Viscosity, K-value

The viscosity of aqueous solutions of povidone depends on their average molecular weight. This can therefore be calculated from the viscosity, giving the viscosity-average molecular weight (see Section 2.2.6). Fig. 7 shows the very considerable differences in viscosity between solutions of the different povidones in water, as a function of their concentration. A 20% aqueous solution of povidone K 12 shows hardly any visible difference to pure water, while a 20% solution of povidone K 90 in water gives high viscosities until 5000 mPa-s. 

Nominal K-value Concentration Relative viscosity USP and Ph.Eur. limits 

If the concentrations of the solutions are increased, the viscosity ranges become even greater, as can be seen from the values given in Table 8 for io% (g/ml) solutions in water. These typical values have been taken from the former monograph Losliches Polyvidon in Deutscher Arzneimittel-Codex 1986. 

The viscosity, e. g. of povidone K 30 in water at concentrations up to 10%, is hardly affected by temperature (Fig. 8). At higher concentrations, however, the viscosity decreases rapidly with increasing temperature. 

It was reported that most cations increase the viscosity and most of anions decrease the viscosity of povidone K 90 solutions [530]. Some polymers such as carragheenan show a synergistic viscosity increasing effect with the high-molecular povidone K 90. 

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RValue Relative viscosity K Value Relative viscosity... 

K) were investigated. From an equation of state for iron the densities at these temperatures could be predicted to enable the simulations to be performed. A periodic system containing 64 atoms was used and the simulation run for 2 ps after equilibration. The calculated pressure agreed within 10% with the experimental values (330 GPa at the inner core boundary and 135GPa at the core-mantle boundary). Additional parameters could also be calculated, including the viscosity, the values for which were at the low end of previous suggestions. 

Grade viscosity, mPa-s (=cP) Fikentsher K value Kraemer and Samow Ring-and-b all Mol weight... 

Inherent viscosity, ASTM D1234 Relative viscosity, ASTM D1234 K value, (DIN 53726) Af X 10-" Af X 10-"... 

The identity tensor by is zero for i J and unity for i =J. The coefficient X is a material property related to the bulk viscosity, K = X + 2 l/3. There is considerable uncertainty about the value of K. Traditionally, Stokes hypothesis, K = 0, has been invoked, but the vahdity of this hypothesis is doubtful (Slattery, ibid.). For incompressible flow, the value of bulk viscosity is immaterial as Eq. (6-23) reduces to... 

Average molecular weight ISOIR174- 1961(E) viscosity number K-value ASTM DI243-58T ... 

The design procedure described above will, in theory, be applicable only to samples that are separated by isocratic development. Under gradient elution conditions the (k ) value of each solute is continually changing, together with the viscosity of the... 

The correlation factor, k, is a function of the liquid drop size, liquid viscosity, liquid load, disengaging space, type of mesh weave, etc. k varies somew hat with system pressure as pressure increases the k value decreases. The manufacturers should be consulted for final design k valves for a sys-... 

Clearly, shear thinning behaviour corresponds to nshear thickening behaviour to n> 1. The special case, n = 1, is that of Newtonian behaviour and in this case the consistency coefficient K is identical to the viscosity fx. Values of n for shear thinning fluids often extend to 0.5 but less commonly can be as low as 0.3 or even 0.2, while values of n for shear thickening behaviour usually extend to 1.2 or 1.3. 

Their molecular weight or degree of polymerization, often expressed as K value or K-wert, inferred from viscosity measurements. Figure 4.33 (a b) displays some examples of polymerization degrees and molecular weights versus K values. Slightly different data can be found quoted elsewhere because several methods to measure K values exist. 

Whilst not all workers agree as to the relevance of individual k values, all agree that for two polymers with similar Mn values, then the polymer with the lowest limiting viscosity value will be the more branched. Price [65, 66] has observed a similar trend in molar mass with irradiation, albeit in a sonochemically polymerising system. 

As pointed out in Section I, viscosities are really meaningful if compared only for Newtonian fluids or at specified shear rates for other materials. A similar limitation must be imposed on the consistency indexes K and K values of either are comparable only for fluids with the same flow behavior indexes n or n . 

Use these data to evaluate the intrinsic viscosity for the polymer and use the a and k values from Problem 9 to calculate the molecular weight from the value of [r/]. 

Water droplets settle out of a lighter liquid hydrocarbon phase because of gravity. The water is denser than the liquid hydrocarbons. Liquid droplets settle out of a lighter gas phase because of gravity. What is the difference The difference is viscosity. We neglected the effect on the gas viscosity when calculating the K value in KO drums. Gas viscosities are almost always very low. 

The ratio of elastic constants Ku, calculated for the S-effect according to the equation (4) appeared to be (Kn (polymer XIV)/Kn (polymer XIII)) x 1 100 and (Ku (polymer XVI)/Kn (polymer XV)) x 1 36. Yet, as we have just indicated, taking into account molecular masses of the LC polymers and reducing k, values for various polymers to equal values of DP one may come to substantially different values for ratios of constants presented. It is necessary to note that up to date no quantitative data on the determination of elastic constants of LC polymers has been published (excluding the preliminary results on Leslie viscosity coefficients for LC comb-like polymer127)). Thus, one of the important tasks today is the investigation of elastic and visco-elastic properties of LC polymers and their quantitative description. 

A k value of 0.1910 was found and is in perfect accordance with an extensive study made by Wirick et al. (51) on 26 different HEC samples with intrinsic viscosities ranging from 1700 mL/g to 170 mL/g and with MS values between 1.6 and 2.7. 

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