Dispersability characterization

Dispersions Characterization, Testing, and Measurement, Erik Kissa... 

The effect could be elucidated by ad tional axial dispersion characterization of GPC 1. An alternate approach is to utilize only THF in botii GPC 1 and 2 and to observe whether slices exit at the expected hydrodynamic volume. 

Axial dispersion characterization is a valuable by-product of coupling GPCs. By sampling chromatograms with the second GPC, extremely monodisperse fractions can be obtained and the concentration of misplaced molecules in any chromatogram slice revealed. 

Balke, S.T., Patel, R.D. (1980). Coupled GPC/HPLC copolymer composition and axial dispersion characterization. J. Polym. Sci., Polym. Lett. Ed. 18, 453 456. 

Axial Dispersion Characterization. Use of THF in both instruments as a method of examining the fractionation situation led to the investigation of CX as a method of supplying polymer of extremely narrow molecular weight distribution for resolution characterization of the second instrument (7). To do this, a ccmmercially available narrow molecular weight distribution steuidard was injected into the first instrument and sampled at its peak by the second instrument. 

Demokritou, P., Yang, C., Chen, Q. et al. (2002) An experimental method for contaminant dispersal characterization in large industrial buildings for indoor air quality (IAQ) applications. Building and Environment, 37 (3), 305-12. 

At first, we can note that the FeXp mean value is very close to F0 (250 Hz), and therefore compatible with the very low uncertainty about 250 Hz (accuracy of 6 10 iO), that is precisely obtained if we assume that the noise on the spectra is the only cause of dispersion. However, as it appears clearly on Fig. 3, this dispersion, characterized by the standard deviation of 2. 7 kHz, is too large in comparison with the noise s amplitude. The effective distribution of FeXp suggests a dependance versus time, probably related to fluctuating systematic shifts. 

When a fluid passes through a packed column, the flow is divided due to the packing. Modelling of these phenomena is carried out by superimposing a dispersion, characterized by a coefficient D on the convective plug flow of velocity U. This is the model for an axial dispersion reactor. This model allows characterisation of a flow with intermediate properties between those of the plug flow reactor and those of a continuous stirred reactor. 

Mild thixotropy has been observed in gelatiiized wheat starch dispersions characterized at low temperatures such as 25°C but not at 60°C and above (Doublier, 1981 Harrod, 1989 Bagley and Christianson, 1982). The time dependent rheological behavior shown by starch is attributed to structure formation by amylose leached into the suspending matrix on cooling to low gelling temperatures (Ellis et al., 1989). 

More recently, it was found that the hydroxylation state of the alumina has a determining influence upon the particle size of platinum crystallites. Controlled dehydroxylation of the alumina proved to be the most reliable method for preparing stable catalysts with gradual variations of the dispersion, and a continuous series of Pt/Al2O3 catalysts with dispersions (characterized by the H/Pt ratio) ranging from 0.04 to 1.0 was prepared by... 

The residual dispersion characterizes the errors of experiment provoked by the undetected factors, and the errors caused by the approximate character of the model. The relative value of these errors can be expressed by y = Oresl y... 

Dispersity. Foam cells usually have the shape of rounded polyhedra. Therefore, it is convenient to choose the radius a of the volume-equivalent bubble, that is, of a spherical bubble of the same volume as the cell as the single linear dimension characterizing the interior scale of foam. Foam consisting of cells of the same size is said to be monodisperse. This kind of foam is extremely rare. Usually, there exists a spectrum of radii ai,..., a in this case, the foam dispersity characterizes the mean linear dimension of the cell [214] ... 

Dominant axial dispersion (characterized by PCj St i) In chromatographic systems with relatively large effective mass transfer coefficients keff.i (be., low mass transfer resistance) the influence of axial dispersion, especially eddy diffusion, dominates the concentration profile. HETP and Nj are then independent of the interstitial velocity... 

In very recent years, tiller dispersion characterization has been brought again into light because of the difficulties encountered to disperse silica in rubber (Bomal etal., 1998,1993). 

Both the models of Figure 10.3 have the same general impedance spectrum as the one shown in Figure 10.5. Such a spectrum represents a dispersion, characterized by the following behavior At LF... 

Chitosan-magnesium aluminum silicate composite dispersions characterization of rheology, flocculate size and zeta petential. International Journal of Pharmaceutics. Vol.351, pp. 227-235. 

The zeta potential (Q is thought to be the same as the Stem potential which is defined at the plane dividing the Stem layer and the diffuse layer of the EDL. Zeta potential is an experimentally measurable electrical potential that characterizes the EDL, and it plays an important role in many apphcations such as stability of colloidal dispersion, characterization of biomedical polymers, electrokinetic transport of particles, and capillary electrophoresis, etc. In addition, zeta potentials of the particles and the channel wall are cmcial to the design and process control of microfluidic devices. A review on measuring the zeta potential of microfluidic substrates was provided by Kirby and Hasselbrink [3]. 

Kissa, E., Dispersions Characterization, Testing and Measurement, Surfactant Science Series, Marcel Dekker, New York, 1999, Vol. 84, chap. 13. 

The conversion is a function of Dal and the axial dispersion characterized by Bo as shown in Figure 3.20. With decreasing Bo the conversion diminishes at constant Dal (constant space time). At Dal = 5 a conversion of A = 0.99 is attained in a plug flow reactor Bo = oo), whereas the conversion drops to X = 0.83 for Bo = 0 (continuous stirred tank reactor). 

---