Estimating cloud point from

In order to estimate the cloud point from viscoelastic oscillatory measurements, we propose to extrapolate the critical temperature to -> 0,... 

In this study we examined the influence of concentration conditions, acidity of solutions, and electrolytes inclusions on the liophilic properties of the surfactant-rich phases of polyethoxylated alkylphenols OP-7 and OP-10 at the cloud point temperature. The liophilic properties of micellar phases formed under different conditions were determined by the estimation of effective hydration values and solvatation free energy of methylene and carboxyl groups at cloud-point extraction of aliphatic acids. It was demonstrated that micellar phases formed from the low concentrated aqueous solutions of the surfactant have more hydrophobic properties than the phases resulting from highly concentrated solutions. The influence of media acidity on the liophilic properties of the surfactant phases was also exposed. 

Thus, an estimation can be made of the hydrophilicity of the crown ring. The acetal-type crown ring obtained from hexaethyl-ene glycol and a higher aliphatic aldehyde is estimated to be e-quivalent to about four OE units in an alkyl POE monoether, from our study of the cloud point (11). Moroi et al. concluded, from a comparison of the cmc, that a diaza-18-crown-6 is equivalent to 20 OE units in the usual type of nonionic (12). Okahara s group evaluated the effective HLB based on the cloud point, phenol index and phase-inversion-temperature in emulsion of oil/water system and they concluded that 18-crown-6 and monoaza-18-crown-6 rings with dodecyl group are approximately equivalent to 4.0 and 4.5 units, respectively, of OE chains with the same alkyl chain (17). 

Three different isothermal crystallization experiments were performed in this work classical static (i.e., quiescent) crystallization in the DSC apparatus, dynamic crystallization with the apparatus described above, and dynamic-static crystallization. Dynamic isothermal crystallization consisted in completely solidifying cocoa butter under a shear in the Couette apparatus. Comparison of shear effect with results from literature was done using the average shear rate y. This experiment did not allow direct measurement of the solid content in the sample. However, characteristic times of crystallization were estimated. The corresponded visually to the cloud point and to an increase of the cocoa butter temperature 1 t) due to latent heat release. The finish time, was evaluated from the temperature evolution in cocoa butter. At tp the temperature Tit) suddenly increases sharply because of the apparition of a coherent crystalline structure in cocoa butter. This induces a loss of contact with the outer wall and a sharp decrease in the heat extraction. 

Table 5.10 Study of the Effects of 4 Factors on Cloud Point and Turbidity of a Liquid Formulation Experimental Domain and Coefficient Estimations from 2 Design [from reference (2), with permission]...

BAK Bakshi, M.S., Kaur, N., Mahajan, R.K., Singh, J., and Sing, N., Estimation of degree of counterion binding and related parameters of monomeric and dimeric cationic surfactants from cloud point measurements by using triblock polymer as probe. Coll. Polym. Sci., 284, 879, 2006. 

In this case, with the P-phase semipermeable to mass transfer, the thermodynamic simulation was carried out as follows. Once a and P-phases were generated, kinetic equations were solved independently for both phases. After a differential time, the a-phase was driven to equilibrium segregating a differential amount of material rich in modifier that was incorporated in the P-phase. At this time, the P-phase, modified both by the material received from the a-phase and the evolution of species through the continuation of the polymerization, was driven to equilibrium. Under these conditions, a secondary phase separation (i.e. a phase separation inside the P-phase) took place, as shown in Fig. 24. The Y-phase (dispersed phase inside particles of the p-phase) is rich in epoxy-amine copolymer whereas the 5-phase (continuous matrix inside particles of the P-phase - also called submatrix), is rich in the modifier. While y- and 5-phases are always at equilibrium, a- and P-phases are not, due to the semipermeable character of the latter. It is observed that, as most of the phase separation takes place at conversions close to the cloud point, the P-phase keeps a significant proportion of epoxy-amine copolymer even at high overall conversions. This agrees with experimental estimations of the composition of dispersed-phase particles in rubber-modified epoxies [103,104]. 

We illustrate the theory with blends of copoly (styrene acrylonitrile) + poIy(me-thyl methacrylate) and those of co poly (styrene acrylonitrile) + copoly(butadiene acrylonitrile), for which experimental data are available from literature [76,77]. The quantities s, ..., Sj may be estimated from van der Waals surfaces used in the UNIFAC-tables [78] or from an empirical fit to the available experimental data. The G parameters, a, b, c, d, have to be adjusted to fit experimental cloud-points or critical point and/or spinodal curve. The gy parameters in Eq. (155) may be obtained from thermodynamic data sensitive to them or from the cloud-point curve of subsystems, if available. 

Figure 1 depicts the experimental cloud points and the nematic-isotropic transition temperatures in comparison with the theoretical phase diagram of the PMMA-OH/E7 PDLC system. The phase diagram calculation was carried out based on the combined Flory-Huggins (FH) and Maier-Saupe (MS) free energies using r = 2.25 and a = -4.0. The b value was estimated from the critic temperature using x = a + (Xc-a)Tc /T. 

Hsiao et al. reported a cloud point pressure at approximately 150-170 bar and 40 C for 4 wt% of a PFOA sample (Af = 1,000,000 g/mol) [30], An LCST-type behavior was also noted as a result of the positive dependency of pressure upon increasing temperatures. Through neutron scattering experiments, this high solubility of PFOA could be related to a positive second virial coefficient (A2) in conditions as mild as 207 bar and 45°C in the case of sample with an equal to 36,500 g/mol [31]. However, the theta pressure was not determined. In another set of experiments, the positive A2 was found to be a decreasing function of molecular weight, as expected from the case of polymer solutions in incompressible solvents [32]. A2 was also estimated to be proportional to at the power of -0.4. 

Davies [93] has shown that the agreement between HLB numbers calculated from the above equation and those determined experimentally is quite satisfactory. Various other procedures were developed to obtain a rough estimate of the HLB number. Griffin found good correlation between the cloud point of 5 % solution of various ethoxylated surfactants and their HLB number. 

Figures 12.1.22 and 12.1.23 explain technical principles behind formation of efficient and selective membrane. Figure 12.1.22 shows a micrograph of hollow PEI fiber produced from N-methyl-2-pyrrolidone, NMP, which has thin surface layer and uniform pores and Figure 12.1.23 shows the same fiber obtained from a solution in dimethylformamide, DMF, which has a thick surface layer and less uniform pores. The effect depends on the interaction of polar and non-polar components. The compatibility of components was estimated based on their Hansen s solubility parameter difference. The compatibility increases as the solubility parameter difference decreases. Adjusting temperature is another method of control because the Hansen s solubility parameter decreases as the temperature increases. A procedure was developed to determine precipitation values by titration with non-solvent to a cloud point. Use of this procedure aids in selecting a suitable non-solvent for a given polymer/solvent system. Figure 12.1.24 shows the results from this method. Successfid in membrane production by either non-solvent inversion or thermally-induced phase separation requires careful analysis of the compatibilities between polymer and solvent, polymer and non-solvent, and solvent and non-solvent. Also the processing regime, which includes temperature control, removal of volatile components, uniformity of solvent replacement must be carefully controlled.

In the cloud tesi (D97) the oil is cooled, from at least 25°F above the cloud point, in a specified test jar. The cooling bath is held between 15 and 30°F below the cloud point of the oil. At intervals the test jar is removed from the brine bath without disturbance to the oil, and the temperature at- which distinct cloudiness or haziness appears in the bottom of the jhr is recorded as the cloud point. The cloud point of dark-colored oils may be estimated by the temperature at which the viscosity increases rapidly. The pour test (D97) is conducted in much the same manner. However, the oil is first heated to 115°F, to be sure that all wax has dissolved, and cooled to 90 F before the test. As in the cloud test, the bath is held 15 to 30°F below the estimated pour point. 

In spite of the deviation from the mean-field type behavior, the coexistence curve of the blend B was well described by the Flory-Huggins theory under the quasibinary approximation with the interaction parameter x that was consistent with those estimated by the molecular weight dependence of cloud points. 

Numerous analyses of data routinely collected in the United States have been performed by the U.S. National Climatic Center, results of these analyses are available at reasonable cost. The joint frequency of Pasquill stability class, wind direction class (primarily to 16 compass points), and wind speed class (in six classes) has been determined for various periods of record for over 200 observation stations in the United States from either hourly or 3-hourly data. A computer program called STAR (STability ARray) estimates the Pasquill class from the elevation of the sun (approximated from the hour and time of year), wind speed, cloud cover, and ceiling height. STAR output for seasons and the entire period of record can be obtained from the Center. Table 21-2 is similar in format to the standard output. This table gives the frequencies for D stability, based on a total of 100 for all stabilities. 

---