Quasi-Newtonian viscosity

According to the structure of this equation the quantity cp indicates the influence of the filler on yield stress, and t r on Newtonian (more exactly, quasi-Newtonian due to yield stress) viscosity. Both these dependences Y(cp) andr r(cp) were discussed above. Non-Newtonian behavior of the dispersion medium in (10) is reflected through characteristic time of relaxation X, i.e. in the absence of a filler the flow curve of a melt is described by the formula ... 

These data show clearly that that the intrinsic behavior in pure metals is visco-elastic with the velocity proportional to the applied stress (Newtonian viscosity). Although there is a large literature that speaks of a quasi-static Peierls-Nabarro stress, this is a fiction, probably resulting from studying of insufficiently pure metals. 

We have measured by quasi-elastic light scattering the hydro-dynamic radius of PEO s samples in 2 solvents water and water-isopropanol mixture (90%/10%) as a function of the age of the solutions. We study the influence of the solvent on the properties of the 2 higher molecular weight samples (WSR 301 and Coagulant) in laminar (non-newtonian viscosity) and turbulent (drag reduction) flow conditions. 

In the case reported above, the viscosity anomaly in the region of isotropic solutions was not taken into consideration. However, if we plot both branches for different shear stresses, it is possible to obtain the following. The viscosity increases sharply for c > c with stress Xj, corresponding to segment I of the flow curve (Fig. 9.20, curve 1). For stress Xjj (quasi-Newtonian branch), the dependence t](c) is of the usual nature for LC solutions. For stress Xjn corresponding to region III of the flow curve, the viscosity has no maximum or even a break at c, but monotonically increases with an increase in c. Although curves 1 and 2 practically require no explanation, destruction of the LC structure... 

The dependence of the heat of activation of flow on the concentration of copolymer based on PPTA in sulfuric acid is shown in Fig. 9.25. An increase in the steepness in the pretransition region and a sharp decrease in for c> c are characteristic of this dependence. The value of E decreases by approximately 3 times in the range of concentrations of =1% in the region of the transition from the isotropic to the LC state. Not only the heat of activation but also generally the temperature dependence of the viscosity are the same for different concentrations for LC solutions. This can indicate the preservation of the same kinetic unit of flow on the segment of quasi-Newtonian flow (at the limit the molecule or segment), which is characteristic of systems with a continuous LC phase. 

Corcione et al. [128] used a combination of organically modified boehmite and hyper-branched polymer HBP, with the aim of modifying the reactivity of the epoxy matrix. The presence of the HBP increased the reactivity which leading to increased viscosity and a quasi-Newtonian behavior was observed at a relatively high shear rate. This observation was made irrespective of the HBP composition. 

Substances which exhibit anomalous viscosity have been called quasi-viscous. Other designations, in which attempts are made to characterize and in part explain anomalous viscosity, have been used. They are variable viscosity, structural viscosity (61), and plasticity. Of these expressions, plasticity is the most unfortunate for it is precisely a lack of plasticity which characterizes non-Newtonian sols and gels. It is confusing and mi.s-leading to redefine a familiar term. Certain chemists such as Guth (31) use plasticity in its older and correct connotation. 

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