细菌纤维素在LiCl/DMAc溶剂体系中的溶解性能研究

纤维素经过活化后可以溶解在LiCl/DMAc溶剂体系中,研究了乙二胺活化对细菌纤维素溶解性能的影响,得到最佳活化条件;研究了LiCl的浓度、溶解温度和搅拌时间对溶解性能的影响,得到最佳溶解条件;研究了细菌纤维素在LiCl/DMAc极性溶剂体系中的溶解机理。     

LiCl/DMAc体系对蔗渣的溶解性

LiCl/DMAc体系是近年来日益受到重视的纤维素非水溶剂,但其溶解植物生物质,如蔗渣的情况却鲜有报道。本文从活化时间、固液比、LiCl浓度、加热时间及加热温度5个方面对LiCl/DMAc体系溶解蔗渣的行为进行研究。结果表明最佳溶解条件为:蔗渣160℃活化1h,烘干后取400mg与10%LiCl/DMAc溶液20mL按固液比1:50g/mL混合,160℃加热3h后,蔗渣溶解率可达81.8%。这为均相条件下利用蔗渣进行高效衍生化提供了有前景的发展方向。     

细菌纤维素在LiCI/DMAc溶剂体系中的溶解性能研究

纤维素经过活化后可以溶解在Lic1/DMAc溶剂体系中,研究了乙二胺活化对细菌纤维素溶解性能的影响,得到最佳活化条件;研究了LICl的浓度、溶解温度和搅拌时间对溶解性能的影响,得到最佳溶解条件;研究了细菌纤维素在LiCl/DMAc极性溶剂体系中的溶解机理。     

聚丙烯腈/棉纤维素薄膜的制备与性能研究

以N,N二甲基乙酰胺/无水氯化锂（DMAc/LiCl）为溶剂配置聚丙烯腈（PAN）和棉纤维素溶液,采用旋涂法制备不同比例的PAN/棉纤维素薄膜。通过旋转黏度计对PAN/棉纤维素共混溶液的表观黏度进行研究,采用X射线衍射仪、傅里叶红外光谱仪、电子万能试验机以及吸水性能测试对PAN/棉纤维素薄膜的结构和性能进行了研究。结果表明,共混溶液的表观黏度随着纤维素含量的增加逐渐增大;DMAc/LiCl溶剂对PAN和棉纤维素的溶解为直接溶解,没有发生衍生化反应;PAN和棉纤维素均保持各自结晶结构不变;当棉纤维素含量为2.0 %（质量分数,下同）时,复合薄膜的拉伸强度和断裂伸长率达到最大值;棉纤维素含量越高,复合薄膜的吸水性越好。     

在线红外跟踪碱活化纤维素在LiCl/DMAc中的溶解

LiCl/DMAc可作为纤维素的溶剂。笔者利用在线红外技术实时跟踪碱活化纤维素在LiCl/DMAc中的溶解过程。结果表明,LiCl/DMAc可以在一定程度上破坏纤维素中氢键,实现对纤维素的溶解,无中间衍生物产生,最终溶液中纤维素主要以多聚体形式存在。同时,检测出LiCl/DMAc对纤维素的高温预溶解与室温溶解过程,且此过程可逆。     

细菌纤维素在氢氧化钠―尿素水溶液体系中的溶解性能研究

纤维素经过活化、再生后可以溶解在氢氧化钠/尿素体系中。本文研究了乙二胺活化对细菌纤维素结晶度的影响规律,得到最佳活化条件;然后将活化后的细菌纤维素在LiCl/DMAc体系中溶解再生,得到再生细菌纤维素。最后,使用氢氧化钠/尿素溶液作为再生细菌纤维素的复合溶剂,得到的细菌纤维素的水溶液。通过红外光谱、X射线衍射仪、热重分析仪等分析了细菌纤维素不同处理阶段得到产物的性能。溶解与再生并没有发生化学变化,纤维素的结构基本保持不变,但结晶度有所降低,热稳定性有所提高。     

基于氯化钙溶液的混合盐溶液除湿剂物性测量

为了改善单一除湿盐溶液的性能,同时降低耗费成本,越来越多的学者致力于混合除湿盐溶液的研究。考虑以价格低廉但除湿效果一般的氯化钙溶液为基础溶液,添加氯化锂或溴化锂颗粒形成混合溶液来提高单一氯化钙溶液的除湿能力。测量了单一氯化钙溶液,加LiCl/LiBr颗粒后饱和混合溶液的质量浓度,探究极限溶解度,其次对氯化钙、氯化锂不同配比混合溶液在不同温度下的黏度及表面张力进行了测量。通过溶解度的实验测量,发现已经饱和的氯化钙溶液中还可继续溶解最高达8%的LiCl/LiBr晶体。测量得不同配比氯化锂、氯化钙混合溶液的黏度与表面张力值,通过比较发现氯化锂与氯化钙1：1的质量比下,混合溶液的黏度与表面张力均最低。     

蔗渣/LiCl/DMAc溶液体系及其纤维素接枝聚丙烯酰胺的制备

为了发展利用植物生物质资源,采用将蔗渣溶于LiCl/DMAc体系并利用溶解于其中的物质与丙烯酰胺进行均相接枝反应以制备蔗渣接枝聚丙烯酰胺。结果表明蔗渣在160℃活化1h,烘干后与100g/L的LiCl/DMAc体系以固液比1∶50混合,然后在160℃加热4h的条件下可以取得81.3%的溶解率。溶液中不但含有纤维素,而且含有半纤维素和木质素。该溶液在30℃、N2环境且丙烯酰胺分两次投料的条件下进行共聚的接枝率达到62.86%。进一步的实验表明蔗渣接枝物的主要成分是纤维素-g-聚丙烯酰胺。这为植物生物质的高值化利用提供了新的途径。     

棉纤维在NMMO溶液中的溶胀与溶解

用不同质量分数的N-甲基吗啉-N-氧化物(NMMO)溶液,在不同的温度和时间条件下,探究棉纤维的溶胀和溶解情况,并利用X射线衍射和红外光谱对纤维素溶胀前后的结构变化进行表征。结果表明:NMMO质量分数低于80%时,棉纤维只溶胀不溶解;在质量分数分别为83%、85%、87%的NMMO溶液中,棉纤维出现溶解现象;随着NMMO质量分数的增大、温度的升高、时间的延长,棉纤维的溶胀程度不断增加。在质量分数为83%的NMMO溶液中,棉纤维先溶胀后溶解;在质量分数为87%的NMMO溶液中,棉纤维不溶胀直接溶解;在质量分数为85%的NMMO溶液中,棉纤维的溶解存在先溶胀后溶解和直接溶解两种形式。质量分数为80%以下的NMMO水溶液处理后的棉纤维,结晶结构和化学结构均没有变化。     

纤维素在氯化锂/二甲基乙酰胺溶剂体系中的溶解实验

经过二甲基乙酰胺活化处理的纤维素,在温和的温度条件下,可以溶解在氯化锂/二甲基乙酰胺溶剂系中,得到较高浓度的透明溶液。纤维素原料先经晶内溶胀,再活化,可以大为提高溶解程度。溶剂体系中,氯化锂浓度大于一定值才能溶解纤维素,氯化锂浓度大,纤维素溶解度大。溶剂体系中含少量水,有利于纤维素的溶解,但含过量水的溶剂则失去溶解能力。适当升高溶解温度,可以加快纤维素溶解,但温度过高纤维素高度溶胀而不溶解。     

不同预处理条件下纤维素的结构变化及其在DMAc／LiCI中的溶解

介绍了乙二胺、氢氧化钠和高温等三种不同的纤维素预处理方法。研究预处理后纤维素的结构变化，讨论预处理过程中的转化机理，并通过X射线衍射对纤维素结晶度的变化进行表征，证明乙二胺预处理后纤维素的结晶度下降最大。纤维素经过预处理后可以溶解在DMAc／LiCI中，讨论其溶解机理，通过对比三种预处理纤维素的溶解性能，表明经过乙二胺预处理之后的纤维素在DMAc／LiCI中溶解性能最好，氢氧化钠预处理的纤维素次之，高温预处理的纤维素溶解性能相对较差。     

不同预处理条件下纤维素的结构变化及其在DMAc/LiCl中的溶解

介绍了乙二胺、氢氧化钠和高温等三种不同的纤维素预处理方法。研究预处理后纤维素的结构变化,讨论预处理过程中的转化机理,并通过X射线衍射对纤维素结晶度的变化进行表征,证明乙二胺预处理后纤维素的结晶度下降最大。纤维素经过预处理后可以溶解在DMAc/L iC l中,讨论其溶解机理,通过对比三种预处理纤维素的溶解性能,表明经过乙二胺预处理之后的纤维素在DMAc/L iC l中溶解性能最好,氢氧化钠预处理的纤维素次之,高温预处理的纤维素溶解性能相对较差。     

Recycling of waste cotton fabrics into regenerated cellulose films through three solvent systems: A comparison study

Large amounts of textile waste are generated every year and disposed of through landfill or incineration, leading to numerous environmental and social issues. In this work, the dissolution of three typical waste cotton fabrics (t-shirts, bed sheets and jeans) in NaOH/urea aqueous solution, H₂SO₄ aqueous solution, and LiCl/DMAc solution was investigated. Compared to different types of cotton fabrics, the effects of three solvents on the dissolution of fabrics were more obvious, leading to the significant changes in the structure and properties of regenerated cellulose films. Cotton fabrics (about 2%–5%) were rapidly dissolved (8 min) in H₂SO₄ and NaOH/urea solvents after acid pretreatment, while the dissolution in LiCl/DMAc solvent did not need any pretreatment, but a lower cellulose concentration (1%), higher dissolution temperature (80°C), and longer dissolution time (24 h) were required. The films produced from bed sheets in NaOH/urea solution exhibited the highest tensile strength, thermal stability, and water vapor barrier property. It was because of the stronger cellulose chain entanglement and hydrogen bonds induced by the higher cellulose concentration in NaOH/urea solution. Therefore, this work proves the feasibility to recycle waste cotton fabrics into biodegradable cellulose films, which can be potentially used in various food and agricultural applications.     

Aerocellulose based on all‐cellulose composites

Novel aerogels (or aerocellulose) based on all‐cellulose composites were prepared by partially dissolving microcrystalline cellulose (MCC) in an 8 wt % LiCl/DMAc solution. During this process, large MCC crystals and fiber fragments were progressively split into thinner crystals and cellulose fibrils. The extent of the transformation was controlled by using cellulose concentrations ranging from 5 to 20 wt % in the LiCl/DMAc solution. Cellulose gels were precipitated and then processed by freeze‐drying to maintain the openness of the structure. The density of aerocellulose increased with the initial cellulose concentration and ranged from 116 up to 350 kg m^?3. Aerocellulose with relatively high mechanical properties were successfully produced. The flexural strength of the materials reached 8.1 MPa and their stiffness was as high as 280 MPa. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

废旧涤棉面料组分溶解分离研究

采用离子液体[Amim]Cl对废旧涤棉混纺面料中含棉成分进行溶解回收。通过正交试验法,研究了温度、[Amim]Cl质量分数、时间、溶质与溶剂比例等因素对溶解过程的影响,得到优化的溶解工艺条件,同时研究了溶剂对涤纶的影响。结果表明:处理后的面料中接近99.2%的棉纤维被溶解,而涤纶没有明显损伤。影响棉纤维溶解效果因素的主次关系依次为:溶解温度,溶解时间,[Amim]Cl质量分数,溶质与溶剂质量比。优化的溶解工艺参数为:溶解温度95℃,溶解时间5 h,[Amim]Cl质量分数99%,溶质与溶剂质量比0.2∶3.5。红外分析表明:溶解处理的样品中棉的特征峰基本消失。     

Mild condition dissolution of high molecular weight cotton cellulose in 1‐butyl‐3‐methylimidazolium acetate/N,N‐dimethylacetamide solvent system

To investigate the effective dissolution of high molecular weight (MW) cellulose macromolecules at ambient conditions, cellulose (DP > 4,000) derived from cotton fiber waste was dissolved in 1‐butyl‐3‐methylimidazolium acetate (BMIMAc)/N,N‐dimethylacetamide (DMAc) solvent in this study. High MW cotton cellulose achieves a solubility between 3% and 5% cellulose concentrations using BMIMAc/DMAc solvent at ambient conditions. Rheological studies showed that all cellulose/solvent solutions displayed a shear thinning behavior. Results from the physical characterization revealed that well‐dissolved cotton cellulose exhibited highly porous structure and the crystalline structure of cotton cellulose was highly disrupted during dissolution and regeneration processes. This study is the first to report on the ability of BMIMAc/DMAc solvent system to dissolve high MW cellulose under ambient conditions, which represents an energy‐saving and environmentally friendly approach. As cellulose used in this study was derived from low quality waste cotton fibers, the potential utilization of such cotton cellulose may create a competitive market for low quality cotton and target advanced applications of cellulose‐based products for green materials and energy. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45928.     

Cellulose in lithium chloride/N,N-dimethylacetamide, optimisation of a dissolution method using paper substrates and stability of the solutions

Activation and dissolution in lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) of cellulose from paper substrates are studied. The importance of the multiple parameters involved such as salt concentration, sample source and preparation is shown in a literature review. The experiments are carried out in order to perfect the method of activation and dissolution of paper containing different kinds of additives, typically found in historic papers. The suitability and efficiency obtained in the different trials are evaluated. The final procedure involves the activation by solvent exchange, with a water/methanol/DMAc sequence, followed by dissolution in 8% LiCl/DMAc at 4 °C. A study of the stability of the cellulose solutions in the experimental conditions showed that no degradation nor aggregation occurred during the solvation process and even after several months and confirmed the non-aggressiveness of LiCl/DMAc.     

醋酸长链酸纤维素酯合成技术探索研究

以纤维素、醋酸酐和十二酰氯为原料在N,N-二甲基乙酰胺/氯化锂(DMAc/LiCl)溶剂体系中制备了醋酸月桂酸纤维素酯。考察了在不使用缚酸剂的条件下,反应物的加入顺序及加入量、纤维素溶液浓度、反应温度和反应时间对接枝率的影响,试验结果表明,在较优的工艺条件下,产物接枝率可达230%以上。