Showing papers on "Viscometer published in 1985"

The differential viscometer. II. On‐line viscosity detector for size‐exclusion chromatography

Abstract: The new technique of differential viscometry measures directly the specific viscosity of a solution by subtracting the contribution of solvent in a balanced capillary bridge. The present work adapts the differential viscometry principle to the design of a viscosity detector for use in size-exclusion chromatography. It is shown that the resulting viscosity detector possesses excellent sensitivity and baseline stability with a minimum detectable specific viscosity of 2.7 × 10−5. The viscosity detector can be operated together with a refractive index detector to determine the intrinsic viscosity of polymer solute fractions as they elute from the SEC column. The bandspreading of the viscosity detector is compared to the refractive index detector by measuring the peak width of a compound having a single discrete molecular weight. The peak width at half-height was 0.29 mL for the viscosity detector and 0.25 mL for the refractive index detector.

Variation of viscosity with temperature and composition in the plagioclase system

Abstract: The viscosities of supercooled melts of 13 different plagioclase compositions have been measured in the range 1013–108 dPas with a micro-penetration viscometer. Application of the most common empirical and theoretical viscosity-temperature models to the present data and plagioclase viscosity data available from the literature showed that the configurational entropy theory represents the best approach. Using this theory together with an entropy of mixing term evaluated from a modified “two-lattice” mixing model, the viscosities of intermediate plagioclase compositions have been calculated as a function of temperature and anorthite content solely from the appropriate data of the end members albite and anorthite. The agreement between experimental and calculated viscosity data is excellent.

Evaluation of the separate contributions of viscosity and sweetness of sucrose to perceived viscosity, sweetness and bitterness of vermouth

Abstract: The separate effects of sweetness and viscosity of sucrose on the sensory properties of vermouth were evaluated in systems: (1) varying in sucrose concentration and viscosity (2) with constant sucrose concentration but varying in viscosity, and (3) constant viscosity, but varying sucrose concentration. Twenty-one trained judges rated oral viscosity, sweetness and bitterness, while the physical viscosity of the Newtonian systems was measured by capillary viscometry. Both perceived sweetness and oral viscosity increased, while bitterness decreased as sucrose was increased, and as the physical viscosity of the vermouths increased. However, samples in which viscosity was increased by the nonsweet Polycose® were rated sweeter and less bitter than vermouth solutions of the same sucrose concentration, but lower physical viscosity. Similarly, when vermouths of identical viscosity were compared, the vermouths with higher sucrose concentration were judged to be more viscous. Viscosity alone contributed 20-30% of the perceived increase in sweetness due to sucrose addition. The effect of viscosity in reducing bitterness was of the same magnitude. The increase in perceived viscosity caused by addition of sucrose arose from approximately equal contributions of physical viscosity and sweetness of sucrose.

The differential viscometer. I. A new approach to the measurement of specific viscosities of polymer solutions

Abstract: A new type of solution viscometer is described that measures the specific viscosity directly. This is accomplished with a balanced network of four capillaries arranged in a manner analogous to a Wheatstone bridge. A differential pressure transducer measures the increase in pressure across the bridge when a solution is injected into one of the capillaries while solvent flows continuously in the other three capillaries. The differential pressure is proportional to the specific viscosity of the solution. The differential viscometer is about 10 times more sensitive than a conventional glass tube viscometer, permitting precise measurements of specific viscosities of 0.01 or less. The measurements are also inherently fast, averaging about 3 min per sample. Precision is about 1% RSD. Accuracy was investigated by running standard solutions of sucrose in water, polystyrenes in toluene, and polyethylenes in decalin. The agreement was within 2–3% of the standard values in most cases.

Rheological Characterization of Grain Legume Pastes and Effect of Hydration Time and Water Level on Apparent Viscosity

Abstract: An extrusion capillary viscometer was employed to obtain shear stress-shear rate data of two types of cowpea pastes, traditional and experimental. The power law model was found to describe adequately flow behavior of the pastes with consistency coefficients of 77.45 and 59.02, and flow behavior indices of 0.456 and 0.458 for experimental and traditional pastes, respectively. Effect of hydration time (0 - 180 min) and water level (54 - 62%) on the apparent viscosity of experimental paste was determined by extrusion capillary and Brookfield viscometers with correlation coefficient of 0.953. Water level had a significantly greater effect than hydration time on apparent viscosity of cowpea paste.

Transport properties of nonelectrolyte liquid mixtures—VII. Viscosity coefficients for isooctane and for equimolar mixtures of isooctane + n-octane and isooctane + n-dodecane from 25 to 100°C at pressures up to 500 MPa or to the freezing pressure

Abstract: Changes in the high-pressure self-centering falling-body viscometer system, and the new automated data logging system, are described. Viscosity coefficient measurements made with an estimated accuracy of ± 2 % are reported for isooctane and for equimolar mixtures of isooctane + n-octane and isooctane + n-dodecane at 25, 50, 75, and 100°C at pressures up to 500 MPa or to the freezing pressure. The pressure dependence of the results is found to be represented equally well by the recent equation of Makita and by a free-volume form of equation. The Grunberg and Nissan equation gives a good fit to the mixture viscosity coefficient data.

Experimental study and analysis of a slit die viscometer

Abstract: A slit die viscometer (SDV) was built and evaluated extensively. A major advantage of the SDV is the ability to measure in-line rheological data in a continuous fashion, using a setup that most closely approximates the conditions encountered in a real extrusion process. Comparisons will be presented of viscosity data of the SDV to data from a capillary rheometer (CR) and a Rheometrics Mechanical Spectrometer (RMS). Viscosity values as measured on the SDV tend to be lower than those measured on the CR and RMS. Possible reasons for this disagreement will be discussed. The effect of temperature on viscosity, the effect of pressure on viscosity, and the effect of compressibility will be analyzed in detail. It will be shown that these effects can be substantial, particularly with certain types of polymers. Finally, the feasibility of using the slit die viscometer to determine first normal stress differences will be explored.

On the penetration of a hot diapir through a strongly temperature-dependent viscosity medium

Abstract: The ascent of a hot spherical body through a fluid with a strongly temperature-dependent viscosity has been studied using an axisymmetric finite element method. Numerical solutions range over Peclet numbers of 0.1 - 1000 from constant viscosity up to viscosity variations of 100,000. Both rigid and stress-free boundary conditions were applied at the surface of the sphere. The dependence of drag on viscosity variation was shown to have no dependence on the stress boundary condition except for a Stokes flow scaling factor. A Nusselt number parameterization based on the stress-free constant viscosity functional dependence on the Peclet number scaled by a parameter depending on the viscosity structure fits both stress-free and rigid boundary condition data above viscosity variations of 100. The temperature scale height was determined as a function of sphere radius. For the simple physical model studied in this paper pre-heating is required to reduce the ambient viscosity of the country rock to less than 10 to the 22nd sq cm/s in order for a 10 km diapir to penetrate a distance of several radii.

Parameters affecting viscosity as a quality control for frozen fish

Abstract: The measurement ofapparent viscosity may be an appropriate method of quality control for myosystems undergoing frozen storage. Our experiment studied parameters affecting the measurement ofapparent viscosity of homogenated muscle of Allantic cod, Gadus morhua, in 5 percent NaCl solution as a quality control method for frozen fish. Parameters like the ratio of muscle to saline solution, pH, homogenation time and method, time elapsing between homogenation and viscosity measurement, and temperature were studied to establish and standardize the optimum conditions for measurement. On the basis of the results obtained, these conditions were: Ratio of muscle to 5 percent NaCl solution, 1:4; homogenation for 1 minute; a pH ofbetween 65 and 7; a time between homogenation and viscosity measurement of30-60 minutes; and a blending/viscosity measurement temperature of between 2° and 5°C. 47(4), 1985 both protein solubility and emulsifying capacity in frozen muscle. It has also been found, and this is especially true for white fish (i.e., blue whiting, cod, hake), that the values obtained using this technique in tests of frozen muscle during the storage period are highly significant, such that the sets of measurement readings provide a clear picture of the quality of the frozen product. Other authors (Groninger et aI., 1983) have employed a similar method of measuring the functional properties of proteins. Therefore, this technique would seem to be appropriate for use as an index of the quality of frozen fish protein. Moreover, the speed and ease of the method, and the fact that it can be performed using relatively unsophisticated equipment, make it ideal for use both in the laboratory and in industrial situations. Our study examined the influence of various parameters affecting apparent viscosity on this quality control method. Materials and Methods Atlantic cod, Gadus morhua, caught 5-7 days earlier and preserved chilled, was purchased at a local market. The muscle was minced using a mincer with plate orfices 5 mm in diameter. The mince was divided into 300 g lots which were packaged on trays wrapped in aluminium foil. The samples were frozen in a tunnel freezer at -30°C with an air flow of 5 m/second and then vacuum-packed and stored at -24°C for the 5 days during which tests were made. The apparent viscosity (Y)app) was measured using a Brookfield2 model 'Mention of trade names or commercial firms does not imply endorsement by the National Marine Fisheries Service, NOAA. RVT rotary viscometer with flat spindles numbers 2,3, and 4 at a speed of 20 rpm. Measurements were taken after 3 minutes of spindle operation, and at least four replicates were performed. The basic steps of this procedure are diagrammed in Figure 1, and the standard conditions applied in the procedure are set out below: 1) Ratio g of muscle:ml 5 percent NaCI solution: 1:4. 2) pH: 6.5-7.0. 3) blender, speed setting, and time: Omni-mixer, setting 7, 1 minute. 4) homogenate temperature: 3-5°C. 5) standing time: 30 minutes. In addition to the standard conditions, the following variations were also tested: 1) Ratio g of muscle:ml 5 percent NaCI solution: 1:4, 1:6, 1:8, and 1:10, corresponding to 20.0, 14.3, 11.1, and 9.1 g of fish/100 ml of homogenate. 2) pH: 4.85, 5.53, 6.57, 6.61, 6.70, 6.93, 7.60, 8.33, and 9.10. 3) Blender and blending time: Omnimixer (1, 2, and 3 minutes) and Ultraturrax (1 minute at middle speed setting). 4) Blending/viscosity measurement temperature (oq: 2.2, 3.6, 4.8, 10.0, 14.5, 14.9, 15.3, 17.5, 21.3, and 25.0. 5) Standing time (minutes): 0, 30, 70, 100, 165, 240, and 300. 6) Homogenate centrifuging conditions: 3 minutes at 3,000 rpm at 3°C. Regression curves were calculated by computer; the significance levels of the The authors are with the Instituto del Frfo, Ciudad Universitaria, 28040 Madrid, Spain.

Rheological behaviour and microstructure of stir-casting zinc-aluminium alloys

Abstract: The influence of processing variables on the rheological and microstructural behaviour of stir-cast (rheocast) ZA-27 alloy (Zn-27 wt % Al-2wt % Cu) has been investigated experimentally. A concentric cylinder viscometer with shear rate range up to 650 sec−1 was used to measure the apparent viscosity of the slurries. During continuous cooling and at high shear rates (300–640 sec−1), non-dendritical materials obey the power-law fluid model, i.e.\(\eta _{\text{a}} = k\dot \gamma ^n \) where ηa is the apparent viscosity and\(\dot \gamma \) the shear rate. At lower shear rates (125 sec−1), the slurries display dendritical-liquid mixture with viscosity up to 50 poises. Microstructural studies of continuously cooled materials reveal a clear tendency of primary particles to cluster. This phenomenon could be explained by the reduction of the amount of entrapped liquid in the particles.

Measurements of the viscosity of sulfur hexaflouride up to 100 bar by a capillary-flow viscometer

Abstract: A new capillary-flow viscometer has been developed for the precise determination of the viscosity of gases in the vicinity of the gas-liquid critical point. An important feature of the viscometer is the possibility to operate at pressure differences as low as 1 mbar. The apparatus, consisting mainly of a pressure vessel with the capillary, a differential pressure meter and a specially designed air thermostat has been described in detail together with the experimental procedure. The viscosity has been computed with a modified Poiseuille formula for compressible fluids. Measurements on sulfur hexaflouride are performed at 1 bar as a function of temperature between 298 and 333 K and at 333 K as a function of pressure up to 100 bar. Besides, for the purpose of calibration, some measurements are performed on nitrogen at several pressures and temperatures. The accuracy of the measurements is estimated to be about 0.1%. The agreement with previous results is found to be fairly satisfactory in several cases.

Differential pressure capillary viscometer for measuring viscosity independent of flow rate and temperature fluctuations

Abstract: A means for measuring either the intrinsic or inherent viscosity of a solute in solution with a solvent which is independent of flow rate and temperature fluctuations. The solution is passed through one capillary tube and the solvent through a second capillary, and the pressure drop across each is measured. Signals corresponding to each pressure drop measurement are fed to an amplification means such as a logarithmic amplifier where they are processed to determine either the intrinsic or inherent viscosity of the solute independent of flow rate and temperature fluctuations. The viscosity measuring means may also be used together with size exclusion chromatrography to determine the molecular weight distribution of polymer materials. It may also be used to measure the relative viscosity of a sample liquid and a reference liquid, and to determine the viscosity of the sample liquid independent of flow rate and temperature fluctuations.

Transport properties of nonelectrolyte liquid mixtures—VI. Viscosimetric study of binary mixtures of hexafluorobenzene with aromatic hydrocarbons

Abstract: Viscosity coefficients for binary mixtures of hexafluorobenzene with benzene, toluene, para-xylene, and mesitylene have been measured along the saturation line at temperatures from 15 to 120°C using specially designed capillary viscometers. Densities were measured using a pyknometer and volume-change apparatus. Deviations of the viscosities from a rectilinear dependence on mole fraction are consistent with enhanced interactions between unlike species, which increase with increasing number of methyl groups on the aromatic hydrocarbon and decrease with increasing temperature. The application of the Grunberg and Nissan equation, the Hildebrand equation, and energy of activation theories to these results is examined.

Rheological properties of rice flour slurries and pastes.

Abstract: Apparent viscosity of rice (high amylose var. (i) Taichung Native 1 and low amylose var. (ii) Changlei) pastes and slurries was measured with a coaxial cylinder viscometer. The cooked pastes (cooked at 95 degree C for 2 min and measured at 27 degree C) of both the rice var. showed thixotropic loops in plots of viscosity vs. shear rate. Viscosities of both the pastes increased with concn. but the curve was steeper with (i) than with (ii). Viscosity was always higher at 27 degree C than at 60 degree C. In another set of experiments viscosities of the slurries of 8 quality types of rice (ranging from Type 1 which cooks hard and flaky and Type VIII which cooks very soft and sticky) were tested after cooking at 95 degree C for 2 min. It was found that at 10 and 12% (dry basis) concn. of the paste, apparent viscosity decreased continuously from Type I to Type VIII. At 3% concn. apparent viscosity decreased from Type VIII to Type I rice. But between 5 and 8% paste concn. the viscosities were close together. With uncooked slurry, the viscosity was tested at 20, 25 and 30% concn. (dry basis) as the readings were low and unreliable at lower concn. The results indicated that the apparent viscosity was highest for Type VIII and lowest for Type I rice in that order. Uncooked slurries of rice flour dispersed in 2% carboxymethyl cellulose at 10-15% concn. behaved similarly to cooked rice paste of 3% concn.

Viscosity Measurements for the Nematic Liquid Crystal PAA

Abstract: An oscillating plate viscometer was used to measure the viscosities of PAA with the molecular axis oriented by an electromagnet. The experimental apparatus allowed measurement when the magnet was o...

Rheological techniques to evaluate the shelf-stability of starch-thickened, strained apricots

Abstract: The rheological behavior of strained apricots thickened with modified tapioca starch was investigated using mixer viscometry techniques. Initially, the sample showed irreversible thixotropy which was quantified by evaluating time-dependent torque decay. Mechanically degraded samples had time-independent properties and were evaluated as power-law fluids. Rheological techniques developed were successfully used to evaluate the textural shelf-life of strained apricots thickened with different types of modified tapioca starch.

An automated falling-cylinder high pressure laser-Doppler viscometer

Abstract: A microcomputer-controlled optical viscometer for the measurement of the viscosity of liquids under pressure is reported The viscometer is of the falling-cylinder type with a measurement range greater than six decades making it well suited for viscosity measurements of liquids with very large viscosity pressure coefficients Results are presented for a range of alkanes and polypropylene glycol derivatives

Experimental Test of Hydrodynamic Theories for Nematic Liquid Crystals

Abstract: For nematic phases of pentacyanobiphenyl (5CB) and 4-n-methoxybenzoate-4-n-pentylphenyl (MBPP) the viscosity coefficients have been determined by means of a flat capillary viscometer. The detailed information on the experimental set-up has been published elsewhere. The measurements enable the calculation of all Leslie coefficients αi i = 1 - 6. Having the Leslie coefficients determined, the twist viscosity coefficient [mgrave]1 can be calculated. The comparison of the calculated and experimentally determined twist viscosity coefficient may serve as a test of validity of the Parodi relaxation: α2 + α3 = α6 - α5. The validity of this relation was additionally proved by means of comparison of the results of the viscometric measurements and the results of measurements of the attenuation of longitudinal ultrasound waves.

A simple extensional viscometer

Abstract: An extensional viscometer is described in which the liquid filament leaving a capillary is subjected to a stretching deformation. In order to keep the flow rate through the capillary unaltered upon inception of stretching, the pressure head at the capillary entrance has to be reduced by an amount equal to the extensional viscoelastic stress at the capillary exit. This affords a simple means of measuring small fluid forces such as those that occur in the stretching of dilute polymer solutions. Since stretch rates can be obtained from a knowledge of the mass flow rate and the filament diameter profile, extensional viscosities can be computed. The efficacy of the technique is demonstrated by obtaining the anticipated results for Newtonian liquids.

Measurement of the viscosity of trifluoroethanol and its aqueous solutions under high pressure.

Abstract: The viscosity of pure 2, 2, 2 trifluoroethanol and its aqueous solutions of 85 mol% and 60 mol% has been measured in the temperature range 273 - 453 K and at pressures up to 40 MPa by a closed circuit capillary viscometer. No experimental data are reported for the pressure dependence of the viscosity of these mixtures so far. The experimental error of the present measurement is estimated at ±1.1%. The measured data were correlated with an equation of the viscosity in terms of temperature and pressure for each mixture. At atmospheric pressure, additional measurements were performed with the aid of a Ubbelohde viscometer over the whole range of composition was confirmed.

The role of solvent viscosity in dilute-solution polymer rheology

Abstract: Capillary viscometry was performed on dilute non-Newtonian solutions of monodisperse polystyrene in theta solvents The solvents, blends of low-molecular-weight polystyrene with styrene, had viscosities (η s ) that were varied from 022–27 Pa s Data reduction of the dilute limit, [η]/[η 0 ] vs β = [η 0 ]η s M γ / RT (where γ is shear rate) revealed a parametric dependence on η s that has not before been reported and is not predicted by most molecular theories of polymer dynamics It is suggested that an internal viscosity model can explain such a phenomenon

Production of calcium carbonate

Abstract: PURPOSE: To produce columnar CaCO 3 having calcite type crystal shape advantageously on an industrial scale by stirring and aging CaCO 3 slurry having higher viscosity above a specified value after producing the slurry by the gas/liquid reaction between gaseous CO 2 and Ca(OH) 2 . CONSTITUTION: In the production of CaCO 3 by the gas/liquid reaction between gaseous CO 2 and Ca(OH) 2 the slurry having ≥1,000cP viscosity measured by a B type viscometer at 60rpm is aged further while stirring so as to make the whole body of the slurry uniform. Thus, calcite type columnar CaCO 3 is produced advantageously on an industrial scale. When the obtd. CaCO 3 is used as coating pigment for printing white paper, the gloss of the coated paper before and after printing, ink receptivity, and the viscosity of the coating material at high shear plane are all satisfied at the same time. Moreover, when the CaCO 3 is used as filler for tissue paper, expensive TiO 2 is saved because the CaCO 3 has superior opacity and whiteness as compared to conventional spindle-shaped coating material. COPYRIGHT: (C)1987,JPO&Japio

A Viscometer for Fast Polymerizing Systems

Abstract: A parallel‐disk viscometer capable of measuring the viscosity rise isothermally for fast polymerizing systems has been designed and characterized. Criteria for isothermal operation are given. The viscometer has been specifically designed for polyurethane chemical systems used in reaction injection molding (RIM) and is adaptable enough to be coupled directly to various commercial RIM machines. Some minor modifications may be needed for other reactive systems. The viscometer in its present design is not highly precise, but is rugged and inexpensive.

Impact strength and melt viscosity of bisphenol-a polycarbonate and styrene-maleic-anhydride copolymer blends

Abstract: Mixtures of 90, 80, and 70 percent by weight bisphenol-A-polycarbonate (PC) and 10, 20, and 30 percent by weight styrene maleic anhydride (SMA) copolymer were melt-blended in a single screw extruder. Differential scanning calorimetry (DCS) and scanning electron microscopy (SEM) were used to determine the miscibility of the blends. The viscosity, as a function of shear rate and temperature, was measured by an Instron capillary viscometer. The notched impact strength as a function of temperature was measured by an Izod impact tester. The results of DSC showed two glass transition temperatures which merged slightly towards each other, indicating marginal miscibility of these blends. There was a decrease in viscosity as the fraction of SMA copolymer was increased. The most significant decrease occurred with the initial addition of SMA copolymer. The viscosity also decreased with increases in temperature. The impact strength of the blends was also dependent on SMA copolymer content. The blends showed six to ten times lower impact strengths at room temperature than the 100 percent polycarbonate. SEM analysis helped to determine the reason why the impact strength was lower for the blends. High magnification showed the presence of SMA copolymer inclusions dispersed throughout the PC matrix. These inclusions, which increased in size as SMA copolymer content was increased, acted as defects in the system.