Esters shear viscosity

The surface shear viscosity of a monolayer is a valuable tool in that it reflects the intermolecular associations within the film at a given thermodynamic state as defined by the surface pressure and average molecular area. These data may be Used in conjunction with II/A isotherms and thermodynamic analyses of equilibrium spreading to determine the phase of a monolayer at a given surface pressure. This has been demonstrated in the shear viscosities of long-chain fatty acids, esters, amides, and amines (Jarvis, 1965). In addition,... 

Fig. 25 Surface shear viscosity vs. film composition for the palmitic acid/stearoylserine methyl ester film system at 25°C.

An unusually extensive battery of experimental techniques was brought to bear on these comparisons of enantiomers with their racemic mixtures and of diastereomers with each other. A very sensitive Langmuir trough was constructed for the project, with temperature control from 15 to 40°C. In addition to the familiar force/area isotherms, which were used to compare all systems, measurements of surface potentials, surface shear viscosities, and dynamic suface tensions (for hysteresis only) were made on several systems with specially designed apparatus. Several microscopic techniques, epi-fluorescence optical microscopy, scanning tunneling microscopy, and electron microscopy, were applied to films of stearoylserine methyl ester, the most extensively investigated surfactant. 

Figure 1 shows the frequency dependence of the absolute value of the conplex viscosity T) for EMA-Zn-0 and EMA-Zn-40 as conpared to EMA-Zn-20. It can be seen in this figure that the zero shear viscosity T) is asymptotically approached for all the EMA-salt and EMA samples. This result is consistent with the observation of Earnest, MacKnight et al. (18,20-21) who have shown that the zero-shear viscosity is asymptotically approached for EMA and its methyl ester however, it is not for its 70% neutralized sodium salt, which is not inconsistent with the fact that the largest salt content of Fig. 1 is 40%. 

Figure 11.2a shows that the low frequency limit of dynamic viscosity is very similar to the low shear limit of steady shear viscosity throughout the concentration sequence of isotropic to biphasic to anisotropic. At higher frequencies the dynamic viscosity peak is reduced in magnitude [24] for lyotropic cellulose esters + DMAC, just as viscosity is reduced at higher shear rates (Figure 11.2b). However the concentration of the peak was reported not to decrease with frequency. Thus it appears that dynamic shear, unlike steady shear, does not drive the thermodynamic transition for formation of an anisotropic phase to a lower concentration.

For liquid crystal displays, mixtures of liquid crystals are always used. Therefore, there is an essential interest in models that predict the rotational viscosity of mixtures from the rotational viscosities of the pure components. With the exception of mixtures of very similar compounds, the dependence of the shear viscosity of isotropic liquids on the mixture composition is normally complex. Due to the additional dependence on the order parameter, one cannot expect a simple concentration dependence for the rotational viscosity of liquid crystals. Figure 20 shows the rotational viscosities of a series of mixtures between the ester LCl... 

Viscosity is defined as the shear stress per unit area at any point in a confined fluid divided by the velocity gradient in the direc tiou perpendicular to the direction of flow. If this ratio is constant with time at a given temperature and pressure for any species, the fluid is caUed a Newtonian fluid. This section is limited to Newtonian fluids, which include all gases and most uoupolymeric liquids and their mixtures. Most polymers, pastes, slurries, waxy oils, and some silicate esters are examples of uou-Newtouiau fluids. 

Dynamit-Nobel AG, NethP, Appl 6411854 (1966) CA 65, 6992(1966) (Liquid esters of nitric acid and aromatic nitro compds can be gelatinized with polymers of unsatd acids or unsatd alcohols and their derivs. The advantages of these polymers include increased safety of manipulation and increased rate of gelatinizacioii. Thus a 60/40—NG/ NGc soin was mixed with 3 wt %-of finely powd polymethylacrylates and, after 1.5 hrs, had a viscosity of 4250 cp at 20° under shearing gradient of 15 sec )... 

Fatty acids were not discussed in the US patents or literature for the purpose of forming nanoemulsions, but they were included in the study for comparative purposes and because of their low viscosities compared to ester-oils that consist of three fatty acids molecules per oil molecule. The lower viscosity liquids are easier to shear in a homogenizer... 

The stability of these products is governed not only by their composition but also by mechanical factors. The finished product is shear sensitive. From a formulation standpoint, usual actives do not enable the production of storage-stable concentrated products without incorporating emulsifiers such as fatty esters, ethoxylated fatty amines, or amides, and the viscosity must be further adjusted using inorganic salts. Moreover, the formulation of concentrates requires alcohol-reduced grades... 

The particular orientation of the LCP in the course of flow effects a shear thinning at low shear rates. High shear forces favor the formation of fibrils. In aromatic poly(ester)/LCP blends, the viscosity ratio is more responsive in controlling the morphology." ... 

EVOLUTION OF THE VISCOSITY COEFFICIENT OF SHEARING OF THE GLYCEROL AND ITS ESTERS WITH ACETIC ACID AS A FUNCTION OF PRESSURE. 

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