纤维素在ZnCl2水溶液中的溶解性能及其再生结构

本文比较了不同质量分数的ZnCl2水溶液溶解不同聚合度纤维素的能力,结果表明,质量分数为65％以下的ZnCl2水溶液由于其Zn2＋被完全水化作用而不能溶解纤维素,当达到或超过该浓度时,Zn2＋可与纤维素分子链作用,使纤维素溶解,且65％ZnCl2水溶液的溶解效果最佳;但随着纤维素聚合度的增大,其溶解度下降;本文研究还表明通过添加尿素可改善纤维素的溶液的流动性。经ZnCl2水溶液溶解后的再生纤维素的聚合度（DP）下降;x-射线衍射分析表明再生纤维素为纤维素Ⅱ结晶变体;红外分析结果显示ZnCl2水溶液是纤维素的非衍生化溶剂,且再生纤维素分子内氢键减弱。     

纤维素/磷酸/多聚磷酸液晶溶液的动态流变性能

纤维素可直接溶解在磷酸/多聚磷酸溶剂体系中形成液晶溶液,使用此溶液有希望制得高强、高模的纤维素纤维.用热台偏光显微镜观察了纤维素/磷酸/多聚磷酸液晶溶液的清亮点,通过动态流变实验研究了溶液在不同温度、不同纤维素质量分数、不同P2O5质量分数及不同纤维素聚合度(DP)下的流变特性.结果表明在溶液温度40℃以下,纤维素质量分数14%～15%左右,P2O5质量分数75%和纤维素聚合度(DP)1 000的条件下是适合液晶纺丝的理想条件,为探寻合适的纺丝工艺条件提供了理论基础.     

亚麻落麻再生纤维素纤维的制备及凝固浴对纤维结构与性能的影响

为探究不同凝固浴对再生纤维素纤维结构与性能的影响,用高浓度氯化锌(ZnCl2)溶液溶解亚麻落麻纤维,选取甲醇、乙醇、乙二醇、丙三醇和异丙醇溶液作为凝固浴,通过湿法纺丝工艺制备再生纤维素纤维,并对ZnCl2在不同凝固浴中的溶解度,以及再生纤维素纤维的表观形貌、化学结构、热稳定性及拉伸性能进行测试.结果表明:ZnCl2在5...     

NMMO法纤维素膜的制备及力学性能

利用NMMO(N-甲基吗琳-N-氧化物)溶解纤维素并制备纤维素包装膜,研究了不同浆粕种类、聚合度和工艺条件对纤维素膜力学性能的影响.结果表明:以聚合度为1 460的针叶木浆为原料,浆粕质量分数为7%,凝固浴中水的体积分数为100%,凝固浴温度为20℃.增塑剂中甘油体积分数为30%时可制得力学性能较好的纤维素膜.     

碱预处理对大麻秆浆纤维素性质的影响

采用氢氧化钠溶液对大麻秆浆进行预处理,研究了温度、氢氧化钠浓度、预处理时间对纤维得率、R-10值、聚合度、碘吸附值和纤维素晶型的影响。结果表明：低温下氢氧化钠溶液对分子质量较低的纤维素有较强的溶解能力,温度越低,纤维素可溶的分子质量分布越宽,且纤维素Ⅰ越易通过氢氧化钠溶液的润胀转变为纤维素Ⅱ。适当提高氢氧化钠溶液的浓度有助于浆料中半纤维素及低分子质量纤维素的溶解,有利于纤维素的充分润胀。当氢氧化钠质量分数超过9 %时,纤维素的晶型开始明显由纤维素Ⅰ转变为纤维素Ⅱ,导致可及度降低。在预处理时间为1~3 h时,预处理时间对纤维得率、R-10值、聚合度、碘吸附值及纤维素晶型等的影响不大。     

纤维素/壳聚糖/ZnCl2·4H2O溶液的制备及其流变性能

采用ZnCl2·4H2O溶液作为纤维素和壳聚糖的共同溶剂,制备纤维素/壳聚糖/ZnCl2·4H2O溶液,研究温度、原料组分和剪切频率等对纤维素/壳聚糖/ZnCl2·4H2O溶液流变性能的影响.研究结果表明：溶液中大分子链间缠结点在高温下更易打开,流动阻力下降;CS/BC分数增加时缠结作用强,流动阻力升高.故溶液的表观黏度、结构黏度指数、零切黏度、储能模量和损耗模量随着温度的升高而减小,随着壳聚糖/纤维素(CS/BC)分数的增加而增大;剪切频率增加,溶液的表观黏度减小,储能模量和损耗模量增大.     

生物质棉纤维再生纤维素膜的制备与性能分析

以天然生物质棉纤维为原料,采用氯化锂/N,N-二甲基乙酰胺(Li Cl/DMAC)溶解体系对其进行活化处理,配置不同质量分数的纤维素有机溶液系列,在不同凝固浴条件下,采用KW-4A匀胶机高速旋涂成膜和AFA-Ⅱ自动涂膜器低速平推成膜2种工艺,制备再生纤维素薄膜系列。通过运用扫描电镜(SEM)、傅里叶变换红外光谱(FT-IR)、X射线衍射仪(XRD)和表面接触角测试仪等分析设备对再生纤维素膜的大分子结构、力学性能、结晶度、热稳定性和表面浸润性进行各项性能的系列化表征,研究纤维素质量分数、凝固浴种类、制膜工艺对膜性能的影响。实验结果表明:采用KW-4A匀胶机高速成膜工艺、凝固浴为水浴、纤维素质量分数为3.5%时,制备的再生纤维素膜的各项性能最佳;与天然生物质棉纤维相比,再生纤维素膜结晶度变化很大,热稳定性与棉纤维变化趋势一致但有一定程度下降,表面浸润性良好。     

纤维素在NaOH/尿素/硫脲复合溶剂体系中的溶解性能研究

纤维素可溶于NaOH/尿素/硫脲复合溶剂体系.实验采用正交实验的方法研究了NaOH/尿素/硫脲的浓度对纤维素溶解的影响,以及各种溶解条件对溶解效果的影响.通过用XRD、FT-IR表征了该体系下所得的再生纤维素膜.结果表明:纤维素在该水溶液体系下的最佳溶解条件:NaOH的质量分数7%,尿素的质量分数7%,硫脲的质量分数10%,冷冻温度-10℃,在该条件下对纤维素有很好的溶解性能且纤维素溶解再生后为纤维素Ⅱ.     

纤维素在磷酸／多聚磷酸复合溶剂中的溶解性能

通过捏合机制备了纤维素在磷酸/多聚磷酸复合溶剂中的液晶溶液.主要研究纤维素质量分数、温度、复合溶剂中P2O5质量分数对纤雏素一磷酸/多聚磷酸溶液性能及溶解行为的影响.结果表明,液晶溶液的清亮点随P2Os质量分数及纤维素质量分数的增加而升高.溶解时间随P2O5质量分数的升高及温度的降低而增加.在此基础上,分析了磷酸/多聚磷酸溶剂与纤维素的相互作用并提出了纤维素在磷酸/多聚磷酸溶剂中的溶解过程及机理.     

离子液体中纤维素的溶解及再生特性

探讨了不同来源纤维素在离子液体1-丁基-3-甲基咪唑氯代盐(［bmim］Cl)中的溶解性能,并采用红外光谱、X-射线衍射及热重分析等手段对木浆纤维素在离子液体［bmim］Cl中溶解和再生前后的结构变化进行了分析。结果表明,未经活化的纤维素可直接溶解于离子液体［bmim］Cl 而不发生其它衍生化反应,原纤维素聚合度越低,溶解越容易。再生纤维素分子量较原纤维素有所降低,结晶状态由纤维素Ⅰ转变为纤维素Ⅱ,再生后纤维素热分解温度降低,热稳定性略有下降。     

The Dissolution of the Cellulose in the N - ethylmorpholine - N - oxide (NMMO) - Water System with Hydrothermolysis

Tbe N - methylmorpholine - N - oxide (NMMO) - water solvent was used to dissolve the cellulose that was achieved by means of hydrothermolysis. Sample B, RS and WS used here were made from beech, rice straw and wheat straw respectively. They could be completely dissolved in the NMMO - water system. A commercial a - cellulose was employed in the comparative experiment. The entire dissolving process was Investigated. At a given temperature, the vacuum condition applied to the mixture of the cellulose and NMMO - water was very important in order to accelerate the dissolution of cellulose and shorten the dissolving period. After dissolution, degree of polymerization (DP) of all samples was measured by viscometry. Longer dissolving time and higher temperature could cause the degradation of the dissolved cellulose. N- propyl gallate could prevent the degradation of cellulose during the process of dissolution.     

Effects of Coagulation Conditions on Tensile Properties of Regenerated Cellulose Fibers

The effects of coagulation conditions on tensile properties of the regenerated cellulose fibers prepared by wet-spinning from NaOH/thiourea/urea(8∶6.5∶8 by weight)aqueous solvent were investigated by tensile tester,X-ray diffraction(XRD),and scanning electron microscope(SEM).The results show that the tensile properties of the as-spun fibers change with the coagualtion concentration,temperature,and time.When the spinning solution is coagulated in 10% H2SO4/12.5% Na2SO4 aqueous solution,the as-spun fibers hav...     

Study on TEMPO-Mediated Selective Oxidation of Alkaline Natural Cellulose Pulp and Properties of Its Products

It has been reported that natural cellulose(celluloseⅠ) can not be oxidized by TEMPO - NaOCl -NaBr system, one of TEMPO-mediated selective oxidantsystems, but regenerated cellulose(cellulose Ⅰ)can becompletely selectively oxidized. In the present work,natural cellulose pulp was treated with NaOH solution,which concentration is lower than 20 wt%. The alkalinecelluloses obtained were oxidized by TEMPO - NaOCl -NaBr system and the factors which influence the selectiveoxidation reaction rate have been investigated. Thestructure of the oxidized products has been characterizedby Fourier transform-infrared(FTIR), nuclear magenaticresonace(NMR) and wide angle X-ray diffraction(WAXD) methods, and their adsorption properties forCu2 and Cd2 in aqueous solutions have beenpreliminarily examined. The results show that after thealkaline treatment, the primary hydroxyl at C6 position ofnatural cellulose can be selectively oxidized to carboxylgroup in the reaction medium at pH 10.8, the oxidationrate becomes greater with the NaOH concentration andalkaline treatment time increasing. The alkaline treatmenthas a great effect on the crystal structure of naturalcellulose, but the crystal structure of alkaline cellulosekeeps almost unchanged after oxidation. The adsorptioncapacity is enhanced by introducing carboxyl groups intothe cellulose macromolecular chains.     

双螺杆工艺纤维素溶解方法初探

讨论了制备Lyocell纤维过程中的溶解工艺。该工艺采用混合器先将NMMO和纤维素在低温下进行预混,得到均匀的预混和物,然后经双螺杆溶解,其溶解时间短,能耗少,工艺简单,减少了溶剂分解和纤维素降解的可能性。该工艺制得的溶液色浅、溶解完全且不含气泡,可以直接用来纺丝。     

Solubility Behaviour of Cellulose in a Sodium Hydrate/Urea/Thiourea Aqueous Solvent

Cellulose pulps were directly dissolved in a green solvent of sodium hydrate/urea/thiourea/water with different composition for the purpose to prepare new regenerated cellulose fibers or films. The results showed that the highest solubility of cellulose in the solvent with the composition of 8/8/6.5/77.5. The results revealed that the pulp feeding sequence, stirring rate, pre-treatment of pulp and pulp size affected the cellulose concentration in the green solvent. Accordingly, the more effective dissolution method was proposed in order to get higher concentration of cellulose. Furthermore, the properties of solution prepared by different kinds of pulps in the solvent were investigated by ARES rheometer. Rheologieal analyses indicated that all cellulose aqueous solutions in their high concentration were pseudoplastic fluids and sensitive to temperature and tended to transform to gel when temperature increased.     

纤维素／NMMO溶液溶解方法及其溶液的表征

Lyocell工艺中浆粕的溶解是十分关键的步骤,纺丝溶液的质量直接影响到该溶液的可纺性和丝的质量。本文讨论了有关溶解工艺的一些特点,特别着重介绍了目前国外一些公司的溶解方法,并结合本课题组的一些研究经验,提出了有关表征溶液质量的一些方法。     

预处理对纤维素微结构和反应性能影响的研究

本文研究用乙二胺、乙醇胺、ZnCl_2和NaOH水溶液、水-丙酮-NaOH系统、液氨分别预处理棉绒浆粕以及这些化学试剂对纤维素纤维微细结构和反应性能的影响。用X-射线衍射方法研究纤维素纤维原纤间和原纤内润胀的机理,证明经由化学活化处理,纤维的微细结构发生很大变化,可及度和反应性能得到相当大的提高,这一机理可进一步应用于纤维素纤维的酯醚化反应和其他改性。     

微晶纤维素/1-丁基-3-甲基咪唑氯体系流变性能研究

离子液体1-丁基-3-甲基咪唑氯(BmimCl)可用作溶解微晶纤维素(MCC)的优良溶剂。通过稳态剪切和动态扫描测试考察了微晶纤维素离子液体溶液的流变性能。结果表明,所有浓度的MCC/BmimCl溶液在高剪切速率和低剪切速率表现出剪切变稀行为。温度和浓度对MCC/BmimCl溶液的黏弹性质产生重要影响。将复合黏度数据用于Cross模型,并利用Arrhenius公式计算了不同浓度MCC/BmimCl溶液的流动活化能。