Showing papers on "Viscometer published in 1997"

Viscosities of fatty acids, triglycerides, and their binary mixtures

Abstract: Viscosity data have been obtained as a function of temperature for seven fatty acids (pelargonic, capric, lauric, myristic, palmitic, stearic, and oleic) and four triglycerides (tricaprilin, tripalmitin, tristearin, and triolein) and their binary mixtures at temperatures from above their melting points to 90°C. The viscosity measurements were performed by using Cannon Fenske glass capillary kinematic viscometers. Modified versions of the Andrade equation were used to correlate the kinematic viscosities of pure fatty acids and pure triglycerides. The MacAllister method was used for their binary mixtures. The correlation constants are valuable for designing or evaluating chemical process equipment, such as heat exchangers, reactors, distillation columns, and process piping.

The effects of low-density lipoprotein and high-density lipoprotein on blood viscosity correlate with their association with risk of atherosclerosis in humans

Abstract: 1. Increased blood or plasma viscosity has been observed in almost all conditions associated with accelerated atherosclerosis. Cognizant of the enlarging body of evidence implicating increased viscosity in atherogenesis, we hypothesize that the effects of low-density lipoprotein and high-density lipoprotein on blood viscosity correlate with their association with risk of atherosclerosis. 2. Blood viscometry was performed on samples from 28 healthy, non-fasting adult volunteers using a capillary viscometer. Data were correlated with haematocrit, fibrinogen, serum viscosity, total cholesterol, high-density lipoprotein-cholesterol, triglycerides and calculated low-density lipoprotein-cholesterol. 3. Low-density lipoprotein-cholesterol was more strongly correlated with blood viscosity than was total cholesterol (r = 0.4149, P = 0.0281, compared with r = 0.2790, P = 0.1505). High-density lipoprotein-cholesterol levels were inversely associated with blood viscosity (r = -0.4018, P = 0.0341). 4. To confirm these effects, viscometry was performed on erythrocytes, suspended in saline, which had been incubated in plasma of various low-density lipoprotein/high-density lipoprotein ratios. Viscosity correlated directly with low-density lipoprotein/high-density lipoprotein ratio (n = 23, r = 0.8561, P < 0.01). 5. Low-density lipoprotein receptor occupancy data suggests that these effects on viscosity are mediated by erythrocyte aggregation. 6. These results demonstrate that the effects of low-density lipoprotein and high-density lipoprotein on blood viscosity in healthy subjects correlate with their association with risk of atherosclerosis. These effects on viscosity may play a role in atherogenesis by modulating the dwell or residence time of atherogenic particles in the vicinity of the endothelium.

Hydrophobic Interactions of Poly(N-isopropylacrylamide) with Hydrophobically Modified Poly(sodium acrylate) in Aqueous Solution

Abstract: The interactions between poly(N-isopropylacrylamide), PNIPAM, and poly(sodium acrylate) hydrophobically modified with octadecyl groups, HMPA, in aqueous solutions, were studied by using viscometry and turbidimetry. The viscosity of mixtures of the two polymers, at 25 °C, may be several orders of magnitude higher than the viscosity of the corresponding mixtures of PNIPAM with the unmodified precursor poly(sodium acrylate). The higher the modification degree of the HMPA, the greater the viscosity enhancement. Furthermore, increasing the molar mass of PNIPAM leads to a more pronounced viscosity increase. The elevation of the phase separation temperature of PNIPAM in the PNIPAM/HMPA mixtures reveals, also, the development of interactions between the two polymers. These interactions are temperature-dependent, and a thermothickening behavior has been observed with increasing temperature.

Viscosity of toluene and benzene under high pressur

Abstract: The viscosity of toluene and benzene was measured at the temperatures of 298.15, 323.15, 348.15, and 373.15 K (ITS-90) from atmospheric pressure up to 200 MPa, by a torsionally vibrating quartz-crystal viscometer, with an estimated accuracy of 0.5%. The experimental data for each temperature were fitted with a Tait-like equation, by a non linear iterative program based on the Marquardt Levenberg method. A comparison between present data and available data from other authors, whenever possible, was made in terms of the dispersion of each data set with respect to the Tait-like equation.

On-line control of a chemical process plant

Abstract: A process plant for the manufacture of halobutyl rubber is provided with online monitoring and control of the process parameters to control the properties of the product. It incorporates an in situ measurement system that does not require the removal of any sample material from the process. It uses a Fourier Transform Near Infrared (FTNIR) spectrometer, fiber-optic cables, a viscometer for measuring solution viscosity and a Resistance Temperature Device (RTD) for temperature measurement. An online real-time analyzer system using a Constrained Principal Spectral Analysis program predicts the property of the polymer product and provides the process control system with analysis of the data using derived relationships between the physical properties of the polymer and these spectral measurements and the measured values of fluid viscosity and temperature. Differences between the predicted and desired property of the product are used to control process parameters. The method can be used for a variety of chemical process plants.

Extensional viscosity from entrance pressure drop measurements

Abstract: Extensional rheological properties are important in characterization and processing of polymeric liquids. The use of entrance pressure drop to obtain extensional viscosity is particularly attractive because it can be applied to both low and high viscosity liquids using the Bagley correction obtained from a conventional capillary rheometer. Low density polyethylene of three different melt index values, including IUPAC-X (a different batch of IUPAC-A), and a high density polyethylene were tested using a commercial capillary rheometer. The entrance pressure drop (ΛP en ) was obtained with a “zero-length” orifice die with an abrupt contraction. The contraction ratio was 12:1. Predictions from several approximate analyses to calculate the uniaxial extensional viscosity ηu (using an axisymmetric contraction) from ΔP en were compared. These comparisons are summarized in the appendices. Due to the transient nature of contraction flows, η u is also a function of the strain (ɛ). This was examined by comparing η u from ΔP en (Cogswell's analysis was chosen for convenience) with transient extensional viscosity (η u +) at different magnitudes of ɛ from fiber-windup technique (Padmanabhan et al., 1996). η + at ɛ≈ 3 was found to be close to η u from ΔP en (using Cogswell's analysis) for two LDPE samples that had fiber-windup data available. The magnitude of the strain in the contraction did not vary with strain rate.

Temperature and Density Dependence of the Viscosity of Octane and Toluene

Abstract: Fluids of larger polyatomic molecules do not well fit the hard sphere model of dense fluids as their liquid range, reduced in terms of relative molecular volumes, usually extends well beyond the freezing density of the hard sphere fluid. Even where overlap occurs, the density dependence is observed to be not as simple as that of the model. It is for this reason that empirical functions for the density dependence of the transport properties have been developed. Application of such correlations has thrown some doubt on previous high-pressure measurements of the viscosity of liquid octane and toluene. New measurements have been made for octane between 283 K and 348 K and for toluene at 298 K and 323 K at pressures up to approximately 375 MPa with a falling-body viscometer. These are supplemented by pVT measurements for octane between 278 K and 298 K, which have been used to improve an earlier equation of state. The viscosity results are compared with earlier data using a general correlation method for molecu...

Viscosity of carbon dioxide in the liquid phase

Abstract: The viscosity coefficient of liquid carbon dioxide has been measured along isotherms from the triple-point temperature (217 K) up to the critical temperature (304 K) at temperatures of 220, 230, 240, 260 and 280 K by means of a vibrating-wire viscometer The measurements extended beyond both phase-transition lines into the coexistence region (superheated liquid) and into the solid range (undercooled liquid) The accuracy of the measurements is estimated to be 1% The agreement with data of other authors is rather good For the most part, the results show a linear pressure dependence in three neighbouring pressure ranges for the various isotherms with a common intersection with the negative pressure axis pi The fluidity, the reciprocal of the viscosity, shows a linear dependence of the molar volume in adjacent density ranges After reduction of the molar volume with the volumes of close packing, three sets of linear functions result with common intersections of the axis VB The aim of the present investigation was to produce a new set of viscosity data on request of the Subcommittee on Transport Properties of the International Union of Pure and Applied Chemistry in order to provide supplementary data for the improvement of representative equations for the viscosity of carbon dioxide The representation of the fluidity as a linear function of the reduced molar volume in various density ranges provides us with the possibility of presenting a correlation protocol which produces the viscosity of liquid carbon dioxide within about 1% For this purpose, a consistent set of “volumes of close packing” is obtained by means of a comparison with the results of computer simulations The combination of the two types of linear relations gives reason to interpret pi as the internal pressure and VB as the excluded volume This interpretation enables us to state that, at constant temperature, the viscosity coefficient is directly proportional to the thermal pressure, ie the sum of the measured pressure and the internal pressure, and thereby proportional to the number of collisions of the molecules The viscosity coefficient is, thus, determined by the number of collisions per unit time and volume, and by the efficiency of the exchange of momentum during a collision From the linearity of the fluidity as a function of the molar volume, we conclude that the number of collisions is inversely proportional to the free volume V − VB Thus our measurements of the viscosity of liquid carbon dioxide lead to simple views on this phenomenon

Experimental study of steady and unsteady free surface flows with water-clay mixtures

Abstract: The steady and unsteady free-surface flow of hyperconcentrated water-kaolinite clay mixtures is analysed experimentally. These mixtures exhibit non-Newtonian behaviour if volumetric concentrations of solid particles exceed about 10%. The viscosity-concentration correlations, determined by rotary viscometer, indicate that the Bingham model can be used to describe such fluids. Using the rheological parameters of this model, the water-clay laminar flow friction factors can be determined either by calculating the Reynolds and Hedstrom numbers, or by applying the concept of the extended Reynolds number. A quantitative analysis of the unsteady dam-break type of the free-surface flow is presented, giving a comparison of flow depth profiles and propagation rates between the investigated mixtures and water.

Time-Resolved Shear Viscosity of Wheat Flour Doughs—Effect of Mixing, Shear Rate, and Resting on the Viscosity of Doughs of Different Flours

Abstract: The shear viscosity of three doughs of different wheat cultivars mixed to a farinograph level of 500 BU was measured at low shear rates as a function of the shear deformation using a cone-and-plate viscometer. Cyanoacrylate adhesive was used to attach the dough samples to the instrument surfaces to eliminate wall slip. Flours used were Dragon, Kosack, and a fodder wheat. A distinct difference was observed between the viscosities of the different flour cultivars. The strongest dough (Dragon), with the highest protein content and a good resistance in the farinograph, had the highest maximum viscosity. The doughs showed distinct strain hardening, more pronounced for the strong doughs. Maximum viscosity was obtained at a strain of ≈4, almost independent of the shear rate, but at higher values for stronger doughs (5 for Dragon, 4 for Kosack, and 3.5 for fodder wheat). The maximum was most pronounced for well-mixed doughs after resting. The viscosity and its variation with strain may be used as a measu...

Rheokinetics of curing of epoxy resins near the glass transition

Abstract: The cure of four epoxy-amine systems was studied by viscometry, dynamic mechanical analysis, and DSC. The investigation was carried on at temperatures below and above the glass transition temperature (T g ) of completely cured products. Viscosity growth in the initial stage of cure is described by an exponential-type equation, and on approach to the gel-point by a power law, but the exponent did not coincide with the universal theoretical scaling-law value. A universal viscosity master curve can be constructed if one reduces viscosity and time by their characteristic values. Gel-times and activation energies of curing were found by different methods. It was established that the product of the initial rate of a reaction and the gel-time is constant at various conditions of cure. Time dependences of the degree of conversion (calculated from calorimetric and dynamic mechanical data) in the full range of conversions are described by first- and second-order kinetics, corrected by the factor reflecting self-accelerating character of the reaction. Kinetic constants found from both methods are the same. If a reaction leads to a transition to the glassy state over the course of curing, a self-acceleration equation is valid in the initial stage of the process only. The complete kinetic curve can be described by the DiBenedetto method relating shift of the T g with the degree of conversion. The rate constant for vitrificating systems is presented as a sum of reciprocal values of chemical and diffusion constants. Time and temperature dependences of kinetic and diffusion constants were calculated.

Physical properties of the lithium bromide + 1,3-propanediol + water system

Abstract: The experimental measurements of the basic four physical properties (solubility, vapor pressure, density and viscosity) of the lithium bromide + 1,3-propanediol + water system (LiBr/HO(CH2)3OH mass ratio = 3.5), a possible new working fluid for absorption heat pump, were carried out. Solubility was measured by the visual polythermal method in the temperature range from 264.65 to 358-95 K, and vapor pressure by the boiling point method from 330.75 to 408.45 K. Densities and viscosities were also measured by using a set of hydrometers and Ubbelohde-type capillary viscometers in the temperature range from 283.15 to 343.15 K. Each measured data set was correlated with a proper equation, and all the correlation results showed good agreement between measured and calculated values. Using the correlation results the Duhring chart was constructed and thus the system was found to be able to have a high absorber temperature, which is essential for the design of air-cooled absorption chiller.

Physical properties of the 1980 Mount St. Helens cryptodome magma

Abstract: Physical properties of cryptodome and remelted samples of the Mount St. Helens grey dacite have been measured in the laboratory. The viscosity of cryptodome dacite measured by parallel–plate viscometry ranges from 10.82 to 9.94 log10 η (Pa s) (T=900–982 °C), and shrinkage effects were dilatometrically observed at T>900 °C. The viscosity of remelted dacite samples measured by the micropenetration method is 10.60–9.25 log10 η (Pa s) (T=736–802 °C) and viscosities measured by rotational viscometry are 3.22–1.66 log10 η (Pa s) (T=1298–1594 °C). Comparison of the measured viscosity of cryptodome dacitic samples with the calculated viscosity of corresponding water-bearing melt demonstrates significant deviations between measured and calculated values. This difference reflects a combination of the effect of crystals and vesicles on the viscosity of dacite as well as the insufficient experimental basis for the calculation of crystal-bearing vesicular melt viscosities at low temperature. Assuming that the cryptodome magma of the 18 May 1980 Mount St. Helens eruption was residing at 900 °C with a phenocryst content of 30 vol.%, a vesicularity of 36 vol.% and a bulk water content of 0.6 wt.%, we estimate the magma viscosity to be 1010.8 Pa s.

Using Brookfield data and the Mitschka method to evaluate power law foods

Abstract: Mitschka proposed a simple technique to calculate average shear stress and average shear rate from data obtained with Brookfield viscometers. It allows for estimation of the apparent viscosity, the flow behavior index, and the consistency coefficient of power law fluids. This method was evaluated for typical shearthinning foods (banana puree, salad dressing, enchilada sauce, and pancake syrup) and found to have excellent potential for quality control testing in the food industry. Results compared favorably with those obtained with a standard cone and plate viscometer.

Density, vapor pressure, solubility, and viscosity for water + lithium bromide + lithium nitrate + 1,3-propanediol

Abstract: Four physical properties (solubility, vapor pressure, density, and viscosity) of water + lithium bromide + lithium nitrate + 1,3-propanediol (LiBr/LiNO3 mole ratio = 4, (LiBr + LiNO3)/HO(CH2)3OH mass ratio = 35) were measured The system, a possible working fluid for an absorption heat pump, mainly consists of absorbent (LiBr + LiNO3 + HO(CH2)3OH) and refrigerant (H2O) Solubilities were measured by the visual polythermal method in the temperature range (28555 to 34665) K and in the absorbent concentration range (680 to 750) mass % Vapor pressures were measured by the boiling point method in the temperature range (32535 to 39515) K and in the absorbent concentration range (460 to 696) mass % Densities and viscosities were measured by a set of hydrometers and viscometers, respectively, in the temperature range (28315 to 34315) K and in the absorbent concentration range (243 to 703) mass % The measured values were correlated

Rheo-NMR study of a non-flow-aligning side-chain liquid crystal polymer in nematic solution

Abstract: The flow behavior of a highly concentrated solution of a nematic side-chain liquid crystal polymer in a low molecular mass nematic solvent is investigated by deuterium nuclear magnetic resonance with simultaneous measurement of the shear viscosity in a cone-and-plate NMR viscometer. The director orientation under shear in the magnetic field is determined from the quadrupole splitting of the NMR spectra. The orientation as a function of shear rate is analyzed in terms of the Ericksen-Leslie-Parodi theory, yielding the Leslie coefficients μ 2 and μ 3 and thus the flow alignment parameter λ. From the combined analysis of orientation and viscosity as a function of shear rate a total of four independent viscosity parameters is obtained for the nematic solution. The value determined for the flow-alignment parameter, λ≈0.2, and the analysis of the data based on Brochard's theory show that the polymer is of the non-flow-aligning type and has a slightly prolate shape.

Viscosity of the saturated liquid phase of three fluorinated ethanes: R152a, R143a, and R125

Abstract: Data are reported for the viscosity of three saturated liquids over a temperature range from 255 K to 323 K. The liquids studied are the fluorinated compounds 1,1-difluoroethane (R152a), 1,1,1−trifluoroethane (R143a), and pentafluoroethane (R125). A capillary viscometer constructed of stainless steel and sapphire was used to obtain the data. The viscosity measurements have an expanded uncertainty of 2.4%. A free volume model of viscosity was used to correlate the data.

Viscometric investigation of intramolecular hydrogen bonding cohesional entanglement in extremely dilute aqueous solution of poly vinyl alcohol

Abstract: An investigation of influence of cryogenic treatment on extremely dilute aqueous solution of poly(vinyl alcohol) (PVA) was performed by viscometry. The solution was frozen in liquid nitrogen or in a freezer at −25°C, then thawed at ambient temperature and concentrated by evacuation. The viscosity of the solution was measured using the dilute method. The experimental results indicated that the viscosity of the solution is related to N, the times of the freezing and thawing cycle, and the temperature for freezing. Undergoing a treatment of freezing and thawing, the viscosity of the solution is decreased, while it can be recovered the value of before the treatment as the solution had been heated at a high temperature. Thus, a conclusion may be obtained; that is, for an extremely dilute aqueous solution of PVA, which concentration is below Cgel, threshold concentration for gelation, an intramolecular hydrogen bonding cohesional entanglement can be formed by freezing as N 5, it not only formed an intramolecular hydrogen bonding but also produced an intermolecular hydrogen bonding. At the same time, the abnormal behavior of reduced viscosity of the solution in extremely dilute concentration region has been explained. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2421–2427, 1997

Quantitative Description of the Intrinsic Viscosity of Branched Polyelectrolytes

Abstract: A set of critically cross-linked polystyrenesulfonates with fractal geometry having molecular weights in the range 4.96 × 105 < Mw < 3.07 × 106 was prepared and characterized by viscometry in salt free aqueous solutions. Also these structures show the polyelectrolyte effect, which is a strong increase in reduced viscosity with decreasing concentration. Contrary to that in linear chains, the viscosity below the overlap concentration turned out to be molecular weight independent, which interestingly bridges the behavior between spheres and linear chains. A quantitative evaluation of the data on the basis of a recently decribed model of polyelectrolyte viscosity considering single particle and cooperative multiparticle effects of the charges on viscosity reveals that the complete dependence on polymer concentration is described by assuming only the effective charge number per polymer molecule, Zeff. It is not necessary to assume any concentration-dependent conformational changes.

Micromachined viscosity sensor for real-time polymerization monitoring

Abstract: This paper reports on low-frequency micromachined viscosity sensors intended for real-time polymerization monitoring. The viscosity sensors consist of micromachined membrane resonators featuring electrothermal excitation and piezoresistive detection of transverse membrane vibrations. In contrast to high frequency (above 1 MHz) sensors, e.g. thickness-shear mode sensors or Lamb wave sensors, the use of low-frequency (1-20 kHz) resonators for viscosity sensing, which more closely mimics conventional resonant viscometers, is investigated in this work. The viscous fluid loads the membrane resonator and changes the quality factor of its fundamental resonance. The change in the Q-factor is most pronounced in the viscosity range from 10/sup -3/ Pa/spl middot/s to 1 Pa/spl middot/s.

Viscosity reduction of polymeric liquid by dissolved carbon dioxide

Abstract: The viscosities of polydimethylsiloxane (PDMS)/CO2 solutions were measured over the range of pressures of 1–3 MPa and at the ambient temperature. The viscosities were measured by using a specially designed falling ball viscometer (FBV). The Stokes equation was used to determine the viscosities and the Stokes force expressing the viscous drag of the sphere was corrected for the effect of the lateral cylindrical wall. The Kelley-Bueche (KB) free-volume treatment of the viscosities of polymeric solutions was modified to account for the gas solvent and applied to interpret our data on PDMS/CO2 systems. It was shown that the theoretical equation, based on the assumption of the additivity of free volumes of the components, was capable of predicting with remarkable accuracy the concentration and pressure dependence of the viscosities of the investigated polymeric solutions. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 459–466, 1997

Macroscopic and molecular shear viscosity

Abstract: A brief review of the effect of Newton's macroscopic dynamic shear viscosity on the rotation of a cylinder and a ball in a viscous fluid is presented. The approximate nature of some of Stokes' formulae is discussed, and formulae from elementary viscosity theory are given. The concept of molecular viscosity is introduced, and it is shown that, among other information sources, spectra of depolarized molecular light scattering and electromagnetic wave dispersion in liquids of constant-dipole-moment molecules may, within a certain scheme, be used to derive the value and temperature dependence of the coefficient of shear dynamic molecular viscosity. As an example, the temperature behaviour of molecular viscosity in salol and o-terphenyl is presented and discussed qualitatively.

Cross-linked cationic starches and their use in papermaking

Abstract: A method of making paper comprising the step of adding to a paper furnish, at or prior to the headbox of a paper making machine, a modified starch prepared by swelling a cationised cross-linked starch under conditions selected so that the viscosity of the swollen product is less than 400 cps (measured at 3.0 % w/w starch solids; Brookfield RTV Model viscometer at 70 °C, 100 rpm, No 2 spindle or equivalent). A method of manufacture of a suitably modified starch is also described and claimed.