Solutions, pure, viscosity measurement

Once the constant-temperature water bath has reached 30°C, measuring the viscosities of pure solutions like standard oils requires 15 min per sample. The most time-consuming part of the measurement is cleaning and drying the viscometer between samples. Preparing fruit pastes and juices for viscosity determination will take 1 hr for two to four different samples and then an additional -15 min/sample for the viscosity measurements. 

Viscosity measurements on emulsions were carried out with three types of viscometers. Figure 2 shows the flow curves of emulsions with different volume ratios of the two solutions, as measured with a Ferranti-Shirley cone-plate viscometer. The ratio between the viscosities of the two pure polymer solutions is about 3 at low shear rates but only 2 at the highest shear rates. 

Another very useful approach to molar mass information of complex polymers is the coupling of SEC to a viscosity detector [55-60]. The viscosity of a polymer solution is closely related to the molar mass (and architecture) of the polymer molecules. The product of polymer intrinsic viscosity [r ] times molar mass is proportional to the size of the polymer molecule (the hydrodynamic volume). Viscosity measurements in SEC can be performed by measuring the pressure drop AP across a capillary, which is proportional to the viscosity r of the flowing liquid (the viscosity of the pure mobile phase is denoted as r 0). The relevant parameter [r ] is defined as the limiting value of the ratio of specific viscosity (qsp= (n-noVflo) and concentration c for c—> 0 ... 

A characteristic feature of a dilute polymer solution is that its viscosity is considerably higher than that of either the pure solvent or similarly dilute solutions of small molecules. The magnitude of the viscosity increase is related to the dimensions of the polymer molecules and to the polymer-solvent interactions. Viscosity measurements thus provide a simple means of determining polymer molecular dimensions and thermodynamic parameters of interactions between polymer and solvents. These aspects will also be considered in a later part of this chapter. 

The viscosity of a liquid or solution can be measured by using a viscometer whose design is based on the Hagen-Poiseuille law. Essentially, this involves the measurement of the flow rate of the liquid through a capillary tube which is part of the viscometer. Consequently, by measuring the flow time of the solution, t, and that of the pure solvent, to, the relative viscosity can be determined ... 

Physico-chemical behaviour in aqueous solution was studied by viscosity measurements. Expected associative behaviour has been evidenced in pure water, while in salt media, the associative behaviour strongly depends on PCL chains length. For shorter PCL chains, intramolecular hydrophobic interactions are predominant, even in the semi-dilute regime. This non-classical behaviour for an associative polyelectrolyte opens the way to the conception of amphiphilic matrices with hydrophobic clusters for controlled release applications. 

Viscosity measurements were performed before each set of two-phase experiments to estimate the actual viscosity values of the ionic liquids. Although the ionic liquids used in this research are hydrophobic, they still absorb small amounts of water (hygroscopic) depending on the initial nitric acid concentration in the aqueous phase. The absorbed water is expected to affect their viscosity (Billard et al. 2011b). To estimate the viscosity of the saturated ionic liquid, prior to the experiments the ionic liquids were stirred with water or nitric acid solutions. Saturation was confirmed, when the viscosity did not change over time. The viscosities of the ionic liquids were measured using a digital Rheometer DV-III Ultra (Brookfield) at room temperature and were found to decrease by 15-20 % when saturated with aqueous phase compared to the values of pure ionic liquids. 

The glass transition temperature of the pure solvent 7 (0), obtained by extrapolation (m -> 0), is found to be independent of the solutes in a given solvent and equal to that from viscosity measurements, which shows that the glass transition temperature is the appropriate reference temperature for transport processes in the liquid state. Using this result in Eq. (82) yields the further important... 

The viscosity of the membrane solution in the pores of the support, cannot be measured. Here, the viscosities of amine solutions saturated with pure (ZO2 at latm were measured with an Ostwalds viscometer and these values were taken as the viscosities of the membrane solutions. The viscosities are listed in Table III. This... 

One of the easiest means of determining the molar mass of a polymer is via viscometry. This yields the viscosity average molar mass, Mt . The viscosity of a polymer solution can be measured using capillary viscometers. The time for flow of the polymer solution through a given distance is measured and this is proportional to viscosity. The viscosity obtained by this method is expressed relative to that of the pure solvent. To determine molar mass, the intrinsic viscosity is required. It has this name because it relates to the intrinsic ability of a polymer to increase the viscosity of a solvent. The intrinsic viscosity [ j] is related to the specific viscosity jsp = 1 — rj/rjo, where rj is the viscosity of the polymer solution and rjo is that of the solvent via a virial equation in concentration resembling Eq. (2.9). It has been found empirically that for many polymer solutions the Mark-Houwink equation for intrinsic viscosity is obeyed ... 

The introduction of the coefficient of viscosity measured by flow in the case where the particle moves in a pure liquid has been experimentally justified by Svedberg and Eriksson-Quensel (1936), who showed that the same sedimentation constant of Helix hemocyanin is obtained in mixtures of heavy and ordinary water in various proportions if corrections for density and viscosity are introduced. In the cases where the solvent is a dilute electrolyte solution, the necessity of a correction for the increased viscosity has not been completely proved. The corrections which are applied are in most cases sufficiently small to fall within the error of the determinations since for solutions of buffer below half-molar concentration the ratio i7bu o-/> watei does not exceed unity by more than 5%. 

Equations (83) and (84) provide a molecular interpretation of the thermoelastic data through equation (89). This equation establishes the relationship between the purely thermodynamic quantity f /f and its molecular counterpart of dlno/dT, which can be interpreted in terms of the rotational isomeric state theory of chain configurations. It permits comparison of the change of the unperturbed dimensions o obtained by thermoelastic measurements on polymer chains in the bulk (in network structures) with that obtained by viscosity measurements on chains of the same polymer, essentially isolated in dilute solution. 

Traditional dielectric analysis of highly resistive materials, such as ceramics, plastics, polymers, and colloids, is frequently more concerned with purely bulk-material effects and often relies on non-electrochemical analysis methods, such as modulation of the sample temperature (Chapter 1). In addition, the temperature effects on bulk-solution conductivity values must be considered in any experimental setup. Most referenced solution conductivities are measured and reported at room temperature, and for a standard laboratory aqueous-solution analysis this information is appropriate to consider as the first approximation. However, the bulk-solution conductivity a of aqueous media increases at 2% per degree °C as the result of decrease in viscosity of water with increase in the temperature [1, p. 17]. 

It was made clear in Chapter II that the surface tension is a definite and accurately measurable property of the interface between two liquid phases. Moreover, its value is very rapidly established in pure substances of ordinary viscosity dynamic methods indicate that a normal surface tension is established within a millisecond and probably sooner [1], In this chapter it is thus appropriate to discuss the thermodynamic basis for surface tension and to develop equations for the surface tension of single- and multiple-component systems. We begin with thermodynamics and structure of single-component interfaces and expand our discussion to solutions in Sections III-4 and III-5. 

Anotlier simple way to obtain the molecular weight consists of measuring tire viscosity of a dilute polymer solution. The intrinsic viscosity [q] is defined as tire excess viscosity of tire solution compared to tliat of tire pure solvent at tire vanishing weight concentration of tire polymer [40] ... 

The viscosity ratio or relative viscosity, Tj p is the ratio of the viscosity of the polymer solution to the viscosity of the pure solvent. In capillary viscometer measurements, the relative viscosity (dimensionless) is the ratio of the flow time for the solution t to the flow time for the solvent /q (Table 2). The specific (sp) viscosity (dimensionless) is also defined in Table 2, as is the viscosity number or reduced (red) viscosity, which has the units of cubic meters per kilogram (m /kg) or deciUters per gram (dL/g). The logarithmic viscosity number or inherent (inh) viscosity likewise has the units m /kg or dL/g. For Tj g and Tj p, the concentration of polymer, is expressed in convenient units, traditionally g/100 cm but kg/m in SI units. The viscosity number and logarithmic viscosity number vary with concentration, but each can be extrapolated (Fig. 9) to zero concentration to give the limiting viscosity number (intrinsic viscosity) (Table 2). 

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