好的力学性能。     

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。     

Regenerated cellulose membrane prepared with ionic liquid 1‐butyl‐3‐methylimidazolium chloride as solvent using wheat straw

BACKGROUND: Currently, cellulose membranes are prepared by cellulose acetate hydrolysis or chemical derivatization dissolution and regeneration using cotton pulp or wood pulp. In this study, the concept ‘lignocelluloses biorefinery’ was used, and good quality long fiber was fractionated from wheat straw using clean technologies. The objective of this study is to develop wheat straw cellulose to prepare regenerated cellulose membrane with ionic liquid 1‐butyl‐3‐methylimidazolium chloride ([BMIM]Cl) as solvent. RESULTS: Wheat straw cellulose (WSC) fractionated from wheat straw contained 93.6% α‐cellulose and the degree of polymerization (DP) was 580. WSC was dissolved directly without derivatization in [BMIM]Cl. With increase in dissolving temperature, the DP of the regenerated cellulose dropped, which resulted in a decrease in the intensity of regenerated cellulose membrane. After regeneration in [BMIM]Cl, the WSC transformed from cellulose I to cellulose II, and the crystallinity of the regenerated cellulose was lower than the original cellulose. The regenerated WSC membrane had good mechanical performance and permeability, the tensile strength and breaking elongation were 170 MPa and 6.4%, respectively, the pure water flux was 238.9 L m^?2 h^?1 at 0.3 MPa pressure, and the rejection of BSA was stabilized at about 97%. CONCLUSION: Wheat straw cellulose fractionated from wheat straw satisfied the requirement to prepare regenerated cellulose membrane using ionic liquid [BMIM]Cl as solvent. Copyright © 2012 Society of Chemical Industry     

纤维素在离子液体水溶液中的溶胀与溶解行为的研究

以含水的离子液体1-丁基-3-甲基咪唑氯盐([BMIM]C)l为溶剂,研究了纤维素在其中的溶胀和溶解行为。通过偏光显微镜观察发现,[BMIM]Cl水溶液中的含水率对纤维素浆粕的溶胀与溶解行为有着重要的影响,主要表现为三种状态:当[BMIM]Cl中含水率小于1%时,浆粕纤维横向被迅速切断并快速溶解,没有发现明显的溶胀现象;当[BMIM]Cl中含水率在2%～5%时,浆粕纤维发生了非常明显的非均相溶胀,但并不溶解;而当[BMIM]Cl中含水率进一步增大到6%～20%时,浆粕纤维不再发生明显的溶胀现象。此外,研究结果还表明,当[BMIM]Cl中含水率在2%～5%时,溶胀温度和[BMIM]Cl中的含水率对于纤维素的溶胀有很大影响,随着温度升高,浆粕纤维的溶胀速度增大,达到最大溶胀比所需要的时间缩短;而随着[BMIM]Cl中含水率的提高,浆粕纤维在[BMIM]Cl水溶液中达到的最大溶胀比减小。     

MWCNTs含量对纤维素/[BMIM]Cl溶液及其纤维性能和形态结构的影响

分析了经表面功能化的MWCNTs(多壁碳纳米管)在纤维素/[BMIM]Cl(1-丁基-3-甲基咪唑氯盐)体系中的分散稳定性,探讨了MWCNTs/纤维素/[BMIM]Cl溶液的流变行为,并通过干湿法制备了不同MWCNTs含量的离子液体法纤维素纤维,对其力学性能和表面形态结构进行了研究。结果表明:MWCNTs/纤维素/[BMIM]Cl溶液为切力变稀流体。随着溶液中MWCNTs添加量的增加,溶液表观黏度先增大后减小;适量的MWCNTs可以均匀分散在纤维素/[BMIM]Cl溶液体系中并具有良好的可纺性,所制得的MWCNTs/纤维素纤维表面较光滑且力学性能明显改善。其中,含1%MWCNTs的纤维素纤维的初始模量和断裂强度较高,分别比未添加MWCNTs的纤维提高66.7%和22.7%。     

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。     

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     

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...     

Characteristics of polyacrylonitrile solutions and fibers varied with the dissolution process in ionic liquid

The concentrated polyacrylonitrile (PAN) solutions were prepared with 1‐butyl‐3‐methylimidazolium chloride ([BMIM]Cl) as solvent by static state, stirring, and kneading. The steady and oscillatory shear tests were carried out to investigate the viscoelastic behaviors of the PAN/[BMIM]Cl solutions by rotational rheometer. It was found that the zero shear‐rate viscosity and relaxation time of the solution prepared by kneading were lowest and the non‐Newtonian index was largest among the solution. During kneading, the gelation temperature of the viscous and homogenous solution was at the lowest temperature 22.7°C among the all three solutions. Only the solutions prepared by stirring and kneading could be spun by dry‐jet wet spinning technology. The fiber processed with the solution prepared by kneading could be drawn with a higher draw ratio, showing the larger draw ability. The supramolecular structure and properties of the fibers were studied by synchrotron wide‐angle X‐ray diffraction (WAXD) technologies, dynamic mechanical analysis (DMA), and mechanical tests. All the results showed that the kneading is an efficient method for PAN fiber spinning with [BMIM]Cl as solvent. It lead to the investigation of the methods of preparation of PAN solution in [BMIM]Cl, which affect the homogeneity of the solutions and hence the resulting characteristics of PAN fibers. POLYM. ENG. SCI., 55:558–564, 2015. © 2014 Society of Plastics Engineers     

Wet spinning of cellulose from ionic liquid solutions–viscometry and mechanical performance

A series of regenerated cellulose fibers was produced from dopes prepared by mixing and dissolving cellulose of two different degrees of polymerization in different ratios in the ionic liquid 1‐ethyl‐3‐methyl‐imidazolium acetate. Viscoelastic properties of the spin dopes were characterized by controlled stress rheometry. The cellulose solutions were solidified in pure water by the traditional wet spinning technique. The resulting fibers were characterized by means of wet and dry tensile testing and scanning electron microscopy. The characterization revealed a compact and homogeneous fiber. A nonlinear relationship between degree of polymerization and fiber properties was observed with a moderate difference in mechanical properties in a broad interval of fibers while fibers composed of polymers with the highest degree of polymerization stood out as stronger and stiffer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

纺丝工艺对离子液体法新型纤维素纤维性能的影响

以离子液体1-丁基-3-甲基咪唑氯盐（[BMIM]C1）为溶剂,用干湿法纺丝制备了再生纤维素纤维,通过正交试验设计和系统试验,考察了气隙长度、喷头拉伸比、凝固浴浓度和凝固浴温度等工艺参数对制得的再生纤维素纤维的力学性能的影响,找出离子液体法新型纤维素纤维的最佳纺丝工艺。试验结果表明,对于该体系,纺丝工艺参数中凝固浴温度和拉伸比对纤维的拉伸强度、初始模量的影响最大,气隙长度对纤维断裂伸长影响最大。     

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.     

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     

Cellulose nanofibers prepared by the N‐methylmorpholine‐N‐oxide method

The process of electrospinning is very suitable for obtaining fibers with a diameter on a nanometer scale. Such fibers can be spun from almost all kinds of known polymers, copolymers, and polymer blends. In this work, we present cellulose nanofibers obtained by the electrospinning process from spinning dopes containing cellulose dissolved in an N‐methylmorpholine‐N‐oxide/water system. Under different electrospinning process conditions, cellulose fibers, a nonwoven fiber network, and a cellulose membrane were obtained. The fibers were examined with scanning electron microscopy. The diameters of the fibers were in the submicrometer range. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1855–1859, 2005     

Comparison of direct solvents for regenerated cellulosic fibers via the lyocell process and by means of ionic liquids

Because new technology using ionic liquids (ILs) for cellulose processing enables the spinning of cellulose with various techniques, the resulting fiber property profiles differ significantly, depending on the process parameters. ILs are thermally stable, nontoxic, environmentally friendly solvents and dissolve cellulose directly; this leads to a high flexibility in the complete process chain for man‐made cellulosics. A comparison of the manufacture of cellulosic fibers according to the Lyocell process and by means of ILs is presented. The rheological behavior of the spinning dopes, the structures, and the physical textile properties of the prepared fibers were determined. The fibers spun from solutions of cellulose in N‐methyl morpholin‐N‐oxide monohydrate, 1‐ethyl‐3‐methyl imidazolium acetate, and 1‐ethyl‐3‐methyl imidazolium diethyl phosphate were compared. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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。     

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。     

Preparation and properties of chemical cellulose from ascidian tunic and their regenerated cellulose fibers

Chemical cellulose (dissolving pulp) was prepared from ascidian tunic by modified paper‐pulp process (prehydrolysis with acidic aqueous solution of H₂SO₄, digestion with alkali aqueous solution of NaOH/Na₂S, bleaching with aqueous NaOCl solution, and washing with acetone/water). The α‐ cellulose content and the degree of polymerization (DPw) of the chemical cellulose was about 98 wt % and 918, respectively. The Japanese Industrial Standard (JIS) whiteness of the chemical cellulose was about 98%. From the X‐ray diffraction patterns and ¹³C‐NMR spectrum, it was found that the chemical cellulose obtained here has cellulose Iβ crystal structure. A new regenerated cellulose fiber was prepared from the chemical cellulose by dry–wet spinning using N‐methylmorpholine‐ N‐oxide (NMMO)/water (87/13 wt %) as solvent. The new regenerated cellulose fiber prepared in this study has a higher ratio of wet‐to‐dry strength (<0.97) than commercially regenerated cellulose fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1634–1643, 2002.     

离子液体法新型再生纤维素纤维的研究

采用离子液体1-乙基-3-甲基咪唑醋酸盐([EMIM]Ac)为溶剂,制备了纤维素/[EMIM]Ac溶液,研究了该体系的流变性能,利用干喷湿纺的方式制备的新型再生纤维素纤维,并对纤维的结构与性能进行了分析。结果表明,纤维素/[EMIM]Ac溶液为典型的切力变稀流体,在较高剪切速率下,纺丝溶液的黏度变化较小;由该体系制备的新型再生纤维素纤维具有纤维素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,纤维力学性能提高。以离子液体为溶剂制备的再生纤维素纤维表面光滑,质地紧密。     

溶解方式对聚丙烯腈-离子液体溶液和纤维的影响

通过静置、搅拌和捏合3种不同的溶解方式制备了聚丙烯腈(PAN)质量分数为13%的PAN-[BMIM]Cl(1-丁基-3-甲基咪唑氯盐)溶液。采用旋转流变仪研究了这3种溶液的流变特性,发现捏合溶解得到的溶液的零切黏度与松弛时间最小,非牛顿指数最大,溶液性质均一稳定。利用制备的纺丝溶液进行干喷湿纺试验,发现静置溶解的纺丝溶液无法纺丝,而捏合溶解的纺丝溶液可实现较高倍数的喷头拉伸和水浴拉伸。结合广角X射线衍射(WAXD)、力学性能测试、动态力学分析(DMA)等测试方法,对比分析了两种溶解方法制备的PAN纤维的超分子结构和性能,发现捏合溶解纺丝得到的纤维结构更为均匀,力学性能更好。