Viscosity significance

Increases in broth viscosity significantly reduce k a and cause bubble size distributions to become bimodal (30). Overall, k a decreases approximately as the square root of the apparent broth viscosity (31). k a can also be related to temperature by the relationship (32)... 

Other properties of thermoplastics as well. Owing to the relatively low-melt viscosity of thermotropic LCPs, often a small amount of LCP decreases the blend viscosity significantly and renders the matrix thermoplastics easier to process [9-211. 

Lumps can be observed when introducing a stream with a colour and viscosity significantly... 

When a dispersed phase is passed through a nozzle immersed in an immiscible continuous phase, the most important variables influencing the resultant drop size are the velocity of the dispersed phase, viscosity and density of continuous phase, and the density of the dispersed phase (G2, HI, H5, M3, Nl, P5, R3, S5). In general, an increase in continuous-phase viscosity, nozzle diameter, and interfacial tension increases the drop volume, whereas the increase in density difference results in its decrease. However, Null and Johnson (N4) do not find the influence of continuous-phase viscosity significant and exclude this variable from their analysis. Contradictory findings... 

LAMINAR FLOW. A condition of fluid flow in a closed conduit in which the fluid panicles or "streams tend to move parallel to the flow axis and not mix. This behavior is characteristic of low flow rates and high viscosity fluid flows. As the flow rate increases (or viscosity significantly decreasesi. the streams continue to flow parallel until a velocity is reached where the streams waver and suddenly break into a diffused pattern. This point is called the critical velocity. See also Turbulent Flow. 

Similar result brings comparison of power consumption reduction for transport of encapsulated viscous liquid (Russian oil) conveyed by water with conventional pipeline transport of the oil. Transport of viscous oil and oil products by means of capsule pipelining may again provide power consumption reduction from 50% to 70%, the reduction increases with operational velocity. Since for low temperature the oil viscosity significantly increases hydraulic capsule pipeline transport of highly viscous oil and oil products for long distances in arctic conditions can be economically attractive. Capsule pipeline transport could be recommended as suitable transport especially for longer distances when power consumption becomes the most important for operational cost. 

There are variations to the above structure such as fatty acid modification but these tend to increase the viscosity significantly thus limiting use in inkjet ink formulations. 

The diffusion constant is predicted by Eqs. (32) to (35) to be inversely proportional to the total pressure. Experimentally, this is the case to roughly the degree to which the perfect-gas law applies. The equations appear to predict that the diffusion constant will be proportional to the three-halves power of the temperature however, as in the case of viscosity, significant deviations from this behavior occur, as actual molecules are not truly hard spheres and have collision diameters that depend on the relative speeds with which molecules collide with one another. 

The flow condition was measured in a vessel with dished bottom and turbine stirrer or two different axially working stirrers with a two-component LDA [359], which was operated in back-scattering mode, such that the flow field could be averaged over a long period. The measurements were limited to a vertical plane in the middle between two baffles. The liquid viscosity was varied, so that the flow conditions could be measured both in the virtually laminar zone and in the turbulent zone. The internal liquid circulation and the pumping capacity of the stirrers was determined from the velocity measurements. An increase in the viscosity significantly reduced the rate of liquid circulation, as expected. 

Another characteristic viscosity behavior of polyelectrolyte solution, viz., the effect of added salts, has been reported for ionomer solutions [55]. The reduced viscosity of sulfonated PS (Li salt) in DMF increases markedly with decreasing polymer concentration in the absence of added salt, LiCl. However, as the concentration of LiCl increases, the reduced viscosity significantly decreases, then a maximum appears in the viscosity curve, and finally straight lines are obtained. The last behavior is characteristic of neutral polymer solutions. Table 3 summarizes ionomer nonaqueous solutions whose viscosity behavior has been reported. Those results have demonstrated that the viscosity behavior of random ionomers is basically similar to that of polyelectrolyte aqueous solutions. 

What is viscosity Significance at a microscopic level 227 Tab. 8.1. Main fluorescence techniques for the determination of fluidity (from Valeur, 1993)... 

In the previous equation, the viscosity po is measured at low shear and is dependent on temperature and hydrostatic pressure. As mentioned before, the hydrostatic pressure elevates the viscosity, and this should be taken into account. It is estimated that a pressure increase of 700 atmospheres, increases the viscosity by approximately 35%. On the other hand, the major effect appears from the shear conditions which reduce the apparent viscosity significantly. The melt viscosities that prevail here are in the range of lO -lO poise. a is related to the power law (a = 1/n), and its value lies in the range of 4 to 5 (as compared to 1 for a Newtonian liquid). This represents the advantage of shear thinning (pseudoplastic) liquids. An effective viscosity may also be used in the following expression ... 

Large increases in viscosity with monomer conversion. In bulk/solution polymerizations the viscosity at intermediate conversion may approach the limit of what most conventional reactors can handle (20 000-25 000 cP). A very good overview of viscosity increase and its influence on polymerization processes can be found in Moritz [87]. Viscosity significantly affects the polymerization kinetics as well as heat, mass and momentum balances of the polymerization reactor. 

Figure 7. Calcia-alumina-silica system. This illustration compares the melt viscosity of the inviscid binary aluminate melts from 60% CaO to 75% alumina. Addition of MgO and CaO produces quaternary aluminate melts, raises the viscosity significantly and produces a fragile melt with high viscosities below the liquidus temperature and low viscosities above the liquidus temperature. Redrawn from F. T. Wallenberger and S. D. Brown, High modulus glass fibers for new transportation and infrastructure composites and for new infrared uses, Composites Science and Technology, 51.243-263 (1994).

The effect of hydrophobic association on viscosity in the semi-dilute regime is different from that observed at low polymer concentrations. Figure 40, from Bock et al. [89], shows the variation of the reduced viscosity with polymer concentration for polyacrylamide and N-octylacrylamide copolymers having hydrophobe contents of 0.75 and 1 mol%. At a hydrophobe content of 0.75 mol%, the viscosity significantly increased because of intermolecular association. Increasing hydrophobe content further to 1 mol% resulted in higher viscosities. 

Although silanes predominate as adhesion promoters, the use of titanate, zir-conate, and other agents is growing. Titanate adhesion promoters can provide a dual function of improving the dispersion of fillers and enhancing bond performance. Titanates have been used predominantly to modify the viscosity of filled resin systems. A small percentage of titanate in a heavily filled resin system can reduce the viscosity significantly. 

A common example of such a system is ordinary latex paint, containing both polymer latexes and inorganic fillers and pigments, and dispersed in an aqueous phase. The aqueous phase usually contains a dilute solution of polymers capable of associative bonding, that is, bonding weakly with the colloidal solids and/or each other. Such associative bonding increases the viscosity significantly and, more important, contributes a thixotropic nature to the paint see Section 10.5.5. 

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