Viscosity Of Cellulose Research Articles

Effect of a magnetic field on the rheological properties of cellulose ether solutions

Application of a magnetic field is shown to be accompanied by an increase in the viscosity of hydroxyethyl cellulose and ethyl cellulose solutions and an additional assembly of macromolecules, as is evident from a gain in the radii of light-scattering particles. The concentration dependences of supramolecular-particle radius and solution viscosity in the presence of a magnetic field are described by curves with maxima.

Improved refining properties of pulps pretreated with ionic liquids under mild conditions

Imidazolium-based ionic liquids (ILs), including 1-butyl-3-methylimidazolium chloride (BmimCl) and 1-allyl-3-methylimidazolium chloride (AmimCl), were used to improve the refining properties of pulps under mild conditions. Results showed that the macro appearance of pulps was virtually unchanged after pretreatment with ILs under mild conditions. In addition, chemical pulps pretreated with ILs are more suitable for pretreatment than chemimechanical pulps. Pretreatment with ILs facilitates the refining process by destroying hydrogen bonds, which exist extensively in fiber. At the same refining energy input, the Canada standard freeness (CSF) of refined pulp decreased with improved fiber quality. At identical CSF values, the energy consumed during refining significantly decreased because ILs pretreatment facilitated swelling and fibrillation. The viscosity of cellulose changed slightly after IL pretreatment. However, the crystallinity index and fines content decreased, and the micro appearance of the fiber surface changed. BmimCl has a stronger swelling influence on pulp than AmimCl under optimal conditions.

Characterization of thermal and rheological properties of zidovidine, lamivudine and plasticizer blends with ethyl cellulose to assess their suitability for hot melt extrusion

The influence of antiretroviral drugs and plasticizers on the rheological and thermal characteristics of ethyl cellulose formulations intended for hot melt extrusion has been investigated. Antiretroviral drugs used were zidovudine and lamivudine, whilst plasticizers included triethylcitrate (TEC) and polyethylene glycol (PEG-6000). Physical mixtures containing ethyl cellulose with varying concentrations of drugs and plasticizers were characterized using differential scanning calorimetry (DSC) and parallel plate oscillatory rheometry. The viscosity of physical mixtures containing both drugs was lower than observed for pure ethyl cellulose, indicating that the drugs had a plasticizing effect. This was confirmed by lowering of the glass transition temperature (Tg) of ethyl cellulose. At the highest loading of 40% by weight, lamivudine appeared to become saturated within the polymer, causing an increase in viscosity and showing evidence of recrystallization upon cooling. Both TEC and PEG-6000 were found to lower the Tg of ethyl cellulose, although PEG-6000 recrystallized upon cooling which makes it unsuitable for use in the proposed controlled release formulations. Both plasticizers were also shown to reduce the viscosity of ethyl cellulose, more significantly so for TEC. The results indicate that ethyl cellulose formulations containing up to 40% by weight of zidovudine, not more than 30% by weight of lamivudine, with 5–10% by weight of TEC as the plasticizer are suitable for processing by hot melt extrusion.

Synthesis and characterization of carboxymethyl cellulose powder and films from Mimosa pigra

AbstractMimosa pigra peel was sun‐dried for 2 days and then ground before being boiled with 30%w/v sodium hydroxide (NaOH) at 100°C for 3 h, washed and then dried at 55°C to constant weight. The cellulose was then synthesized using different NaOH concentrations and monochloroacetic acid (MCA) in isopropyl alcohol (IPA). Effects of various NaOH concentrations on degree of substitution (DS), viscosity and thermal of carboxymethyl cellulose from Mimosa pigra peel (CMCm) were investigated. The increasing of NaOH concentration resulted in increasing DS and viscosity. However, viscosity of CMCm decreased as temperature increased. Thermal properties were studied using differential scanning calorimetry (DSC). The melting point of the samples decreased as %NaOH increased. The effects of various NaOH concentrations in CMCm synthesis on the mechanical properties and water vapor permeability (WVP) of the CMCm films were investigated as well. With increasing NaOH concentrations (30–50%) were also found to result in improved mechanical properties. However, when the level of NaOH concentration was 60%, the mechanical properties of the CMC films decreased. This result indicates that the highest mechanical properties were found for 50% NaOH‐synthesized CMCm films. The WVP of the CMCm films increased as %NaOH increased. In addition, the CMCm films were tested to determine the effect of glycerol as a plasticizer on the mechanical properties. Increasing the amount of glycerol showed an increase in elongation at break but also led to a decrease in tensile strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Formulation and Evaluation of Press Coated Tablets for Pulsatile Drug Delivery Using Hydrophilic and Hydrophobic Polymers

The aim of present investigation was to develop press coated tablet for pulsatile drug delivery of ketoprofen using hydrophilic and hydrophobic polymers. The drug delivery system was designed to deliver the drug at such a time when it could be most needful to patient of rheumatoid arthritis. The press coated tablets containing ketoprofen in the inner core was formulated with an outer shell by different weight ratio of hydrophobic polymer (micronized ethyl cellulose powder) and hydrophilic polymers (glycinemax husk or sodium alginate). The release profile of press coated tablet exhibited a lag time followed by burst release, in which outer shell ruptured into two halves. Authors also investigated factors influencing on lag time such as particle size and viscosity of ethyl cellulose, outer coating weight and paddle rpm. The surface morphology of the tablet was examined by a scanning electron microscopy. Differential scanning calorimeter and Fourier transformed infrared spectroscopy study showed compatibility between ketoprofen and coating material.

Carbohydrate degradation during softwood kraft cooking – influence on cellulose viscosity, carbohydrate composition and hexenuronic acid content

Article Carbohydrate degradation during softwood kraft cooking – influence on cellulose viscosity, carbohydrate composition and hexenuronic acid content was published on August 1, 2008 in the journal Nordic Pulp & Paper Research Journal (volume 23, issue 3).

Physicochemical Properties of Cellulose Selectively Oxidized with the 2,2,6,6‐Tetramethyl‐1‐Piperidinyl Oxoammonium Ion

This study examined the characteristics of the oxidation reaction on the primary alcohol groups in cellulose involving the 2,2,6,6-tetramethyl-1-piperidinyl oxoammonium ion (TEMPO) and determined the optimum conditions for the preparation of oxidized cellulose (OC). The applicability of OC in polysaccharide systems was also investigated. The effects of TEMPO, sodium bromide (NaBr), and temperature on the oxidation reaction time, yield, and selectivity for primary alcohol groups were examined using response surface methodology (RSM). The reaction time decreased with increases in the temperature and the levels of TEMPO and NaBr. The yield increased with the level of NaBr and decreased as the temperature increased. Selectivity increased with the temperature and decreased as the levels of TEMPO and NaBr increased. The optimum levels of TEMPO and NaBr and the optimum temperature for the production of OC were determined as 0.3 mM/100 mM anhydroglucose unit (AGU), 50 mM/100 mM AGU, and 25 degrees C, respectively. The water and oil binding capacity and viscosity of cellulose increased with oxidation. Wheat starch containing OC exhibited a decreased initial pasting temperature and setback, but increased peak viscosity, gelatinization, and retrogradation enthalpy (DeltaH). The hardness of the wheat starch gel decreased significantly upon the addition of OC.

Dilute solution properties of cellulose in LiOH/urea aqueous system

AbstractCellulose was dissolved rapidly in 4.6 wt % LiOH/15 wt % urea aqueous solution and precooled to –10 °C to create a colorless transparent solution. 13C‐NMR spectrum proved that it is a direct solvent for cellulose rather than a derivative aqueous solution system. The result from transmission electron microscope showed a good dispersion of the cellulose molecules in the dilute solution at molecular level. Weight‐average molecular weight (Mw), root mean square radius of gyration (〈s2〉z1/2), and intrinsic viscosity ([η]) of cellulose in LiOH/urea aqueous solution were examined with laser light scattering and viscometry. The Mark–Houwink equation for cellulose in 4.6 wt % LiOH/15 wt % urea aqueous solution was established to be [η] = 3.72 × 10−2 M in the Mw region from 2.7 × 104 to 4.12 × 105. The persistence length (q), molar mass per unit contour length (ML), and characteristic ratio (C∞) of cellulose in the dilute solution were given as 6.1 nm, 358 nm−1, and 20.8, respectively. The experimental data of the molecular parameters of cellulose agreed with the Yamakawa–Fujii theory of the worm‐like chain, indicating that the LiOH/urea aqueous solution was a desirable solvent system of cellulose. The results revealed that the cellulose exists as semistiff‐chains in the LiOH/urea aqueous solution. The cellulose solution was stable during measurement and storage stage. This work provided a new colorless, easy‐to‐prepare, and nontoxic solvent system that can be used with facilities to investigate the chain conformation and molecular weight of cellulose. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3093–3101, 2006

The primate amygdala: Neuronal representations of the viscosity, fat texture, temperature, grittiness and taste of foods

The primate amygdala is implicated in the control of behavioral responses to foods and in stimulus-reinforcement learning, but only its taste representation of oral stimuli has been investigated previously. Of 1416 macaque amygdala neurons recorded, 44 (3.1%) responded to oral stimuli. Of the 44 orally responsive neurons, 17 (39%) represent the viscosity of oral stimuli, tested using carboxymethyl-cellulose in the range 1–10,000 cP. Two neurons (5%) responded to fat in the mouth by encoding its texture (shown by the responses of these neurons to a range of fats, and also to non-fat oils such as silicone oil ((Si(CH 3) 2O) n) and mineral oil (pure hydrocarbon), but no or small responses to the cellulose viscosity series or to the fatty acids linoleic acid and lauric acid). Of the 44 neurons, three (7%) responded to gritty texture (produced by microspheres suspended in cellulose). Eighteen neurons (41%) responded to the temperature of liquid in the mouth. Some amygdala neurons responded to capsaicin, and some to fatty acids (but not to fats in the mouth). Some amygdala neurons respond to taste, texture and temperature unimodally, but others combine these inputs. These results provide fundamental evidence about the information channels used to represent the texture and flavor of food in a part of the brain important in appetitive responses to food and in learning associations to reinforcing oral stimuli, and are relevant to understanding the physiological and pathophysiological processes related to food intake, food selection, and the effects of variety of food texture in combination with taste and other inputs on food intake.

Flow properties of sugar beet pulp cellulose and intrinsic viscosity–molecular weight relationship

Cellulose was extracted with 5, 10, 15% NaOH at 25, 35, 45 °C for 10, 16, 22 h from defatted, protein, pectin and hemicellulose free, delignified sugar beet pulp. Extraction with 10% NaOH at 35 °C for 22 h gave the highest yield of the removal of substances with the exception of cellulose. The effects of temperature and concentration on the viscosity of sugar beet pulp cellulose solutions were examined at different temperatures and concentration levels. Twenty-eight different model equations that describe the combined effects of temperature and concentration on the viscosity were derived. Theoretical models describing the temperature and concentration dependence of viscosity were fitted to the experimental data and the model parameters in equations were determined by multiple regression analysis of the experimental data in the temperature range 10–60 °C and in the concentration range 0.5–10 kg/m 3. The viscosity of cellulose from sugar beet pulp can be predicted by the single equation: ln η=−2.8C 0.0186+1031C 0.025/T+2654 exp(0.1896C)/T 2. The average molecular weight was measured by light scattering technique. Intrinsic viscosities and molecular weights of cellulose obtained at different extraction conditions ranged between 0.347–0.0836 m 3/kg and 303,200–893,500 kg/kg mol, respectively. The molecular weight dependence of the intrinsic viscosity of the sugar beet pulp cellulose solutions was expressed by Mark-Houwink-Sakurada equation. The intrinsic viscosity–molecular weight relationship was found as η i =2.313×10 −6( M w,ave) 0.7665.

The Online Measurement of Lyocell Fibers and Investigation of Elongational Viscosity of Cellulose N ‐methylmorpholine‐ N ‐oxide Monohydrate Solutions

In this paper, the development of diameter and surface temperature of lyocell fibers was measured online. The diameter and tensile force on the spin line in the coagulation bath were traced. The velocity, velocity gradient and the tensile stress profiles development of the fibers in the air grap were studied. The apparent elongantional viscosity of cellulose N-methylmorpholine-N-oxide monohydrate (NMMO-MH) solutions was studied by steady-state melt spinning theory. The decrease of the fiber diameter was mainly taking place near the spinneret, and the decrease of the diameter became more dramatic with increasing taking-up speed. The surface temperature of the fibers was also dropping faster with increasing takin-up speed for the heat transfert coefficient increased. The diameter of the Lyocell fibers almost did not change before and after it entered the coagualtion bath. The tensile force on the spin line increase with increasing taking-up speed and coagulation bath length. The velocity and the tensile strees increase slowly near the spinneret, and then accelerate. The apparent elongational viscosity of cellulose NMMO-MH solutions decreases with increasing temperature at the same elongation rate and decreases with increasing elongation rate at the same temperature. The fiber of the Lyocell process was not really solidified in the air gap and a gel or ribbery state was formed.

The Online Measurement of Lyocell Fibers and Investigation of Elongational Viscosity of Cellulose N-methylmorpholine-N-oxide Monohydrate Solutions

The Online Measurement of Lyocell Fibers and Investigation of Elongational Viscosity of Cellulose N-methylmorpholine-N-oxide Monohydrate Solutions

The impact of urea on viscosity of hydroxethyl cellulose and observed mobility of deoxyribonucleic acids.

The influence of urea on the viscosity of hydroxyethyl cellulose (HEC), and the state and separation of double-stranded DNA, was studied by viscometry, fluorometry, and capillary electrophoresis. The results show that double logarithm plots of specific viscosity against the volume fraction of HEC in very dilute polymer solutions are linear, the slopes of which decrease from 0.96 in 0M to 0.29 in 7M urea. The linear regression plots converge at 0.0029 g/mL, the entanglement threshold of HEC. The inclusion of urea in HEC solution thus provides an accurate method of determining its entanglement threshold from such plots. Above the entanglement threshold of HEC, urea has no effect on the specific viscosity of HEC. Results also show that urea has no effect on double-stranded DNA. No change in fluorescence was observed when increasing amounts of urea were added to a fixed concentration of DNA. To examine the influence of urea on the migration of DNA in HEC, the separation of DNA was carried out by polymer-solution capillary electrophoresis in HEC solutions containing 0 or 7M urea using unmodified capillary. Observed mobilities were used in data reduction. It was found that a parallel relationship exists between the observed mobilities and the true mobilities. In buffers containing no urea, the pseudo-free solution mobility appears to be independent of the DNA size. It was also observed to be independent of the electric field below 300 V/cm, but relates exponentially to it in 7M urea. The pseudo-retardation constants obtained by Ferguson-like plots were observed to be positive for smaller DNA molecules below 300 V/cm and increasing linearly with electric field in 0M urea, but nearly constant in 7M urea.

Miscibility study of cellulose acetate/carboxylated poly(vinyl chloride) blend in cyclohexanone by viscosity, ultrasonic velocity, refractive index, and polarizing microscopic methods

The viscosity, ultrasonic velocity, refractive index, and density of cellulose acetate/carboxylated poly(vinyl chloride) (CA/C-PVC) blends in cyclohexanone, a common solvent, were measured at 30°C. After casting films of the blend for a 50:50 composition, polarizing micrographs were taken. Using the viscosity data, the interaction parameters were computed by employing two different equations. These values indicated that the CA/C-PVC blend is miscible. This was confirmed by ultrasonic, refractive index, density, and polarizing microscopic methods. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 557–561, 2001

In vitro modified release of acyclovir from ethyl cellulose microspheres

The aim of this study was to demonstrate a sustained-release microparticulate dosage form for acyclovir via an in vitro study. Ethyl cellulose was selected as a model encapsulation material. All of the microspheres were prepared by an oil-in-water solvent evaporation technique. A 23 full factorial experiment was applied to study the effects of the viscosity of polymer, polymer/drug ratio, and polymer concentration on the drug encapsulation efficiency and the dissolution characteristics. The encapsulation efficiency of acyclovir in microspheres was in the range of 20.0-56.6%. Increase in the viscosity of ethyl cellulose and the ratio of CH2Cl2/ethyl cellulose increased drug encapsulation efficiency. The drug continuously released from microspheres for at least 12 h, and the release rate depended on the pH of the release medium. The sustained release characteristic was more prominent in the simulated intestine fluid than in the simulated gastric fluid. A faster release of drug was observed when a high viscosity polymer was used. The decomposition of acyclovir significantly decreased when encapsulated by ethyl cellulose, especially when stored at 37 and 50 °C.

Rheology of carboxymethylcellulose made from bacterial cellulose

AbstractPartly as a result of the high solution viscosity of bacterial cellulose, carboxymethylcellulose (CMC) derived from this material exhibits shear‐thinning and thixotropic properties. With suitable sample treatment, the CMC solution shows gel‐like rheology suggesting the presence of a three‐dimensional network. This behavior is consistent with heterogeneous substitution of the carboxymethyl functionality on the polymer chains. For comparison, bacterial cellulose is also degraded by either acid or ultrasound to reduce its molecular weight and converted to CMC. The flow behavior of the resulting CMC solutions is nearly Newtonian with slight shear thinning but no thixotropy, suggesting that the carboxymethylation reaction is almost random.

VISCOMETRIC STUDY OF CELLULOSE IN PF/DMSO SOLUTION

Cellulose samples were found to be soluble in PF/DMSO to form a genuine dilute solution without suffering obvious degradation under adequate conditions. The Mark-Houwink-Sakurada equation for cellulose in PF/DMSO at 30°C obtained here was [η] = 3.01 × DP0.81 where [η] is in the unit of cm3·g−1. The intrinsic viscosity of cellulose in Cadoxen, FeTNa, PF/DMSO and DMAc/LiCl was in the following order: [η]DMAc LiCl >[η]PF/ DMSO>[η]FeTNa >[η]Cadoxen, and the same tendency for the values of the parameter α. The intrinsic viscosity can be considered as an indication of the dimension of cellulose macromolecular chains in different solvent systems.

Enhancement of pH-stability of a low molecular mass endoglucanase from Fusarium oxysporum by protein pegylation

The stability of the low molecular mass endoglucanase (23.2 kDa) from Fusarium oxysporum at alkaline pH was enhanced by chemical modification. Two distinct types of amino acid-specific modifiers were used. The first, either cyanuric chloride activated polyethylene glycol (CC–PEG) or polyethylene glycol succinimidyl succinate active ester (SS–PEG), react (more or less specifically) with protein amino groups. The second type, maleimide polyethylene glycol (Mal–PEG), is specific for cysteinyl residues. The enzyme lost almost all of its activity when modified with CC–PEG, whereas no inactivation was observed with SS–PEG and Mal–PEG. The modified endoglucanase showed remarkably enhanced alkaline pH stability. When acting upon cello-oligosaccharides and 4-methylumbelliferyl cello-oligosaccharides, the enzyme preferentially cleaved the internal glycosidic bonds. The modified enzymes mediated a decrease in the viscosity of carboxymethyl cellulose (CMC) associated with the release of only small amounts of reducing sugar. Thus, the modified enzyme retains the endo character of the native enzyme.

Two cellulases, CelA and CelC, from the polycentric anaerobic fungus Orpinomyces strain PC-2 contain N-terminal docking domains for a cellulase-hemicellulase complex.

Two cDNAs encoding two cellulases, CelA and CelC, were isolated from a cDNA library of the polycentric anaerobic fungus Orpinomyces sp. strain PC-2 constructed in Escherichia coli. Nucleotide sequencing revealed that the celA cDNA (1,558 bp) and celC cDNA (1,628 bp) had open reading frames encoding polypeptides of 459 (CelA) and 449 (CelC) amino acids, respectively. The two cDNAs were 76.9 and 67.7% identical at the nucleotide and amino acid levels, respectively. Analysis of the deduced amino acid sequences showed that starting from the N termini, both CelA and CelC had signal peptides, which were followed by noncatalytic repeated peptide domains (NCRPD) containing two repeated sequences of 33 to 40 amino acid residues functioning as docking domains. The NCRPDs and the catalytic domains were separated by linker sequences. The NCRPDs were homologous to those found in several hydrolases of anaerobic fungi, whereas the catalytic domains were homologous to the catalytic domains of fungal cellobiohydrolases and bacterial endoglucanases. The linker sequence of CelA contained predominantly glutamine and proline residues, while that of CelC contained mainly threonine residues. CelA and CelC did not have a typical cellulose binding domain (CBD). CelA and CelC expressed in E. coli rapidly decreased the viscosity of carboxymethyl cellulose (CMC), indicating that there was endoglucanase activity. In addition, they produced cellobiose from CMC, acid-swollen cellulose, and cellotetraose, suggesting that they had cellobiohydrolase activity. The optimal activity conditions with CMC as the substrate were pH 4.3 to 6.8 and 50 degrees C for CelA and pH 4.6 to 7.0 and 40 degrees C for CelC. Despite the lack of a CBD, CelC displayed a high affinity for microcrystalline cellulose, whereas CelA did not.

Effect of Formulation Variables on Dissolution Profile of Diclofenac Sodium from Ethyl- and Hydroxypropylmethyl Cellulose Tablets

AbstractThe effects of formulation variables on the release profile of diclofenac sodium from ethyl cellulose (EC) and hydroxypropylmethyl cellulose (HPMC) matrix tablets were investigated. With increase in viscosity of ethyl cellulose used in nonaqueous granulation, a decrease in drug release from the tablets was observed, while the percentage of fines articles passed through 60 mesh) in the granulation had a significant effect on the dissolution profile. Granules containing 15% fines exhibited slow release of the drug in comparison to those containing 30% fines with EC matrices. An analysis of kinetics of drug release from hydrophobic EC matrix showed Fickian diffusion regulated dissolution. Drug release from HPMC tablets followed an apparent zero-order kinetics.