Effect of carboxymethyl cellulose on dissolution kinetics of carboxymethyl cellulose-sodium carbonate two-component tablet

Sodium carbonate and carboxymethyl cellulose powders are compressed into two-component tablets with three mass ratios,97%:3%,95%:5% and 93%:7%.The dissolution tests for two-component tablets and reference pure sodium carbonate tablets are carried out at various temperatures.The dissolution process of each tablet is measured by electrical conductivity tracking method and the concentration of dissolved sodium carbonate is quanti fied with calibrated conductivity-concentration converting equation of sodium carbonate.The quanti fied dissolution data is fitted with both surface reaction model and diffusion layer model and the results clearly show that surface reaction model is suggested as the appropriate dissolution model for all measured tablets.Therefore,it is determined that carboxymethyl cellulose is a stable element to remain the dissolution mechanism of tablet unchanged.The dissolution rate constant quanti fied with surface reaction model presents that carboxymethyl cellulose-sodium carbonate two-component tablets obtain signi ficant higher dissolution rate constant than pure sodium carbonate tablet and higher proportion of carboxymethyl cellulose leads to apparent higher dissolution rate constant.The results prove for the usage of carboxymethyl cellulose in most practical applications at a relative low-level,the effect of carboxymethyl cellulose is effective and positive for two-component tablet to enhance the dissolution process and improve dissolution rate constant and this effect is speculated coming from its dynamic physical transforming process in water including dilation and conglutination.

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.

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.

An Alternative Strategy to Obtain Cellulose Nanofibrils from Parenchyma Cellulose of Bagasse Pith and the Performance of Its Nanopaper

Cellulose nanofibrils(CNFs)were obtained through one-step mechano-partial dissolution by ball milling in N,N-dimethyl acetamide with a low concentration of LiCl from agricultural waste bagasse pith(BP).Compared with fibrous cellulose,parenchyma cellulose(PC)is less uniform in diameter and less aligned,causing PC to dissociate into CNFs during this process without pretreatment.The results showed that the CNFs prepared from PC of BP had a diameter of 30-200 nm and a length of several micrometers.The as-obtained CNFs,along with dissolved cellulose,formed a wet-stable and highly transparent nanopaper in a sorbitol aqueous solution bath,which exhibited a high strain of 101%and a low Young's modulus of 4.3 MPa owing to the addition of the plasticizer sorbitol.This type of nanopaper with favorable transparency,high tensile property,and low Young's modulus has great potential for use as electronic skin and medical dressing material.

Graft copolymerization of cellulose and 2-hydroxyethyl methacrylate in an ionic liquid

Dissolution and homogeneous graft copolymerization of cellulose were performed in an ionic liquid 1-allyl-3-methylimidazolium chloride （AmimCl） with 2-hydroxyethyl methacrylate. The synthesized AmimCl and cellulose graft copolymers were characterized by FTIR, ^1 H-NMR and XRD spectroscopy. The results show that AmimCl dissolved cellulose directly by destroying intermolecular and intramolecular hydrogen bonds in cellulose and the crystalline form of cellulose was transformed from cellulose Ⅰ to cellulose Ⅱ after regeneration from AmimCl. The best synthetic condition of the cellulose-graft-P （2-hydroxyethyl methacrylate） was that cellulose 0.5 g, 2-hydroxyethyl methacrylate 3.00 g and initiator ammonium persulfate 0.05 g reacted for 180 min at 60℃; the rate of grafting reached 77.3%.

Understanding cellulose dissolution： effect of the cation and anion structure of ionic liquids on the solubility of cellulose

The effect of ionic liquids(ILs) on the solubility of cellulose was investigated by changing their anions and cations. The structural variation included 11 kinds of cations in combination with 4 kinds of anions. The interaction between the IL and cellobiose, the repeating unit of cellulose, was clarified through nuclear magnetic resonance(NMR) spectroscopy. The reason for different dissolving capabilities of various ILs was revealed. The hydrogen bonding interaction between the IL and hydroxyl was the major force for cellulose dissolution. Both the anion and cation in the IL formed hydrogen bonds with cellulose. Anions associated with hydrogen atoms of hydroxyls, and cations favored the formation of hydrogen bonds with oxygen atoms of hydroxyls by utilizing activated protons in imidazolium ring. Weakening of either the hydrogen bonding interaction between the anion and cellulose, or that between the cation and cellulose, or both, decreases the capability of ILs to dissolve cellulose.

Which is the determinant for cellulose degradation in cooperative ionic liquid pairs: dissolution or catalysis?

Catalytic conversion of sustainable cellulose to the value-added chemicals and high quality biofuel has been recognized as a perfect approach for the alleviation of the dependence on the non-renewable fossil resources. Previously, we successfully de- signed and explored novel and efficient cooperative ionic liquid pairs for this renewable material, which has advantages of high reactor efficiency than current technologies because of the dissolution and in situ catalytic decomposition mechanism. Here, the determinant of this process is further studied by the intensive investigation on the relationship between the cellulose conversion and the properties of ionic liquid catalyst and solvent. Scanning electron microscope （SEM）, thermogravimetric analysis （TG） and elemental analysis were used for the comparative characterization of raw cellulose and the residues. The re- suits demonstrate that this consecutive dissolution and in situ catalysis process is much more dependent on the dissolution ca- pability of ionic liquid solvent, while comparatively, the effect of in situ acid catalysis is relatively insignificant.

Dissociation of intra/inter-molecular hydrogen bonds of cellulose molecules in the dissolution process:a mini review

Cellulose is abundant in nature,with the advantages of low-cost,biodegradable and biocompatible,low density and high strength.However,the development and application of cellulose has been lagging behind its potential due to its unique properties.Cellulose has a large quantity of hydroxyl groups which can easily form hydrogen bond networks.The huge hydrogen bond network makes it extremely difficult to dissolve or melt cellulose,thus limiting the effective use of cellulose resources.To dissolve cellulose,the key is to break the hydrogen bonds.This article sums up recent studies on the dissociation or breakage of the intramolecular and intermolecular hydrogen bonds in the dissolution of cellulose.

The effect of hydrogen bond acceptor properties of ionic liquids on their cellulose solubility

It is nowadays well-known that ionic liquids can dissolve cellulose. However, little systematic data has been published that shed light onto the influence of the ionic liquid structure on the dissolution of cellulose. We have conducted 1H NMR spec- troscopy of ethanol in a large number of ionic liquids, and found an excellent correlation of the data obtained with the hydro- gen acceptor properties （B-values）. With this tool in hand, it is possible to distinguish between cellulose-dissolving and non-dissolving ionic liquids. A modulating effect of both, the anion of the non-dissolving ionic liquid and its cation was found in solubility studies with binary ionic liquid mixtures. The study was extended to other non-dissolving liquids, namely water and dimethylsulfoxide, and the effect of the cation was also investigated.

Cellulose Solubility in Deep Eutectic Solvents:Inspecting Quantitative Hydrogen-Bonding Analysis

According to the Kamlet-Abraham-Taft(KAT)polarity parameters(α,β,π*),polymers and solvents can be categorized as hydrogen-bond(H-bond)acidic(α>β)or H-bond basic(α<β).Recently,we proposed a quantitative hydrogen bonding(QHB)analysis to predict the solubility of polymers in ionic liquids(ILs)using the product ofΔαΔβ<0 as an indicator,whereΔαis the difference between the H-bond acidic parameters of the polymer and IL,andΔβis the difference in their basicity,while the prerequisite of the“complementary”principle(i.e.,that one component is H-bond acidic and the other is basic)is satisfied.Here,the applicability of QHB analysis was first confirmed by testing the solubilities of carefully chosen polymer/deep eutectic solvent(DES)pairs,as the DESs were eutectic mixtures dominated by hydrogen bonding interactions.Then,our attention focused on the solubility of cellulose in DESs.Our testing results as well as the typical published results were summarized,which indicate that the potential DESs for cellulose dissolution and regeneration must be of the H-bond basic type because the“complementary”principle should be satisfied as a prerequisite.However,the H-bond basic DESs investigated in this study do not show the superior solubility of cellulose that has been commonly observed for H-bond basic ILs,even if the criterion ofΔαΔβ<0 is satisfied for both DESs and ILs.Possible reasons for this discrepancy are given to understand the varying effectiveness in cellulose dissolution for H-bond basic DESs and ILs.

Hydrogen bond producers in powerful protic ionic liquids for enhancing dissolution of natural cellulose

The manipulation of hydrogen bonding within protic ionic liquids is conducive to conquering the robust hydrogen bonding interactions in cellulose for its effective dissolution,but it is a great challenge to establish the delicate bal-ance of hydrogen bonding network between solvent and cellulose.Herein,we proposed the concept of“hydrogen bond producers”for urea molecules in 1,1,3,3-tetramethylguanidinium methoxyacetate acid([TMGH][MAA])to enhance the dissolution of cellulose.The optimization of physicochemical properties for[TMGH][MAA]solvent as a function of urea concentration revealed a remark-able increase in cellulose solubility from 13%to 17%(w/w)by adding only 0.25 wt%urea,highlighting the efficiency of[TMGH][MAA]as a power-ful solvent for the dissolution of cellulose.The experimental and simulation results verified that the significant improvement on dissolution of cellulose was attributed to the hydrogen bonding interaction of urea molecules with ion pairs and part of free ions,reducing the interference with the active ions bonded to cellulose.Furthermore,the considerable enhancement on compre-hensive properties of regenerated cellulose films demonstrated the effectiveness of[TMGH][MAA]/urea solvent.The concept of“hydrogen bond producers”presented here opens a new avenue for significantly enhancing the dissolu-tion of natural cellulose,promoting the sustainable development in large-scale processing of cellulose.

离子液体中纤维素与废旧羊毛的溶解与再生

本研究以离子液体1-烯丙基-3-甲基咪唑氯盐([AMIM]Cl)为溶剂,以去离子水为凝固浴,对纤维素浆粕与废旧羊毛的溶解与再生过程进行了研究。采用偏光显微镜观察了纤维素和羊毛的溶解过程,研究了不同温度对它们溶解性能的影响以及纤维素及羊毛在不同温度下的溶解性能。通过傅里叶红外光谱(FTIR)、X射线衍射(XRD)及热重分析(TGA)等对其再生物进行了结构表征与性能测试。结果表明,[AMIM]Cl在一定条件下能够有效地同时溶解纤维素浆粕和废旧羊毛,且纤维素的加入有助于废旧羊毛再生为膜状材料,此外,所制备的再生纤维素/羊毛共混膜展现出更为优异的热稳定性。

微晶纤维素在季铵碱水溶液中的低温溶解研究

选用四甲基氢氧化铵(TMAH)、四乙基氢氧化铵(TEAH)、四丙基氢氧化铵(TPAH)3种季铵碱水溶液为溶剂,通过低温冷冻、室温解冻溶解微晶纤维素(MCC),研究不同温度及不同溶剂浓度下MCC的溶解效果,对不同季铵碱水溶液处理后的MCC的溶解行为进行表征。结果表明:随着冻融温度的降低,3种溶剂中MCC的溶解度整体上均呈现先上升后慢慢趋于稳定的趋势;在不同溶剂体系下,随着季铵碱浓度的增大,MCC的溶解度均呈现上升趋势;当冻融温度为-30℃、溶剂中季铵碱质量分数为35%时MCC的溶解效果最佳,在TMAH、TEAH和TPAH水溶液中MCC的溶解度分别为1.2%、11.5%和7.25%;季铵碱水溶液体系为MCC的非衍生化溶剂体系,其中TEAH能够削弱MCC内部氢键,溶解能力最强;经TEAH、TPAH处理的MCC的结晶度均下降,其中TEAH溶胀处理后MCC的结晶度由63.11%下降到43.71%,TEAH溶解后再生MCC的结晶度下降到30.46%,MCC的晶型由纤维素I晶型转变为纤维素II晶型;3种季铵碱水溶液中TEAH去结晶能力最强,对MCC的溶解效果最好。

棉浆纤维素/质子型离子液体溶液的流变行为

为实现棉浆纤维素的绿色、高效溶解,促进其高值化利用,以质子型离子液体([DBNH][Lev])为溶剂,制备了5种不同质量分数的纤维素/[DBNH][Lev]溶液;借助核磁共振技术研究了纤维素在离子液体中的溶解机制,测定了纤维素溶液在不同条件下的稳态和动态流变行为,讨论了纤维素含量、温度和剪切速率等对均相聚合物溶液黏度的影响规律。结果表明:纤维素/[DBNH][Lev]溶液为典型的假塑性流体,对温度具有敏感性,且黏度随温度升高而降低;此外,该溶液在高频率下出现凝胶点,存在黏性流动为主的类液态向弹性形变为主的类固态转变,且温度越高转变点越向低频区移动,这为纤维素在离子液体中的流变响应提供理论基础,并对后续的纤维素加工工艺(如涂层、纺丝)提供技术指导。

转酯化法制备芦苇基醋酸纤维素的工艺研究

以芦苇纤维素为原材料,在以1,8-二氮杂二环十一碳-7-烯(DBU)为催化剂,醋酸异丙烯酯(IPA)或乙酸乙烯酯(VA)为乙酰化试剂,二甲基亚砜(DMSO)为溶剂的条件下,对芦苇纤维素进行转酯化反应制备芦苇基醋酸纤维素。探讨了不同试验条件对芦苇基醋酸纤维素聚合度及取代度的影响,并通过聚合度测定、酸碱滴定取代度测定及红外光谱分析等手段进行表征。结果表明,在以IPA作为乙酰化试剂,DMSO作为溶剂,DBU作为催化剂,反应时间为4.5 h,反应温度为110℃时所制备的芦苇基醋酸纤维素最佳;所制芦苇基二醋酸纤维素的聚合度可达483.63,取代度可达2.41。

基于分子动力学的NMMO对纤维素Iβ结构与氢键影响研究

纤维素具有可降解性,基于纤维素改性材料的研发对纺织服装产业的可持续发展有重要意义。由于纤维素晶体中含有大量氢键,导致纤维素的溶解性比较差,因此,在一定程度上阻碍了不同功能纤维素的发展。NMMO是一种绿色溶剂,通过与纤维素的相互作用,破坏纤维素的氢键,促进纤维素溶解。为了更加全面地分析NMMO对纤维素的溶解机制,利用分子动力学方法,通过讨论纤维素在NMMO溶剂环境中,讨论NMMO对纤维素结构的影响,以及NMMO与纤维素链内、链间之间的相互作用,进一步丰富纤维素溶解机制。研究表明:NMMO通过破坏纤维素链内与链间氢键网络,且对纤维素链间氢键的破坏程度大于对链内氢键的破坏程度,促使纤维素链从其晶体区域逐步剥离,纤维素的结构稳定性被破坏,有效促进了纤维素的逐步溶解。

纤维素电纺纳米纤维柔性表皮电极制备与性能

【目的】为了解决当前可穿戴电极材料的生物不相容性、低响应集成特性等问题,本研究采用天然纤维素为原料,结合新型溶解技术与静电纺丝技术,通过原位聚合导电高分子制备纤维素电纺纳米纤维柔性表皮电极,并探究其在人体电信号监测领域的应用。【方法】将纤维素溶解于新型离子液体复合溶剂中,构建低黏度、长期稳定的纺丝液;采用室温静电纺丝法结合预凝固过程制备再生纤维素基电纺纳米纤维;通过与导电材料聚(3,4-乙烯二氧噻吩)-聚(苯乙烯磺酸盐)(PEDOT:PSS)复合进行纳米自组装,得到柔性表皮电极。采用扫描电镜、全自动比表面和孔隙度分析仪、C101气体渗透测试系统、傅里叶变换红外光谱仪、X射线晶体衍射仪表征电极的形貌特征和化学结构,采用万能材料试验机测试电极的拉伸性能和黏附力,采用电化学工作站检测电极阻抗,通过双导肌肉电模块及多道生理信号采集系统监测肌电图和心电图。【结果】纤维素电纺纳米纤维柔性表皮电极具有有序排列的网状结构和丰富的孔道结构,呈现纤维素Ⅱ晶型结构;当PEDOT:PSS体积分数为20%时,电极的拉伸性能和黏附性最优,即应变为9.8%,杨氏模量0.04 MPa,且对玻璃和猪皮的黏合力(分别为17.8、14.7 N/m)较高;电极在10−2~105 Hz范围内表现出低电极–皮肤电接触阻抗,且能够产生高质量的肌电和心电信号。【结论】本研究以天然纤维素和导电材料为主要构件,制备了一种具有柔性、透气性、自黏附性和低阻抗性能的可穿戴电极。该电极可用于人体电信号监测,为生物相容纤维素基可穿戴电极材料的构建提供了技术支撑。

离子液体中纤维素溶解和再生的微量热

利用等温微量热仪测量1-乙基-3-甲基咪唑醋酸盐离子液体中纤维素溶解和再生微量热,并采用傅里叶红外光谱、X射线衍射分析了再生纤维素结构变化。随着纤维素质量分数增高,溶解焓和再生混合焓均呈先增大后减少趋势。质量分数3%纤维素溶解时,溶解焓值最大(-158.65 J/g);从质量分数1%溶液中纤维素再生时,再生混合焓值最高(-19.24 kJ/g)。溶解焓、再生混合焓与纤维素质量分数之间是非线性关系,说明溶解和再生过程的非理想性。纤维素质量分数显著影响溶解和再生过程热力学特征、再生纤维素氢键模式和晶体结构。

多釜连续溶解加料计算模型用于调控醋酸纤维素浆液固形分浓度

建立了多釜连续溶解加料计算模型,用于测算不同生产条件对醋酸纤维素浆液固形分浓度的影响程度,并进一步通过在实际生产过程中的运行监测,表明在进入溶解釜之前掌握醋酸纤维素和回收浆液等主要原料的关键指标后,通过模型可预测目标浆液固形分浓度的变化,从而通过调整相应参数后有效稳定浆液固形分浓度,确保丝束总旦的稳定。

中石油压裂液技术现状与未来发展

近年来,随着压裂液技术的发展与完善,胍尔胶、合成聚合物、表面活性剂等各种压裂液技术基本成熟并在特定储层或工艺需求的情况下得到应用。阐述了中石油压裂液技术发展及应用现状,认为压裂液主体技术多元化、对高矿度水的适应性以及实现回收再利用是未来一段时期满足压裂液技术需求和控制成本的决定因素;满足低伤害、低成本、高效环保等技术指标仍是未来压裂液发展方向,并对稠化剂速溶及连续混配的技术条件提出新见解;对高温压裂液技术提出新思路;建议尽快建立非常规储层压裂液及其伤害评价方法,以规范和指导压裂液技术发展。