Viscosity-composition curves

The measurements presented here on emulsions of polyurethane and polyacrylonitrile dissolved in N-methylpyrrolidone can be explained well by theory. However, in the literature certain examples of comparable systems are given (e.g., polyacrylonitrile and cellulose-acetate dissolved in dimethylformamide (2)), which show a much more complicated behavior. These emulsions have even lower viscosities than that of the least viscous component. Thus, the viscosity-composition curves have minima. Such behavior cannot be explained by any of the models discussed above. It seems that the basic assumptions used in our analysis are not valid for such systems. 

Englishi thought the maxima on viscosity-composition curves could not be fully explained by compound formation. Some curves, for solutions of primary alcohols and fatty acids in benzene and carbon tetrachloride show... 

Usanovich considered that the viscosity-composition curve for a binary mixture was S-shaped when the components react to form a compound with a smaller viscosity than that of one component. 

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. 

Liquids with poor solvent action upon the resin make the best diluents. High-solvent power diluents produce sharp, that is, critical viscosity composition curves and may cause a rapid increase of paste viscosity during aging. 

In order to improve properties and compatibility of PP/EPDM blends, ternary blends and composites are sometimes prepared from the PP/EPDM blends. For instance, Sanchez et al. (10) prepared ternary blends of PP, high density polyethylene and EPDM with several blending ratios and investigated the melt rheological behaviors. They discussed the effect of the shear rate on the viscosity and flow curve in terms of the exponent of low power for a non-Newtonian liquid. They showed that addition of an elastomer to the polyolefin blends changes the shape of the viscosity-composition curve, and they discussed it in terms of the possible morphology of the blend. Similar works have been also reported by Ha et al. (11,12). 

Figures 5a and 5b show the trend of v and v vs for the three ED/W, ME/W, DME/W binary solvent systems. Although such a maxima observed for aqueous mixtures of different organic solvents has been attributed to the formation of an association complex [45], an appropriate explanation may be given as follows. The ascending part of viscosity-composition curves in the W-rich region (Figure 5a) represents structural promotion in the mixtures by gradual formation of supra-clusters of associated species (primeu y clusters). These supra-clusters aggregation may be provided in three different possible ways such as the association between i) the same species, ii) different species, and iii) the same and different species simultaneously. A progressive aggregation of these different types of primary clusters obviously would lead to an increase in the mixture viscosity and approach...

The shear viscosities of some of the investigated LCP/polymer blends, measured at a shear rate of 24 s are shown in Figure 1 as a function of the LCP content For all the blends, a considerable decrease of melt viscosity was observed as a result of the LCP addition. This is in agreement with literature data (i). A minimum is seen for some of the viscosity/composition curves (cf. NY/VB and PET/VA). This was shown to occur when the LCP s viscosity is higher than, or similar to, that of the matrix (5,4). 

The viscosities of many binary liquid systems display minima as functions of composition at constant temperature, so that negative values of D are also possible. Yajnik and his coworkers (265 ) long ago observed that very frequently an extremum in the isothermal vapor pressure-composition curve is accompanied by an extremum of the opposite sense in the viscosity-concentration curve. Data are apparently not available for solutions of very low-molecular-weight paraffins in carbon tetrachloride, but minima are found for the viscosities of solutions of CC14 with ethyl iodide, ethyl acetate and acetone, so that a minimum appears quite probable for mixtures of small aliphatic hydrocarbons with carbon tetrachloride. If this were true, the downward trend of the Meyer-Van der Wyk data on C17—C31 paraffins, earlier discussed in connection with the polyethylene plots of Fig. 14, would be understood. It will be recognized that such a trend is also precisely what is to be expected from the draining effect of the hydrodynamic theories of Debye and Bueche (79), Brinkman (45 ) and Kirkwood and Riseman (139). However, the absence of such a trend in the case of polyethylene... 

The different shape of the [ -composition curves for binary polymer mixtures (PMAA and PVP) in water and DMSO indicates the absence of the complexes in DMSO, The intrinsic viscosity passes through a minimum in water while in DMSO the viscosity is an additive function of the intrinsic viscosities of the individual components (Fig. 14). 

Slag Viscosity/Composition Correlations. Several attempts have been made in the past to define the linear portion of the viscosity/ temperature curve based on the composition of the coal ash. In the mid-1960 s, workers at the British Coal Utilization Research Association (BCURA) developed. two such correlations based on work with British (bituminous) coals, now generally referred to as the Watt-Fereday (4) and S (3) correlations (6). Unfortunately, attempts to apply this correlation to low-rank coal slags, using either ash or slag composition data, have been generally unsuccessful. 

The solution frequently becomes warm,12 and its refractive index,1 viscosity,2 freezing point-composition curve,3 and ultraviolet absorption spectrum 36 are not those which would be expected if no reaction took place. Usually hydrates or hemiacetals of simple aldehydes are too unstable to be isolated, but a number of them are actually known and their physical properties have been determined.4 When the carbonyl group is attached to an electron-attracting group (making the carbonyl carbon atom abnormally positive), stable hydrates are frequently formed. Glyoxal, chloral, and ketomalonic acid are common examples. 

The conplex viscosity as a function of composition curves would not be Inconsistent with the presence of one phase in the melt. 

In solvent formulas for ethylcellulose coating compositions, part of the toluene (up to 33 3%, but not as much as 662/3%) can be replaced by heptane without causing any appreciable increase in viscosity similar replacement of the alcohol by heptane causes a much greater viscosity increase (Curves 1, 4, and 5). 

Addition of alkali oxides to germania initially reduces the thermal expansion coefficient, which passes through a minimum at 2 to 5 mol% alkali oxide. Further additions of alkali oxides result in a continuous increase in the thermal expansion coefficient out to the limit of glass formation. The position of the minimum in thermal expansion coefficient is near the low alkali germanate anomaly in viscosity and glass transformation temperature, which occurs at 2 mol% alkali oxide. No unusual behavior in the thermal expansion coefficient is found in the 15 to 20 mol% alkali oxide region where the traditional germanate anomaly in density and refractive index occurs. Replacement of alkali oxides by alumina reduces the thermal expansion coefficient, but has little effect on the shape of the thermal expansion coefficient versus composition curve, which still displays a minimum at 2 to 5 mol% alkali oxide. 

Fig. 4. Relation between ideal and real viscosities (upper curve and markers) and diffusivities (lowercurve eind markers) and composition in an ethanol (i) +water (2) system [1-3] [4] using Van Laar model... 

Properly spoken these line arc projections of tie lines occurring in the tetrahedral isotherm Water G+4 iV. The fourth component, water, has however been left out of consideration in the triangles of figs. 32 and 33, which represent only the colloid compositions of the mixtures. 2 e.g. shape of the viscosity-pH curve. See p. 208, Fig. 20,... 

The intrinsic viscosities were determined by dilution at constant polymer-NaDS complex composition. The hydrodynamic volume of the polymer is increasing with the NaDS-content of the complex. In 0.1 M NaN03 solution a minimum appears in the intrinsic viscosity vs. complex composition curves for the poly-(vinyl-pirrolidone)-NaDS and poly-(vinyl-alcohol vinyl-acetate) copolymer-NaDS system. 

Composition expected from viscosity endblocker curve "a" is approximately 70,... 

As shown in the figure, the viscosity/temperature curves for the arsenic selenic glass family shift nearly uniformly to higher temperatures as the molar fraction of arsenic is increased in steps from 10% to 40% in the system, meaning that the higher-selenium-content glasses can be processed via thermal routes at very low temperatures however, the viscosity changes very rapidly with temperatures in these selenium-rich compositions, which makes some fiber fabrication routes very difficult to control accurately. 

The increase in fuel viscosity with temperature decrease is shown for several fuels in Figure 9. The departure from linearity as temperatures approach the pour point illustrates the non-Newtonian behavior created by wax matrices. The freezing point appears before the curves depart from linearity. It is apparent that the low temperature properties of fuel are closely related to its distillation range as well as to hydrocarbon composition. Wide-cut fuels have lower viscosities and freezing points than kerosenes, whereas heavier fuels used in ground turbines exhibit much higher viscosities and freezing points. 

---