Rheological properties of concentrated solutions of agarose in ionic liquid

The rheological properties of agarose solutions were examined under the effect of entanglement coupling between agarose chains. Agarose solutions were prepared by using an ionic liquid 1‐butyl‐3‐methylimidazolium chloride as a solvent. The concentration of agarose was varied from 1.1 × 10¹–2.1 × 10² kg m^?3. The master curves of the angular frequency (ω) dependence of the storage modulus (G′) and the loss modulus (G″) showed a rubbery region in the middle ω region and a flow region at low ω region, respectively. The molecular weight between entanglements (M_e) for agarose was calculated from the plateau modulus. Moreover, M_e for agarose melt was determined to be 2.3 × 10³ from the concentration dependence curve of M_e. By using well‐known empirical relations in polymer rheology, information on molecular characteristics of sample agarose was derived. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Rheological properties of concentrated cellulose solutions in N-methylmorpholine-N-oxide

Conclusions -- Rheological properties of concentrated solutions of cellulose in N-mcthylmorpholine-N-oxide on varying the concentration of cellulose in the solution from 10 to 28% by wt. have been studied.-- It has been found that on increasing the cellulose content of the solution, the viscoelastic properties of the solution qualitatively change.-- In spinning highly concentrated solutions (cellulose content greater than 20%) an abrupt impairment takes place in stability of jet formation; this is connected with a change in supermolecular structure and elastic properties of the solution.Translated from Khimicheskie Volokna, No. 6, pp. 32–34, November–December, 1990.     

Rheological properties of high concentrations of carboxymethyl cellulose solutions

The study was concerned with measurements of steady‐state parameters, the transient shear stress response, and the yield stress of carboxymethyl cellulose (CMC) solutions at high concentrations. Tests also included thixotropic and viscoelastic behavior and dynamic responses. The concentrations ranged by weight from 5 to 8% of CMC. The steady‐state shear flow showed that at higher shear rates the viscosities of CMC solutions tend to be less dependent on the concentration. The solutions showed rheopectic behavior for very small shear rates. No yield stress was detected. Measurements recorded the thixotropic behavior. At higher stress values, nonlinear viscoelastic effects were detected. Dynamic viscosities measured in a dynamic test were higher than were the shear viscosities at the same concentrations. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1787–1801, 2001     

Unperturbed molecular dimensions and the theta temperature of dextran in dimethylsulfoxide (DMSO) solutions

Summary The unperturbed molecular dimensions of dextran samples have been determined in dimethylsulfoxide (DMSO) solutions from intrinsic viscosity measurements at different temperatures. The unperturbed dimension parameter, K_o, has been calculated from extrapolation methods.The unperturbed root-mean-square end-to-end distance, <r²>_o ^1/2, found for the polymer samples in DMSO solutions, indicate that the polymer coils are contracted. This distance varies from 3.25 × 10⁻⁷ cm to 2.94 × 10⁻⁷ cm for the sample T 40 and from 8.28 × 10⁻⁷ cm to 7.48 × 10⁻⁷ cm for the sample T 500, in the chosen solvent as the temperature is raised from 25°C to 45°C. In the system of dextran/DMSO, the long-range interaction parameter, B, was also determined and a significant decrease is observed between 25°–45°C. The theta temperatures, Θ, were obtained as Θ= 327.25 K, Θ= 327.41 K and Θ= 323.38 K from the temperature dependence of the interaction parameter in Kurata-Stockmayer-Fixman, Berry and Inagaki-Suzuki-Kurata equations, respectively. Received: 19 January 1998/Revised version: 9 June 1998/Accepted: 10 June 1998     

Rheological properties of cellulose/chitin xanthate blend solutions and properties of the prepared fibers

The focus of this article is the rheological properties of cellulose xanthate, chitin xanthate, and their blend solutions with cellulose/chitin blend weight ratios of 9.5 : 0.5, 9 : 1, 8 : 2, and 5 : 5 (mostly 9 : 1 blend solutions). The preparation and properties of fibers from 9 : 1 blend solutions and cellulose xanthate solutions are also discussed. The non‐Newtonian index of the investigated solutions was found to vary in the following order: chitin < cellulose < 9.5 : 0.5 blend < 9 : 1 blend < 8 : 2 blend < 5 : 5 blend. Showing a tendency contrary to that of the non‐Newtonian index, the structure viscosity index varies in the following order: chitin > cellulose > 9.5 : 0.5 blend > 9 : 1 blend > 8 : 2 blend > 5 : 5 blend. For 5–9 wt % 9 : 1 blend solutions, increasing the solution temperature aids the improvement of the fluidity of 9 : 1 blend solutions in the temperature range of 10–40°C. The zero shear viscosity decreases in an index manner with the solution temperature increasing. The 7–8 wt % 9 : 1 blend solutions have good filtering and rheological properties and are ideal for spinning fibers. The mechanical properties of blend fibers spun from 7% 9 : 1 blend solutions are lower than those of pure cellulose and are much higher than those of Crabyon fiber, and they still reach the national criteria and fit the need for further processing. This proves that the viscose method which we have developed here is an efficient way of preparing cellulose/chitin blend fibers with satisfactory mechanical properties and processing properties. Scanning electron microscopy photographs show that the surface of 9 : 1 blend fibers is coarser than that of pure cellulose fibers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Swelling behaviors of natural cellulose in ionic liquid aqueous solutions

In the study, a series of methylimidazolium ionic liquids were prepared, including five acidic and seven neutral ionic liquids; and the effects of these ionic liquids on swelling behavior of bagasse cellulose were investigated. The focus of this work is to investigate the relationship between the properties of ionic liquids and the swelling capacity. The swelling absorbency for cellulose in the acidic ionic liquid aqueous solutions was less than in distilled water. It was found that the partial hydrolysis on cellulose surface occurred along with swelling simultaneously. In neutral ionic liquid aqueous solutions, the nonlinearity of swelling ability with the alkyl chain length was discovered. It could be attributed to the dual role of hydrophobic interactions and steric effects provided by cations. Furthermore, small polarizable anions also contribute to the swelling of cellulose to some extent. The properties of treated cellulose were also investigated and compared with the native fibers by scanning electron microscopy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40199.     

Rheological properties of spinning solutions for cellulose acetate ultrafiltration membranes

Addition of ethyl alcohol in the amount of 5 to 25 wt. % significantly reduces the viscosity of secondary cellulose acetate (SCA)—acetone—water spinning solutions. The effective viscosity of the spinning solutions decreases significantly when the shear stress changes. SCA membranes made from solutions with lower viscosity have higher permeability both for water and for cheese whey. The data obtained can be used to vary the performance properties of ultrafiltration membranes within wide limits. __________ Translated from Khimicheskie Volokna, No. 1, pp. 15–17, January–February, 2007.     

聚丙烯腈/离子液体溶液流变性能的研究

采用应力流变仪对聚丙烯腈/1-丁基-3-甲基咪唑氯化物(PAN/[BMIM]Cl)溶液体系的稳态和动态流变性能进行了研究,讨论了PAN相对分子质量(Mη)对溶液稳态和动态流变性能的影响。结果表明:PAN/[BMIM]Cl溶液在低剪切速率区表现出牛顿流体特征,在高剪切速率区随着剪切速率的增大粘度降低,表现为切力变稀流体;溶液的粘度大于常规溶剂体系,随着PAN的Mη增大,PAN/[BMIM]Cl溶液表观粘度明显增大,非牛顿指数减小,粘流活化能增大;溶液的损耗模量和储能模量越大,溶液更容易表现出弹性效应。     

氯盐离子液体水溶液的物理化学性质

离子液体是一类新型表面活性剂,研究离子液体+水体系的物性具有重要的意义。为此,本文测定了不同浓度和温度下［Bemim］［Cl］（氯化-1-甲基-3-苄基咪唑）,［C_nmim］［Cl］（氯化-1-甲基-3-烷基咪唑, n=4,14,16）,［BeiQu］［Cl］（氯化-N-苄基异喹啉）,［C_miQu］［Cl］（氯化-N-烷基异喹啉, m=4,8）等氯盐离子液体水溶液的密度、动力黏度、表面张力等物化性质。氯盐离子液体水溶液密度的变化趋势为咪唑类>异喹啉类。离子液体水溶液的黏度随着温度的升高而减小,随着浓度的升高而升高。在等温条件下,阳离子取代基相同时,离子液体水溶液的表面张力的变化趋势为咪唑类<异喹啉类。     

Rheological studies of cellulose derivatives solutions

The rheological behavior of solutions of cellulose derivatives, acetate, and hydroxypropyl was studied as a function of different parameters; molecular weight, concentration,…, at T = 25°C in the vicinity of the liquid crystal phase transition. A variation of the strain rate sensitivity parameter with concentration is found. A degradation of the solution in trifluoroacetic acid is demonstrated.     

Rheological properties of collagen/hydroxypropyl methylcellulose (COL/HPMC) blended solutions

Collagen/HPMC blends with different HPMC content (HC) were investigated by dynamic responses, creep recovery, thixotropy, and morphological observation. Storage modulus, loss modulus, complex viscosity, and activation energy decreased with the increased HC, while the flow behavior index increased with the increased HC and the dynamic denaturation temperature reached the maximum as HC increased to 50%, indicating that the flowability and thermal stability of collagen solution were improved by the addition of HPMC. However, the blends with higher HC tended to have a relatively lower recovery capacity, and the hysteresis loop areas of the blends were lower than that of collagen (especially when HC > 50%). Additionally, the morphology of collagen/HPMC was examined by both of atomic force microscopy and scanning electron microscopy. By combining with these results, it seemed that the rheological and structural properties of collagen/HPMC were related to the hydrogen‐bond interaction and compatibility between collagen and HPMC molecules. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40042.     

Rheological properties of carboxymethyl cellulose

This work is a complete and comprehensive study of the rheological properties of carboxymethyl cellulose (CMC) solutions. The study was carried out using the computer controlled RheoStress RS100 system of Haake. CMC concentration in the test solutions ranged by weight from 1 to 5%. This range was sufficiently wide to reveal the nearly Newtonian behavior at the lower end of concentrations, and the definitely pseudoplastic, thixotropic, and viscoelastic behaviors of CMC solutions at the higher end of concentrations. The scope of the study included measurements of steady-state parameters, transient shear stress response, and yield stress. In addition, the thixotropic, creep recovery, and dynamic responses of solutions with high concentrations were measured. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 289–301, 1997     

Rheological properties and microstructures of cellulose acetate phthalate/hydroxypropyl cellulose blends

Cellulose acetate phthalate (CAP)/hydroxypropyl cellulose (HPC) blends were investigated by means of attenuated total reflection‐Fourier transform infrared spectroscopy, thermogravimetry/differential thermal analysis, shear viscosity, oscillatory shear tests, and atomic force microscopy (AFM). Effect of solution concentrations in 2‐methoxyethanol, blend compositions, and shear rate on the rheological functions reflects the mobility of the chain segments or their orientation—with thinning behavior in the shear field. Specific interactions, such as the hydrogen bonds between polymer components and 2‐methoxyethanol used in casting solutions of films, influence the resulting morphology. Supernodular aggregates with different intensities and dimensions, which involve the coexistence of an isotropic and an anisotropic phase, typical for lyotropic cellulosic derivative liquid crystals at low concentrations, are evidenced by AFM images. This study is useful for applications of CAP/HPC blends in pharmaceutical domains.POLYM. COMPOS., 33:2072–2083, 2012. © 2012 Society of Plastics Engineers     

Rheological properties of poly(ethylene oxide) aqueous solutions

This article describes the rheological properties of certain poly(ethylene oxide)s dissolved in water-based solvents. The experimental results show that the rheological properties in aqueous solutions are significantly affected by the solvent properties, which have been changed by the use of ethanol–water mixtures and electrolyte solutions and by the variation of the ambient pressure and temperature. The variation of the temperature and pressure is seen to change the polymer chain configuration and also the interactions of polymer segments with the solvent molecules. This gives rise to distinctive and apparently unusual rheological properties for these systems with the variation of the ambient temperature and pressure. The study generally illustrates that the rheology of these systems are, to a large degree, influenced by the hydrogen bonding in the solvent and between the solvent as well as the polymer. At a first-order level, the increase of the pressure and the temperature and also the addition of electrolytes, and the inclusion of an aqueous diluent, produce comparable effects. In essence, these changes seem to disrupt the hydrogen bonding structure in the solutions and, hence, the solvent quality in a comparable fashion. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 419–429, 1998     

Rheological properties of corona modified cellulose/polyethylene composites

The rheological behavior of wood fiber/polyethylene composites made of corona treated constituents was investigated. Corona treatment of one or both of the constituents resulted in decreased melt viscosities relative to compounds containing untreated materials. The reduction of melt viscosity may originate from low molecular weight moieties formed on the surfaces of both polyethylene and cellulose during corona treatment. These may act as lubricants at interfaces. Also it was found that the corona treatment of fibers leads to higher packing volumes; this may result from a reduction in fiber length when treated fibers are processed under high shear conditions. As a result these fibers perturb the normal flow pattern in the melt to a lesser degree than the longer fibers of untreated cellulose.     

Rheological properties of aqueous polyacrylamide/NaCl solutions

Rheological properties of aqueous polyacrylamide‐sodium chloride solutions are studied using RheoStress RS100. Polyacrylamide concentration was varied from 0.25 to 1.0% by weight, whereas sodium chloride ranged from 0.0 to 10 g L⁻¹. This range of concentrations is suitable to study many of the polyacrylamide‐sodium chloride rheological properties. Steady flow parameters, yield stress, thixotropic behavior, creep recovery, and dynamic tests are covered in this study. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1905–1912, 1999     

Rheological properties of hydrolyzed polyacrylonitrile-grafted cellulose

The rheological properties of aqueous dispersions of hydrolyzed polyacrylonitrile-grafted cellulose (H-CPAN) have been investigated. The experimental results are consistent with the idea that the elementary particle is a rigid cellulose protofibril stabilized in suspension by associated polyelectrolyte side chains (polyacrylamide–polyacrylic acid copolymer grafts). The behavior of intrinsic viscosity with electrolyte concentration, the concentration depependence and shear dependence of the viscosity and of the steady-state and dynamic shear moduli are qualitatively explained on this basis.     

离子液体中纤维素的均相改性及其产物性能

卤代基团比羟基具有更高的反应活性,因此将含有卤素基团的有机化合物引入到纤维素骨架上可以提高其反应活性,为其后续接枝改性提供更广的应用范围。以氯乙酰氯为酯化剂,离子液体1-丁基-3-甲基咪唑氯盐（［Bmim］Cl）为反应介质,在不加任何催化剂的情况下,直接进行纤维素的均相酯化改性。着重探讨了反应温度、反应时间、酯化剂用量等因素对反应的影响。利用红外光谱（IR）以及核磁共振（NMR）对产物结构进行表征,并研究改性后纤维素在溶剂中的溶解性能。结果表明,离子液体中纤维素的均相酯化改性的最佳工艺条件为：纤维素葡萄糖单元与氯乙酰氯的摩尔比为1∶3,反应温度为常温,反应时间为2 h。此时,改性纤维素取代度为1.36。此外,改性后,纤维素酯易溶于丙酮、二甲基亚砜、四氢呋喃等有机溶剂。