Dilatant properties

Dilatant Property of a fluid whose apparent viscosity increases with increasing shear rate. 

Faergemand, M., Murray, B.S. (1998). Interfacial dilatational properties of milk proteins cross-linked by transglutaminase. Journal of Agricultural and Food Chemistry, 46, 884-890. 

The results of the latest research into helical flow of viscoplastic fluids (media characterized by ultimate stress or yield point ) have been systematized and reported most comprehensively in a recent preprint by Z. P. Schulman, V. N. Zad-vornyh, A. I. Litvinov 15). The authors have obtained a closed system of equations independent of a specific type of rheological model of the viscoplastic medium. The equations are represented in a criterion form and permit the calculation of the required characteristics of the helical flow of a specific fluid. For example, calculations have been performed with respect to generalized Schulman s model16) which represents adequately the behavior of various paint compoditions, drilling fluids, pulps, food masses, cement and clay suspensions and a number of other non-Newtonian media characterized by both pseudoplastic and dilatant properties. 

In another test method (ASTM D-5515), a dilatometer is used to measure the swelling of bituminous coal. The test method is limited in applicability to coal that has a free swelling index < 1 (ASTM D-720). The principle of this test method is that the final volume of char obtained at the conclusion of a standard dilatation test is dependent on the mass of coal in the coal pencil and on the radius of the retort tube. This test method incorporates a procedure that determines the mass of air-dried coal in the coal pencil, provides a means to measure the average retort tube radii and employs a means to report coal expansion on an air-dried coal weight basis. The value of the dilatation properties of coals may be used to predict or explain the behavior of a coal or blends during carbonization or in other processes, such as gasification and combustion. 

J. Lucassen, Capillary forces between solid particles in fluid interfaces, Colloids Surf. 65, 131-137 (1992) Dynamic dilational properties of composite surfaces, Colloids Surf. 65, 139-149 (1992). 

The title theophylline isotopomers 28 and 29, 2,6-dihydro- 1,3-dimethylpurines, are alkaloids known for their diuretic, cardiotonic and coronary-dilating properties, and are used at present in therapeutics as a bronchodilators in all kinds of asthma12. They have... 

A large variety of techniques for measuring interfacial rheological parameters exists. A first classification can be made between techniques suited for measuring interfacial shear and interfacial dilational properties. A recent review of the various techniques can be found in a review by Miller et ah ). In order to prevent undue fragmentation of the text, here we shall also describe techniques that work better for Gibbs monolayers. 

A number of compounds have been reported which have coronary dilator properties or other activities which have culminated in their clinical trial for use in angina pectoris. Lidoflazlne (IV) is claimed to be a specific, long acting coronary vasodilator. This agent appears to reduce coronary vascular resistance in dogs and causes an Increase in coronary venous pO. ... 

As for pure LMWE films, the surface dilatational modulus is higher for protein-saturated-LMWE than for protein-unsaturated-LMWE mixed films at every surface pressure. The surface dilatational properties of mixed protein-emulsifier films also depend on the presence of some food components (ethanol and sucrose) in the aqueous phase. In general, a decrease in the dilatational rheological properties on the addition of ethanol was found for protein-water-insoluble LMWE. That is, the static and... 

Polymer solutions and melts, residual oils, rubber solutions, many petroleum products, paper pulps, biological fluids (blood, plasma), pharmaceutical compounds (emulsions, creams, and pastes), various food products (fats and sour cream) can serve as examples of pseudoplastic fluids. Dilatant properties are mainly exhibited by high-concentration or coarse-disperse systems (such as... 

Surface dilatational properties tend to differ considerably between amphiphiles and polymers, partly because the surface equation of state is different. From Eqs. (10.22) and (10.23) it follows that if (a) t is short or S is thin and (b) dc/dr is small (which is true if T is small), ESD x dTl/d In 7. Figure 10.36 gives 17 versus In F, and the slopes of the curves will thus roughly give ESD. It is seen that SDS will give a substantial modulus at far smaller 7 values (in mg m 2) than the proteins do. This is a general trend. 

Surface dilatational properties are essential in several phenomena of practical importance, because these determine what y will be at fast... 

These results should be viewed with caution. In the first place, they concern a single film, not a foam, and can therefore only give trends. Secondly, we have assumed the film surfaces to be immobile, which would imply that the surface dilational properties are completely elastic. This is rarely the case, especially if it concerns small-molecule surfactants. Consequently, some slip will occur at the film surfaces, and drainage will be faster than that of Eq. (11.4). As discussed in Section 10.8.3, several... 

Surface Dilational Properties. The calculations just given suggest that all foam will rapidly disappear, but several foams can be fairly persistent, and some can hardly be destroyed. Stabilization to Ostwald ripening (or to disproportionation as foam researchers usually call it) is thus possible. 

Dynamic Surface Tension and Surface Dilational Properties of an Amphiphilic Polysaccharide... 

Dynamic properties of interfaces have attracted attention for many years because they help in understanding the behaviour of polymer, surfactant or mixed adsorption layers.6 In particular, interfacial rheology (dilational properties) is crucial for many technological processes (emulsions, flotation, foaming, etc).1 The present work deals with the adsorption of MeC at the air-water interface. Because of its amphiphilic character MeC is able to adsorb at the liquid interface thus lowering the surface tension. Our aim is to quantify how surface active this polymer is, and to determine the rheological properties of the layer. A qualitative and quantitative evaluation of the adsorption process and the dilata-tional surface properties have been realised by dynamic interface tension measurements using a drop tensiometer and an axisymmetric drop shape analysis. 

There is a lack of systematic experimental studies. Only on the basis of a large data base can further improvements in the theories be made. Thus, the more effective instruments and newly developed techniques should enable surface scientists to produce more systematic data. There is also a deficiency in respect to relaxation theories for polymers and mixed polymer/surfactant systems. First ideas about dilational properties of composite adsorption layers were published by Lucassen (1992). A theory has also been developed by Johnson Stebe (1994) to differentiate exchange of matter from dilational viscosity. This calls for new experimental developments. 

Irregularities in dynamic surface tensions of adsorption layers of soluble surfactants were discussed by Lucassen-Reynders (1987) in terms of aggregation phenomena of adsorbed molecules. She gave a theoretical model for the frequency spectrum of surface dilational properties. 

The first term is a geometric component only controlled by the capillary size and the interfacial tension of the pure system. The second term is used to calculate the dilational properties. Ay as the change in interfacial tension also incorporates the elastic and viscous contributions. The third term in Eq. (4.129) is controlled by hydrodynamic effects. For example, at higher frequencies inertia effects must be considered. To maintain the experimental accuracy it is important to retain the hemispherical form of the droplet. 

Many experiments have been proposed for measuring the interfacial shear viscosity and elasticity and interfacial dilatational viscosity and elasticity at gas/liquid and liquid/ liquid interfaces [22]. Interfacial shear viscosities of different oil/aqueous systems have been studied worldwide. Some experimental results indicate that low interfacial shear viscosities do not necessarily imply that an emulsion will be unstable [23]. The dilatational rheology is based on area changes due to an expansion or compression of a fluid surface and stress relaxation experiments. The experiment results show that the interfacial dilatational properties can be much higher than the interfacial shear properties for the same system [15,24-27]. This makes researchers believe that interfacial dilatational viscosity and elasticity may have a better relationship with the stability of the emulsion than with interfacial shear properties. 

Tolperisone is an arylalkyl p-aminoketone having an asymmetric carbon atom a to the carbonyl group. The R(—)-enantiomer is a centrally acting muscle relaxant used in the treatment of spastic paralysis, whereas the S(+)-enantiomer shows broncho and peripheral dilating properties. 

Galileo is credited with inventing the first instrument to assess the change in temperature, referred to as a thermoscope. Thermoscopes show changes in temperature but lack a quantitative scale. Jean Rey in 1632 was the first to use the dilation properties of liquids. In 1641, Ferdinand II, Grand Duke of Tuscany, hermetically sealed alcohol in a glass contraption with graduation marks. 

Mechanical-based instruments used to measure temperature are based on the dilation properties of gases, liquids, and solids. The first thermometers were based on gases. The volume of an ideal gas will change in direct proportion to its temperature (under isobaric conditions). According to Charles Law ... 

Liquid thermometers are the most common instrument employed to measure atmospheric temperature. They have an excellent range and can measure temperatures from as low as -200 °C to above 600 C. Similarly to gas thermometers, they are based on the dilation properties of liquids when subject to changes in temperature. Many liquids have been used to measure temperature including water, alcohols, mercury, paraffins, and aromatics. 

Characteristic of polymer PM makes that the polyurethane mass works as a material of good dilatation properties. During winter, the polymer limits joints (cracks) expansion in opposite to bituminous mass, which does not work (displacement in case of polymer is 3-5 times lower [12]). During summer, the polymer allows for compression in its volume and free closing of a joint without squeezing filling mass out, as it occurs in the case of bituminous mass, see Fig. 17. 

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