Viscosity, effect

The drop in pressure when a stream of gas or liquid flows over a surface can be estimated from the given approximate formula if viscosity effects are ignored. The example calculation reveals that, with the sorts of gas flows common in a concentric-tube nebulizer, the liquid (the sample solution) at the end of the innermost tube is subjected to a partial vacuum of about 0.3 atm. This vacuum causes the liquid to lift out of the capillary, where it meets the flowing gas stream and is broken into an aerosol. For cross-flow nebulizers, the vacuum created depends critically on the alignment of the gas and liquid flows but, as a maximum, it can be estimated from the given formula. 

The viscosity of sodium algiaate solutioas is slightly depressed by the additioa of moaovaleat salts. As is frequeatly the case with polyelectrolytes, the polymer ia solutioa coatracts as the ionic strength of the solution is increased. The maximum viscosity effect is obtained at about 0.1 N salt concentration. 

Micellar properties are affected by changes in the environment, eg, temperature, solvents, electrolytes, and solubilized components. These changes include compHcated phase changes, viscosity effects, gel formation, and Hquefication of Hquid crystals. Of the simpler changes, high concentrations of water-soluble alcohols in aqueous solution often dissolve micelles and in nonaqueous solvents addition of water frequendy causes a sharp increase in micellar size. 

It shoiild be noted that the influence of substituting solvents of widely differing viscosities upon the interfacial area a can be very large. One therefore should be cautious about extrapolating data to account for viscosity effects between different solvent systems. 

Rizzuti et al. [Chem. Eng. Sci, 36, 973 (1981)] examined the influence of solvent viscosity upon the effective interfacial area in packed columns and concluded that for the systems studied the effective interfacial area a was proportional to the kinematic viscosity raised to the 0.7 power. Thus, the hydrodynamic behavior of a packed absorber is strongly affected by viscosity effects. Surface-tension effects also are important, as expressed in the work of Onda et al. (see Table 5-28-D). 

Some GPC analysts use totally excluded, rather than totally permeated, flow markers to make flow rate corrections. Most of the previously mentioned requirements for totally permeated flow marker selection still are requirements for a totally excluded flow marker. Coelution effects can often be avoided in this approach. It must be pointed out that species eluting at the excluded volume of a column set are not immune to adsorption problems and may even have variability issues arising from viscosity effects of these necessarily higher molecular weight species from the column. 

The addition of LCP sharply decreased the viscosity of PP in the melt blends, but increased it in the composites. The increase in viscosity effected by the solid LCP fibers was nevertheless surprisingly small. 

Example 3-17 Corrected Performance Curves for Viscosity Effect... 

Calculate Reynolds number, Nr, from Equation 5-8, then correct for viscosity effects. 

At high the power number, P , stays reasonably constant, thus, viscosity has little effect on the power requirements. Wdien moving to lower through the laminar region into the viscous region, the viscosity effect increases. In the laminar range [29]... 

D,-or = Impeller diameter for turbulent regime, corrected for viscosity effect, in. 

There are many interesting reports in the literature where computer simulations have been used to examine not only idealized cases but have also been used in an attempt to explain segregation and viscosity effect in unperturbed polymerization reactors (6). Some experimental work has been reported (7, 8). It is obvious, however, that although there is some change in the MWD with conversion in the batch and tubular reactor cases and that broadening of the MWD occurs as a result of imperfect mixing, there is no effective means available for controlling the MWD of the polymer from unperturbed or steady-state reactors. 

The most comprehensive simulation of a free radical polymerization process in a CSTR is that of Konopnicki and Kuester (15). For a mechanism which includes transfer to both monomer and solvent as well as termination by combination and disproportionation they examined the influence of non-isothermal operation, viscosity effects as well as induced sinuoidal and square-wave forcing functions on initiator feed and jacket temperature on the MWD of the polymer produced. 

Very similar variations in average copolymer composition with conversion have recently been observed in the styrene methyl methacrylate system by both Johnson et al ( and by Dionisio and O Driscoll (. The reason for the variation may be due to a viscosity effect on propagation rate constants QO). 

Several assumptions were made in using the broad MWD standard approach for calibration. With some justification a two parameter equation was used for calibration however the method did not correct or necessarily account for peak speading and viscosity effects. Also, a uniform chain structure was assumed whereas in reality the polymer may be a mixture of branched and linear chains. To accurately evaluate the MWD the polymer chain structure should be defined and hydrolysis effects must be totally eliminated. Work is currently underway in our laboratory to fractionate a low conversion polydlchlorophosphazene to obtain linear polymer standards. The standards will be used in polymer solution and structure studies and for SEC calibration. Finally, the universal calibration theory will be tested and then applied to estimate the extent of branching in other polydlchlorophosphazenes. 

The validity of the above conclusions rests on the reliability of theoretical predictions on excited state barriers as low as 1-2 kcal mol . Of course, this required as accurate an experimental check as possible with reference to both the solvent viscosity effects, completely disregarded by theory, and the dielectric solvent effects. As for the photoisomerization dynamics, the needed information was derived from measurements of fluorescence lifetimes (x) and quantum yields (dielectric constant, where extensive formation of ion pairs may occur [60], the observed photophysical properties are confidently referable to the unperturbed BMPC cation. Figure 6 shows the temperature dependence of the... 

Hand lotions, of the emulsion type, are also, in most cases, oil in water emulsions. A true emulsifying agent is usually used to form the emulsion and for cleansing properties. Vegetable gums, like tragacanth or Irish moss extract, are added, not only to stabilize the emulsion but to increase the emollient properties, because of the added viscosity effect. 

Instead of the Martinelli parameter, Xlt, a convection number, Co, was used for the F factor neglecting the vapor viscosity effects ... 

Similar results were obtained for the decomposition of phenylazotriphenyl-methane however, the lack of viscosity effect on the decomposition of azocumene suggests this process to be concerted. Other reports<9> also indicate symmetrically substituted azo compounds to decompose thermally by a concerted pathway. 

Bulgarevich DS, Kajimoto O, Hara K (1995) High-pressure studies of the viscosity effects on the formation of the twisted intramolecular charge-transfer (TICT) state in 4,4 -diaminodi-phenyl sulfone (DAPS). J Phys Chem 99(36) 13356—13361... 

Besides the thermodynamic properties, viscosity effects also played an important role, as in all commercial blends prepared by a melt process [196]. 

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