Showing papers on "Viscometer published in 1986"

Viscosity-temperature relationships of melts at 1 atm in the system diopside-albite

Abstract: Ansrnlcr The viscosities of six melt compositions have been measured along the join diopsidealbite with a concentric-cylinder viscometer. Measurements were made between 1600 and I 150'C; viscosities were independent of shear rate, indicating Newtonian viscous behavior. Viscosities decreased with increasing temperature and, at constant temperature, they decreased with increasing amounts of diopside component in the mixtures. The temperature dependence ofthe viscosity above the liquidus was fitted to an Arrhenius relationship from which activation eneryies for viscous flow, ranging from 88 kcaVmol for a melt of albite composition to 38 kcal/mol for a melt of diopside composition, were derived. Viscosities over the entire range of the melt and supercooled liquid temperatures were fitted by the method of least squares to the Fulcher equation. Viscosity is strongly dependent upon the mole fractions of silica and alumina and on the number of nonbridging oxygens (NBO/T) in the melt. Addition of diopside to albite melt probably causes a reorganization of the three-dimensional network in favor of a more depolymerized structure. Furthermore, activation energies indicate significant differences in the flow properties ofdiopside versus alumina-bearing melts across the join.

The flow behavior of fiber suspensions in Newtonian fluids and polymer solutions.

Abstract: The main purpose of this study was to examine the viscous and elastic properties and capillary flow of fiber suspensions in Newtonian fluids as well as in polymer solutions. The fillers used were glass, carbon, nylon and vinylon fibers. Glycerin was used as a Newtonian suspending medium and HEC and Separan solutions as viscoelastic suspending media. The viscosity and the first normal-stress difference were measured using a coaxial cylindrical rotating viscometer and a parallel-plate rheogoniometer respectively. The influence of the concentration, aspect ratio, diameter and flexibility of the fibers on the viscous and elastic properties of the fiber suspensions was investigated. Empirical equations were obtained for the relative viscosity and first normal-stress difference for the fiber suspensions in glycerin. The capillary flow of these suspensions is discussed in part II.

Molecular weight distribution of polyphenylene sulfide by high temperature gel permeation chromatography

Abstract: Poly(phenylene sulfide) (PPS) has been characterized using a novel high temperature gel permeation chromatograph (GPC). Samples were injected in slurry form at ambient temperature, and redissolved by an in-line precolumn heater at 250°C. A viscometer consisting of a capillary tube with inlet and outlet taps connected to a sensitive differential pressure transducer was used as sole detector, with deflections converted to concentration using the column calibration. Columns and viscometer were operated at 210°C. Universal calibration was carried out using intrinsic viscosity/molecular weight relations for polystyrene and PPS, determined by light scattering. Satisfactory operation was confirmed by agreement between intrinsic viscosity calculated from GPC with independently measured values, and comparisons with melt flow data. Samples of PPS tested were found to be of relatively narrow distribution, with Mw/Mn typically less than two.

The initial density dependence of the viscosity of organic vapours: Benzene and methanol

Abstract: The paper reports the results of a new investigation of the viscosity of the vapours of benzene and methanol measured in an oscillating-disk viscometer, with small gaps, completely made of quartz. The measurements have been carried out from near room temperature to about 600 K and for densities to 4.3 kg m −3 and 0.055 mol l −1 (benzene) as well as to 1.2 kg m −3 and 0.038 mol l −1 (methanol). The results for benzene have revealed that negative values of the second viscosity virial coefficient B η are not confined to dipolar compounds or helium. Negative values of B η at reduced temperatures (less than 1) seem to represent normal behaviour for all substances. Both the fully modified Enskog theory and as far as possible the theory for the transport properties of moderately dense gases due to Rainwater and Friend have been used for the Lennard-Jones 12-6 potential in order to explain the experimental data.

Transport Properties of Liquids. V. Self Diffusion, Viscosity, and Mass Density of Ellipsoidal Shaped Molecules in the Pure Liquid Phase

Abstract: For ellipsoidal shaped molecules, disk like molecules, and spherical molecules (cycloalkanes, methylcyclosiloxanes, bi- and tricyclic alkanes, carboxylic acids, and aromates) the self diffusion coefficient D, the dynamical viscosity η, and the mass density ϱ were measured (280 ≤ T/K ≤ 360).—Pulsed gradient high resolution 1H NMR spin echo spectroscopy at a field of 4.78 T was applied for the measurements of D(T). η was determined via a Ubbelohde viscosimeter and ρ via a vibrating densitometer.—The free volume theory of Cohen and Turnbull (CT) was extended to molecules of ellipsoidal shape. The extended CT model describes the self diffusion of the 23 compounds examined here in a satisfactory way. Experimental data for D(T), η(T), and ϱ(T) are described in the temperature range studied by appropriate polynomials, too. The activation energies of the transport processes are found from an Arrhenius type Ansatz. They are also discussed on hand of the hybrid equation of Macedo and Litovitz.

High temperature ultrasonic viscometer

Abstract: An ultrasonic viscometer is described which is particularly designed for monitoring the viscosity of a thermally curing resin or composite, such as a fiber-reinforced epoxy composite, in an autoclave at high temperature. According to a preferred embodiment, the viscometer comprises a piezoelectric element of lithium niobate crystals bonded to a first buffer of copper, which is bonded on the other side to a second buffer of aluminum. The resin or composite is in contact with the second buffer. When the transducer emits a short ultrasonic pulse, two echoes are reflected back, the first echo being generated by the copper-aluminum interface, the second by the aluminum-resin interface. The signals from the two echoes are processed to obtain the complex reflection coefficient at the interface of the second buffer and the resin, from which the viscosity of the resin can be calculated and the cure state of the resin determined.

Do anesthetics fluidize membranes

Abstract: The so-called membrane fluidizing effect of anesthetics as a cause of anesthesia has been questioned, mainly because the magnitude of the increase in "fluidity" is insignificant at clinically relevant anesthetic pressures. However, the term "fluidity" has an unfortunate history of being misrepresented in membrane biology. It is often expressed as the ease of movement of probe molecules incorporated into the hydrophobic region of the membrane, thereby representing the property of the microenvironment where the probe molecules reside. In surface chemistry, "membrane fluidity" means inverse viscosity. Membrane viscosity is an integral property of a total membrane (not a part of membrane), and membrane molecules must dislocate and flow against resistance. The ease of motion of probe molecules, therefore, is not fluidity, and is now expressed by the order parameter. The present study measured the effect of halothane on surface viscosity of a phospholipid monolayer spread on a water surface by an oscillating pendulum surface viscometer. The results indicate a significant decrease of about 31% in the surface viscosity by the clinical pressure of halothane; anesthetics do fluidize membranes. Two factors contribute to the surface viscosity of the lipid monolayer; the property of the membrane proper (association between phospholipid molecules) and dragging of water (association between phospholipid and water molecules). The association between phospholipid molecules is in large part related to the order parameter. The fact that anesthetics show little effect on the order parameter, whereas halothane shows a significant effect on the membrane viscosity, indicates that halothane releases surface-bound water. It is postulated that the primary effect of anesthetics on membranes is to weaken the lipid-water interaction forces.

Evaluation of a new dynamic viscometer for measuring the viscosity of whole blood and plasma

Abstract: We evaluated a new type of dynamic viscometer, the Sonoclot Coagulation Analyzer, for use in measuring the viscosity of whole-blood and plasma. Such information can be useful in monitoring patients with hyperviscosity syndromes, e.g., from multiple myeloma. A vibrating Teflon or plastic probe continuously measures dynamic viscosity. The instrument can be calibrated to measure a range of viscosities from 0.69 to 23 cP (mN X s X m-2) or more. The coefficient of variation at 0.69 cP was 3-4% for measurements with the Teflon probe, 7-9% with the plastic probe. Viscosity measured at 37 degrees C for plasma and whole-blood samples from 20 normal patients was 1.22 (SD 0.05) cP and 3.63 (SD 0.52) cP, respectively. Dynamic viscosity measured in blood samples from a single source, with contrived hematocrits ranging from 0 to 89%, increased exponentially as a function of hematocrit, confirming previous studies. Overall, we found this instrument simple and quick to operate, producing accurate, precise viscosity measurements over at least a 40-fold range of viscosity.

The viscosity of argon at high densities

Abstract: The viscosity coefficient of argon has been measured at 174.45 K as a function of pressure from 161 up to 4707 bar, including the melting point at 4637 bar and one data point in the supercooled region. Use was made of a vibrating wire viscometer described in a previous paper. The reduced data have been compared with results obtained from molecular dynamics calculations and the agreement is found to be satisfactory. Following the Batschinski-Hildebrand representation it was found that the present results, as well as earlier reported data measured at higher temperatures, can be described by three different linear relations between the fluidity and the molar volume, corresponding to three adjacent volume ranges, covering half the experimental density range. A further analysis shows that, while at intermediate densities the viscosity may be described by the Enskog formalism, at higher densities the behaviour of η is markedly influenced by correlated motions of the molecules.

Rheological characteristics of selected food gum mixtures in solution

Abstract: The viscosity of pure and mixed dilute solutions of commercial alginate, carrageenan, guar gum, CMC and gelatin solutions at different mixing ratios were measured by a coaxial viscosimeter at different shear rates. The results are presented in the form of measured viscosity divided by the expected viscosity, if no interaction between the gums existed. This technique provides a clear demonstration of the existence of synergism or antagonism between the gums and helps in quantitatively assessing their extent.

Viscosity of binary gaseous mixtures of fluorocarbons.

Abstract: Viscosity of eight binary gaseous mixtures consisting of fluorocarbon refrigerants, namelyR290 mixtures: R290 + R22, R290 + R115, R290 + R502R22 mixtures: R22 + R12, R22 + R13, R22 + R13B1, R22 + R14, R22 + R152ahave been measured at temperatures from 298 to 348 K at atmospheric pressure. The measurements were performed by a rolling-ball viscometer, which was calibrated using nitrogen as a standard gas. The uncertainty of the viscosity data obtained is estimated to be within ± 1.0%. The visocisty of all gaseous mixtures investigated changes almost linearly with composition at constant temperature. The experimental data could be expressed by the empirical Sutherland equation with mean deviation of 0.36 %. It was found that the Chapman-Enskog theory reproduced the experimental data with mean deviations within 1 % except for R290 + R502 mixtures.

Viscometer for low frequency, low shear rate measurements

Abstract: A computer-controlled torsion-oscillator viscometer with low 0.5 Hz frequency and very low 0.05/s shear rate is designed to precisely study shear-sensitive fluids such as microemulsions, gels, polymer solutions and melts, colloidal solutions undergoing coagulation, and liquid mixtures near critical points. The viscosities are obtained from measurements of the logarithmic decrement of an underdriven oscillator. The viscometer is found to have a resolution of 0.2 percent when used with liquid samples and a resolution of 0.4 percent when used with a dense gaseous sample. The design is compatible with submillikelvin temperature control.

A High Pressure Rolling-Ball Viscometer up to 1 GPa

Abstract: A rolling-ball viscometer has been developed for use under high pressures up to 1 GPa. It is proven that the calibration coefficient of the viscometer depends on its inclination angle and that this dependence varies with the diameter ratio of the ball and tube. In order to permit a simultaneous measurement of the density, the viscometer was improved, allowing for the attachment of a potentiometric displacement sensor. The precision of the density measurement is estimated to be ±0.22%. The viscosity data of a pressure-transmitting liquid, di-(2-ethyl-hexyl) sebacate (Univis P12), is presented in the range of pressures up to 800 MPa at temperatures from 6 to 60°C. The accuracy of a viscosity measurement is estimated to be ±0.95%.

Interpretation of screen factor measurements.

Abstract: Screen-factor (SF) measurements are widely used in the petroleum industry to characterize polymer solutions. The measurements are easy to perform and provide information that is different from solution-viscosity measurements. However, there has been no quantitative explanation of what solution property is being measured by SF. The authors show that SF measures the elongational viscosity of a polymer solution. Experiments on a modified commercial screen viscometer show the relationship between SF measurements and elongational-flow measurements performed by Durst and coworkers. Durst has shown that the elongational flow field in a packed bed of spheres triggers a transition in the conformation of a flexible polymer molecule, such as polyacrylamide, from a coiled to a stretched state. This transition in conformation is accompanied by a jump in the resistance to flow by an order of magnitude. They show that conventional screen viscometers operate in the regime where the molecules are in the highly stretched state. On the basis of Durst's work, it is calculated that the SF measurement is sensitive to high-molecular-weight tails in the polymer molecular-weight distribution.

An Analytical Model to Predict the Effects of Heating Rate and Applied Load on Glass Transition Temperatures of Dental Porcelain

Abstract: An analytical model was developed to predict the effects of heating rate and load on the glass transition temperature (Tg) of dental porcelain. An equation similar to the Moynihan equation relating heating rate to Tg was found for midspan load. The validity of the analytical model was demonstrated by using viscosity data from one published study to predict Tg behavior in an independent study. Values of Tg calculated with the analytical model for a dilatometer specimen were found to be higher than Tg values calculated for a bending beam viscometer.

A mechanism for non‐newtonian flow of milk in a capillary

Abstract: The apparent viscosity of human milk, fresh cow's milk, homogenized milk, skim milk and oleic acid emulsion have been determined in a Maron-Belner type low shear capillary viscometer using capillaries of different radii combined with a photomicroscope. Photomicrographs of the flowing fluids have been obtained and analyzed by a densitometer. Each suspension examined showed different apparent viscosities and the viscosities depended also on capillary radius. This capillary radius effect was traced to migration of milk fat droplets during flow through the capillary. By assuming that the wall layer is composed of double layers in a flowing liquid in a capillary tube this radius effect may be attributed to geometric hindrance of the capillary wall against the thermal motion of fat droplets near the wall, Values of the wall thickness were calculated.

Application of a modified rotary rheometer to the investigation of slurries

Abstract: A new technique for investigating some of the rheological properties of slurries is proposed. A commercial concentric cylinder viscometer was modified so that a continuous coaxial flow could be superimposed on the Couette flow; this eliminated the influence of sedimentation of the solid particles. The influence of the changed strain was measured and found to be small. Relations between the shear stress and shear rate, temperature, mass fraction of solids and particle size were determined for a coal-oil slurry. The power-law coefficients were calculated. The influence of solid particles on the power-law coefficientskm andnm was determined and approximated by empirical equations.

Low-toxicity oil muds: A knowledge of downhole rheological behavior assists successful field application

Abstract: The introduction of oil-based drilling fluids has led to significant improvements in drilling efficiency for many North Sea operations. The original formulations that were based on diesel are generally being replaced by the lower-toxicity mineral oils. One factor crucial to the successful application of mineral oils has been a knowledge of their downhole rheological characteristics. This paper describes a purpose-built viscometer capable of simulating realistic downhole temperature (300/sup 0/C (572/sup 0/F)) and pressure (100 MPa (1,000bar)) conditions. Results from this study are used to indicate how surface-fluid rheologies can be tailored to provide adequate downhole viscosities, thus reducing total system pressure losses.

Turbine flow meter viscosity control

Abstract: A viscosity control (10, 200) is disclosed which employs a turbine flow meter (52). A pump (18) provides for a flow of solution through a conduit at a relatively constant pressure. The flow rate of the solution through the conduit thus varies depending on the viscosity of the solution. The turbine of the flow meter rotates at an angular velocity related to the flow rate. The rotational velocity of the turbine is sensed. When the turbine speed decreases as viscosity increases to a set maximum viscosity, the control supplies solvent to the solution to decrease the viscosity.

Rheological characteristics of magnetic fluids.

Abstract: Study of the rheological property of water, hydrocarbon and diester based magnetic fluids is done with and without magnetic field. Experimental study is made using the concentric cylinder type rotating viscometer which is operated within the strong magnetic field to clarify the effects of magnetic field, temperature and shear rate on thee rheological characteristics of the magnetic fluids. The above magnetic fluids are Newtonian in the case of no magnetic field. In the case of applied magnetic field, the observed flow curve for hydrocarbon based fluid is still Newtonian. On the otherhand, the water based and diester based fluids show pesudoplastic behaviour. Empirical formulae based on the theoretical consideration of the laminar flow between rotating concentric cylinders are obtained.

A rolling ball viscometer for high pressure use

Abstract: A rolling ball viscometer has been developed for use at high pressures up to 1 GPa. It is proved that the calibration coefficient of the viscometer depends on its inclination angle and this dependence varies with the diameter ratio of the ball and tube. Improvement is made in order to allow simultaneous measurement of the density by assembling a potentiometric displacement meter. The precision of the density measurement is estimated to be ±0.22%. The viscosity data of di-(2-ethyl-hexyl) sebacate (Univis P12) is presented in the range of pressures up to 800 MPa at temperatures from 6 to 60°C. The accuracy of the viscosity measurement is estimated to be ±0.95%.

Use of a sequential extraction technique to determine the MWD of bulk UHMWPE

Abstract: The molecular weight distribution (MWD) of bulk ultrahigh molecular weight polyethylene (UHMWPE) was determined by an increasing temperature sequential extraction technique. Using decahydronapthalene (decalin) as the solvent, 5 g samples of UHMWPE were fractionated stepwise from room temperature to 190°C in 10°C increments. Results via high temperature capillary viscometry show that intrinsic viscosity ([η]) ranges from 12.0 to 37.0 dL/g or that the viscosity average molecular weight (Mv) ranges from approximately 1.6 to 7.4 × 106. When the integral distribution is plotted against Mv on logarithmic probability graph paper, a straight line (i.e., a Wesslau distribution) results. Although the present methodology is tedious, many previous problems which have led to degradation are overcome by this technique.