Viscosity compositional dependence

At low concentration of the second polymer, blends have dispersed-phase morphology of a matrix and dispersed second phase. As the concentration increases, at the percolation threshold volume fraction of the dispersed pase, ([) = 0.16, the blends structure changes into co-continuous. Full co-continuity is achieved at the phase inversion concentration, ( ). The morphology as well as the level of stress leads to different viscosity-composition dependencies (for more details see Chapter 7. The Rheology of Polymer Alloys and Blends ). 

While Eq. (2.33) is valid for monodispersedathermal polymers, in reality polymers are polydispersed and do interact with each other. Consequently, application of the model to a real system requires that the influence of individual molecular weight fractions on the rheological functions is taken into account. For example, in the simplest case of the zero-shear viscosity-composition dependence for entangled systems [194, 195] the prediction is ... 

Polymer solution viscosity is dependent on the concentration of the solvent, the molecular weight of the polymer, the polymer composition, the solvent composition, and the temperature. More extensive information on the properties of polymer solutions may be found ia refereaces 9 and 54—56. 

Concentrated, Binary Mixtures of Nonelectrolytes Several correlations that predict the composition dependence of Dab. re summarized in Table 5-19. Most are based on known values of D°g and Dba- In fact, a rule of thumb states that, for many binary systems, D°g and Dba bound the Dab vs. Xa cuiwe. CuUinan s equation predicts dif-fusivities even in hen of values at infinite dilution, but requires accurate density, viscosity, and activity coefficient data. 

Knowing how ion conduction is determined by the interplay between the dielectric constant and viscosity, the dependence of ion conductivity on different variables that are of practical interest can be explained consistently. Extensive studies have been carried out on the effects of salt concentration, solvent composition, and temperature on ion conductivity in... 

Composition Dependence of Alloy Viscosity. Attempts have been made to calcnlate the viscosity of a dilnte liquid alloy from a theoretical standpoint, but with little success. This is primarily due to the fact that little is known about the interaction of dissimilar atoms in the liquid state. Empirical relationships for the viscosity of dilute liquid alloys have been developed, but these are generally limited to specific alloy systems—for example, mercury alloys with less than 1% impurities. The viscosities of binary liquid alloys have been empirically described using a quantity called the excess viscosity, (not to be confused with the excess chemical potential), which is defined as the difference between the viscosity of the binary mixture (alloy), pa, and the weighted contributions of each component, xipi and X2P2-... 

Fig. 12. The relative viscosity of polyacrylamide-co-acrylates versus different copolymer compositions depending on the presence of the low-molecular-weight electrolyte sodium sulfate. All Samples have the same degree and distribution of polymerization...

The consistency (fluidity) of an initial mixture depends on the binder filler weight ratio, all other parameters (binder viscosity, microsphere type, shape, size, density, and mixing conditions) being equal. The mixtures are casting compositions (viscous fluids) at small microsphere concentrations, while they become molding compositions (pastes) at higher concentrations. Thus, the fluidity of a syntactic composition depends primarily on the filler concentration and not on the binder viscosity (Fig. 1)73 ... 

The -maxima and minima on viscosity-composition curves are reminiscent of those on vapour pressure-composition curves of binary, mixtures. 5 The vapour pressures and viscosities are equal at some temperatures, say T and To, and T and To respectively. Then To/T—To7T =C(T —T), where C is a constant. A plot of TojT—To IT against T—T gives a straight line in many cases, both for vapour pressure and viscosity in other cases, the vapour pressure shows a minimum and the viscosity a maximum, and the vapour pressure a maximum and the viscosity a minimum. Prasad, 6 from the relation with vapour pressure deduced the equation rj =rjjrio= +ac, where c=conc. of non-electrolyte. The theoretical value of a is 0 00652 the observed values were glucose 0 44, fructose 0 44, sucrose 0 78, independent of temperature. According to Errera, the curves depend on the electric dipolarity of the liquids if both are nonpolar, the curve is concave to the composition axis whilst if both are polar, it is convex. Wolkowa found that the viscosity of a solution is approximately proportional to its heat of dilution. There seems to be no relation between the viscosity and surface tension of a mixture of acetic acid and water (cf. salt solutions, 13.VIII E). Mixtures of isomorphous substances obey an approximately linear relation. 

Table 1. Initial component and composition dynamic viscosity (7) dependence on temperature.

Since the homologous polymer blends are known to be miscible It Is not surprising that mixtures of HDR with HDR or IDK with U>BE are miscible as well (12, 13). However, due to the diversity of polymerization methods and the variety of resulting molecular characteristics LLDra/LLDra systems are not always miscible (10, 14-15). In our laboratory three series of blends were prepared by Identical procedure of mixing the same LLDPE with two other LLDPE resins and with LDPE. The zero-shear viscosity vs. composition dependence, n vs. W2, of these systems Is presented In Fig. 1. Only the LLDPE s prepared with the same Tl-catalyst were found to be miscible (curve 2). Neither blend of LLDPE with LDPE (curve 3) nor LLDPE prepared with a vanadium catalyst LLDPE (curve 1) were miscible. There are Indications In the literature (8) that... 

Figure 1. Compositional dependence of the zero-shear viscosity for blends of a linear low density polyethylene (LLDPE) with (1) and (2) different LLDPE resins, and (3) with low density polyethylene, LDPE.

The results indicate that, for mold flux oxide compositions, the viscosity is dependent on the quantity of network forming oxides present, principally silica and alumina. This is demonstrated by the results of McCauley ( ) in Figure 1. In this case, it is the ratio of network forming ions to total anion concentration. However, as shown in Figure 2, the viscosity/reciprocal temperature relationship is not linear and cannot be adequately represented by the Arrhenius Equation over a wide temperature range. 

On the basis of the SANS results, a molecular mechanism has been recently proposed for the toughness enhancement of DN gels [34]. This mechanism rationalizes the changes in molecular structure of the DN gel constituents observed via in-situ neutron scattering measurements, the composition dependence of the solution viscosity, and the thermodynamic interaction parameters of PAMPS and PAAm molecules obtained previously from neutron scattering studies. More specifically, this proposed mechanism provides an explanation for the observed periodic compositional fluctuations in the micrometer range induced by large strain deformation. 

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