Aqueous Cellulose Solutions Research Articles

PB35 ヒドロキシプロピルセルロース液晶の選択反射を用いた可変色表示デバイスの開発(フォトニクス・光デバイス,ポスター発表,2012年日本液晶学会討論会)

PB35 ヒドロキシプロピルセルロース液晶の選択反射を用いた可変色表示デバイスの開発(フォトニクス・光デバイス,ポスター発表,2012年日本液晶学会討論会)

The viscosity distribution around a rising bubble in shear-thinning non-newtonian fluids

The viscosity distribution of the liquid around a rising bubble in carboxymethyl cellulose (CMC) aqueous solutions was measured experimentally by particle image velocimetry (PIV). The effect of the concentration of CMC solutions on the viscosity distribution around a bubble and the coupling relations between the viscosity field, flow field and shear stress field were also studied. Results indicated that the specific viscosity (non-dimensionalized by η0) decreases with the increase in CMC solution concentration due to a shear thinning effect. Within the experimental range, similar viscosity distributions of liquids around a rising bubble were found: a hollow cylindrical low viscosity region around the bubble wake and a high viscosity region in the central bubble wake.

Sulfonated copolymers with SO3H and COOH groups for the hydrolysis of polysaccharides

The well-defined sulfonated block copolymer poly(acrylic acid)-block-poly(styrene sulfonic acid) (PAA-b-PSSH) and the random copolymer poly(acrylic acid)-random-poly(styrene sulfonic acid) (PAA-r-PSSH) were prepared by direct thermolysis of the precursor copolymers poly(tert-butyl acrylate)-block-poly(neopentyl styrenesulfonate) (PtBA-b-PNSS) and poly(tert-butyl acrylate)-random-poly(neopentyl styrenesulfonate) (PtBA-r-PNSS), which were synthesized by living radical polymerization (MWD < 1.10) catalyzed with CuBr. GPC, EA, 1H NMR and FT-IR spectra were employed to characterize the structure of the synthesized acid polymers. The catalytic performance of the acid polymers was evaluated for the hydrolysis of starch and cellulose in aqueous solution under microwave irradiation. With the same effective acid concentration, the random copolymer PAA-r-PSSH gave the highest glucose yield among the prepared catalysts. It is believed that the good results were caused by the synergic effect of the SO3H and COOH groups in the polymer chain. In addition, microwave irradiation led to better glucose yields in the hydrolysis of polysaccharides than the conventional heating method with acid polymers as catalysts.

Properties of carboxymethyl cellulose aqueous solutions with nanoparticle additives and the related composite films

The rheological properties of carboxymethyl cellulose aqueous solutions containing small amounts of purified montmorillonite and bentonite nanoparticles are studied. The viscosity of mixed solutions decreases after addition of 1 wt % nanoparticles. X-ray diffraction analysis shows that the films contain nanoparticles in the exfoliated state. An examination of the FTIR spectra of composite films suggests a shift in the absorption band due to Si-O groups. This phenomenon may be explained both by a change in the permittivity of the nanoparticle environment and by the formation of hydrogen bonds between Si-O groups and functional groups of cellulose ether. It is shown that the content of the added nanoparticles influences the mechanical characteristics of the films prepared from the systems of interest.

Enthalpies of interaction between cellobiose and the derivatives of cellulose in aqueous solutions

The enthalpy of interaction between cellobiose and sodium carboxymethyl cellulose, methyl cellulose, and 2-hydroxyethyl cellulose in water is determined. The exothermal nature of the interaction between cellulose and cellulose ethers is established. The strongest intermolecular interaction is found between cellobiose and 2-hydroxyethyl cellulose. The results are discussed in the context of the polysaccharide molecular structure.

Hydrodynamic Studies on Three-Phase Combined (Internal &amp; External) Loop Airlift Fluidized Bed Reactor Using Newtonian and non-Newtonian Liquids: Minimum Fluidization Velocity and Liquid Holdup

A novel combined airlift loop fluidized bed reactor was proposed in this work. The internal and external loops were combined and the hydrodynamic parameters like minimum fluidization velocity and liquid holdup were studied for Newtonian and non-Newtonian fluids. Studies were conducted using Newtonian fluids of water, n-butanol, 60% and 80% glycerol and non - Newtonian fluids such as 0.25%, 0.6% and 1.0% Carboxy Methyl Cellulose (CMC) aqueous solutions were employed in the liquid phases. Spheres, Bearl saddle and Raschig ring with different sizes were used as solid phase. The experimental results indicated that the increase in particle size and sphericity increased minimum fluidization velocity whereas increase in superficial gas velocity decreased minimum fluidization velocity. In addition, the liquid holdup increased with increase in particle size and superficial liquid velocity. Furthermore, an increase in superficial gas velocity decreased the liquid holdup for Newtonian and non-Newtonian systems. Two separate correlations were developed to predict the minimum fluidization velocity and liquid holdup based on the experimental results for both Newtonian and non-Newtonian liquids for a wide range of operating conditions. The capability of the proposed correlation for minimum fluidization velocity and liquid holdup was examined and reasonable agreement between predicted and experimental results of Newtonian and non-Newtonian liquids suggested the applicability of the proposed correlations.

Preliminary investigation of factors determining self-organised structures preparation in polymer layers

Factors determining creation of self-organized structures, Bénar–Marangoni cells, during the process of solvent evaporation from the polymer solution and formation of polymer film were studied. Examined parameters were temperature, temperature gradient, rate of drying, height of a liquid layer, area for film preparation, viscosity, molecular weight distribution, etc. A special apparatus, micro condensation drying system, was engineered for this study. As a model system, hydroxyethyl cellulose aqueous solution was used for its excellent film-forming ability and the tendency to self-aggregation. Experimental results, presented in a wide spectrum of self-organized patterns, show the complexity of the problem and the crucial role of molecular weight distribution of the polymer in the fixation of organized structures under highly non-equilibrium conditions.

Synthesis, structural and spectroscopic properties of encapsulated Chlorophyll-a thin film in carboxymethyl cellulose

We report successful retention of the spectroscopic properties of Chlorophyll-a molecules encapsulated in carboxymethyl cellulose acting as an "artificial membrane" material. Films were prepared on indium tin oxide substrates utilizing the spin-coating technique at different concentrations of carboxymethyl cellulose aqueous solution. Results show that the native state of the encapsulated Chlorophyll-a molecules were retained for extended periods of time enhanced further by the optimum concentration effect. Investigations also revealed that the molecules exist in nanocrystal forms with crystal size of 10 nm regardless of the carboxymethyl cellulose concentrations and can be further optimized by varying the spin rates. Chlorophyll-a molecules were found well dispersed in the carboxymethyl cellulose films suggesting the suitability of the gel-like polymer solution as a dispersion agent. It was therefore obvious that the encapsulation of Chlorophyll-a molecules by carboxymethyl cellulose provides prolonged retention of its photoactivity highlighting extended usage when incorporated into future device applications.

Cellulase immobilized mesoporous silica nanocatalysts for efficient cellulose-to-glucose conversion

Two mesoporous silica nanoparticles (MSNs) with different particle size, pore size, and surface area were synthesized and utilized as scaffolds for the immobilization of cellulase, an enzyme that can hydrolyze cellulose in aqueous solution. Two different immobilization methods, i.e., physical adsorption and chemical binding, were used to immobilize cellulase. The reaction conditions, including temperature, time, and the amount of cellulase for cellulosic hydrolysis, were optimized. This study systematically investigates the loading amount, catalytic activity, and stability of cellulase immobilized MSN catalysts. Results show that the cellulase chemically linked to MSN exhibiting carboxyl groups and a large pore size could achieve an effective cellulose-to-glucose conversion exceeding 80% yield and excellent stability.

Prediction of gas holdup in a combined loop air lift fluidized bed reactor using Newtonian and non-Newtonian liquids

Many experiments have been conducted to study the hydrodynamic characteristics of column reactors and loop reactors. In this present work a novel combined loop airlift fluidized bed reactor was developed to study, the effect of superficial gas and liquid velocities, particle diameter, fluid properties on gas holdup by using Newtonian and non-Newtonian liquids. Compressed air was used as gas phase. Water, 5% n-butanol, various concentrations of glycerol (60 % and 80 %) were used as Newtonian liquids, different concentrations of Carboxy Methyl Cellulose (0.25 %, 0.6 % and 1.0 %) aqueous solutions were used as non-Newtonian liquids. Different sizes of Spheres, Bearl saddles and Raschig rings were used as solid phases. From the experimental results it was found that the increase in superficial gas velocity increases the gas holdup, but it decreases with increase in superficial liquid velocity and viscosity of liquids. Based on the experimental results a correlation was developed to predict the gas holdup for Newtonian and non-Newtonian liquids for a wide range of operating conditions at a homogeneous flow regime where the superficial gas velocity is approximately less than 5 cm/s.

Thermal conductivity of non-Newtonian nanofluids: Experimental data and modeling using neural network

Three different types of nanofluids were prepared by dispersing γ-Al2O3, TiO2 and CuO nanoparticles in a 0.5wt% of carboxymethyl cellulose (CMC) aqueous solution. Thermal conductivity of the base fluid and nanofluids with various nanoparticle loadings at different temperatures were measured experimentally. Results show that the thermal conductivity of nanofluids is higher than the one of the base fluid and the increase in the thermal conductivity varies exponentially with the nanoparticle concentration. In addition to increase with the nanoparticle concentration, the thermal conductivity of nanofluids increases with the temperature. Neural network models were proposed to represent the thermal conductivity as a function of the temperature, nanoparticle concentration and the thermal conductivity of the nanoparticles. These models were in good agreement with the experimental data. On the other hand, the Hamilton Crosser model was only satisfactory for low nanoparticle concentrations.

Synthesis and optical characterization of ZnS–sodium carboxymethyl cellulose nanocomposite films

In this work, the synthesis and characterization of ZnS–sodium carboxymethyl cellulose nanocomposite films were studied. The film was prepared by casting after the in situ precipitation of ZnS in sodium carboxymethyl cellulose (NaCMC) aqueous solution. The in situ method avoids nanoparticles aggregation and improves its dispersion. The resulting nanocomposite was characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The results showed that ZnS nanoparticles with a blende structure and a particle size in the range of few nanometers are well dispersed in the sodium carboxymethyl cellulose films. Optical properties were analyzed by using UV–vis spectroscopy and photoluminescence spectroscopy (PL). The resulting nanocomposite films showed optical transmission between 50% and 90% influenced by the amount of ZnS nanocrystals into the nanocomposite films. The PL spectra of the nanocomposite films exhibits a broad visible emission band centered at 445nm under UV light excitation (λ=320nm). These luminescent films might have a potential application in security paper by using an optical signature.

ESR study on radiation-induced radicals in carboxymethyl cellulose aqueous solution

Carboxymethyl cellulose (CMC) at highly concentrated aqueous solution undergoes radiation crosslinking reaction by ionizing irradiation. It is assumed that this radiation-induced reaction takes place by the indirect effect of water radiolysis, especially through the OH radical. However, the reaction mechanism is not well known. In this topic, ESR spectra of CMC radicals formed by reaction with OH radicals were measured directly in aqueous solution to identify the initially formed radical site. The ESR spectra were observed successfully and were interpreted as the overlapping of two spectra; a Triplet×Doublet spectrum and a Doublet spectrum. Each spectrum was assigned to radicals located on carboxymethyl groups linked to C6 and C2/C3.

Addition effects of imidazolium salts on mesophase structure and optical properties of concentrated hydroxypropyl cellulose aqueous solutions

Addition effects of N-alkyl-substituted methylimidazolium salts ([CnMim][X]) on the mesophase structure and lower critical solution temperature (LCST)-type phase-separation behavior of concentrated hydroxypropyl cellulose (HPC) aqueous solutions were investigated mainly by spectrophotometry. In the cholesteric mesophase formation, at concentrations of more than 50 wt% HPC, helical pitch (P) was confirmed to shift upward according to the chaotropic strength of X–, for example, in a manner satisfying the order of Cl−<Br−<NO3−<I−. Organocations generally elevated P relative to the nonionic reference, the effectiveness being pronounced in the order of [C2Mim]+<[C4Mim]+<[C6Mim]+. With regard to LCST behavior, imidazolium additives raised the cloud point (Tc) in the isotropic solutions of ⩽40 wt% HPC, whereas the Tc value of mesomorphic solutions was prone to be lowered by the addition. Discussion of these observations took into consideration the differences in the N-alkyl structure and amphiphilic nature between cationic imidazolium varieties, as well as the difference in the chaotropic strength between the counter anions. It was also exemplified preliminarily that this kind of salt-containing lyotropic system of HPC exercised an electro-optical function when coupled with an electric circuit. Addition effects of a series of N-alkyl-substituted methylimidazolium salts ([CnMim][X]) on the mesophase structure and LCST-type phase-separation behavior, and the ensuing optical properties of concentrated hydroxypropyl cellulose (HPC) aqueous solutions, were investigated by spectrophotometry and complementary X-ray diffractometry. Salted HPC solutions exhibited distinct shifts in both the cholesteric pitch and the cloud point, relative to the nonionic reference. Discussion of the observations took into consideration the differences in the N-alkyl structure and amphiphilic nature between the imidazolium varieties, as well as the difference in a socalled chaotropic strength between the anions used.

Aggregation and sedimentation stability of microcrystalline cellulose suspensions in aqueous aluminum nitrate solutions

The aggregation and sedimentation stability of dilute suspensions of microcrystalline cellulose in aqueous solutions of Al(NO3)3(2 × 10−5–2 × 10−3 mol/l) is studied by the photometric method at pH 2–11. It is found that, in the absence of Al(NO3)3, microcrystalline cellulose suspensions are stable with respect to aggregation throughout the pH range in question. The addition of Al(NO3)3 induces the coagulation and accelerates the sedimentation of microcrystalline cellulose aggregates. At all concentrations of Al(NO3)3, the maximum loss in stability is observed at pH 7–9.

Aggregation and gelation in hydroxypropylmethyl cellulose aqueous solutions

In this work we present an analysis of the thermal behavior of hydroxypropylmethyl cellulose aqueous solutions, from room temperature to higher temperatures, above gelation. We focus on significant aspects, essentially overlooked in previous work, such as the correlation between polymer hydrophobicity and rheological behavior, and the shear effect on thermal gelation. Micropolarity and aggregation of the polymer chains were monitored by both UV/vis and fluorescence spectroscopic techniques, along with polarized light microscopy. Gel formation upon heating was investigated using rheological experiments, with both large strain (rotational) tests at different shear rates and small strain (oscillatory) tests. The present observations allow us to compose a picture of the evolution of the system upon heating: firstly, polymer reptation increases due to thermal motion, which leads to a weaker network. Secondly, above 55 °C, the polymer chains become more hydrophobic and polymer clusters start to form. Finally, the number of physical crosslinks between polymer clusters and the respective lifetimes increase and a three-dimensional network is formed. This network is drastically affected if higher shear rates, at non-Newtonian regimes, are applied to the system.

Microviscosity of hydrophobically modified hydroxyethyl cellulose aqueous solutions

The microviscosity of hydrophobically modified hydroxyethyl cellulose (HMHEC) aqueous solutions is experimentally determined by conductometry with added ions as probe. Compared to its bulk viscosity, the microviscosity of HMHEC solution could be lower by four orders of magnitude. Since the electric conductivity reduction of added NaCl is almost the same for HMHEC and its unmodified counterpart at an equal weight concentration, one can conclude that the hydrophobic modification for the polymer hardly has any effect on the solution's microviscosity.

Nonlinear rheology of aqueous solutions of hydrophobically modified hydroxyethyl cellulose with nonionic surfactant

Shear thickening and strain hardening behavior of hydrophobically modified hydroxyethyl cellulose (HMHEC) aqueous solutions was experimentally examined. We focused on the effects of polymer concentration, temperature, and addition of nonionic surfactant. It is found that HMHEC shows stronger shear thickening at intermediate shear rates in a certain concentration range. In this range, the zero-shear viscosity scales with polymer concentration as η 0 ∼ c 5.7 , showing a stronger concentration dependence than for more concentrated solutions. The critical shear stress for complete disruption of the transient network follows τ c ∼ c 1.62 in the concentrated regime. Dynamic tests of the transient network on addition of surfactants show that the enhanced zero-shear viscosity is due to an increase in network junction strength, rather than their number, which in fact decreases. The reduction in the junction number could partly explain the weak variation of strain hardening extent for low surfactant concentrations, because of longer and looser bridging chain segments, and hence lesser nonlinear chain stretching.

Solid State Foaming and Free-Forming of Closed Pore Utilizing the Superplasticity of Zirconia Ceramics

The purpose of this study is to make a superplasticity ceramic foam with several isolated closed pores. Three mol percent of yttria stabilized zirconia (3YSZ) was used as foam matrix and β -SiC as foam agent. Two kinds of powder slurries based on methyl cellulose aqueous solution were first prepared. Using the 3YSZ slurry, green sheet was fabricated using a glass bar. After dried, patterning of SiC slurry was conducted on the 3YSZ sheet through a copper mask. Three patterned sheets were cut and buried in a 3YSZ powder compacts. Through the heat treatment at the sintering temperature, a ceramic foam containing several isolated closed pores derived from the SiC pattern was successfully fabricated.

Selective Reflection of Hydroxypropyl Cellulose Prepared with Autoclave

A hydroxypropyl cellulose (HPC) aqueous solution has been attracting attention as an electrically color-changeable reflector. The purpose of this study is to shorten the preparation time of HPC aqueous solution. By the conventional method, preparation takes more than three weeks, because the HPC solution has a high viscosity. We provide a novel preparation method for HPC aqueous solution using an autoclave. The preparation duration was shortened to only three days. The uniformity of the selective reflection and reproducibility of the cell were also evaluated in this study.