Cloud Point Of Solutions Research Articles

Effect of RESS dynamics on polymer morphology

In the rapid expansion of supercritical solutions (RESS), the time scale available for phase separation is shown to govern the morphology of precipitated polymers. When the solution cloud point curve (CPC) is crossed inside the RESS nozzle, precipitation occurs over microseconds, freezing the structures formed during early stages of phase separation. Polymers precipitated from chlorodifluoromethane under such conditions occur as 0.2-0.6-μm particles. When the CPC is crossed in the preheating zone upstream of the nozzle, precipitation occurs over tens of seconds. This allows the structures to grow, and polymers are precipitated experimentally as 1-13-μm particles and large aspect ratio fibers

Pressurized apparatus for measuring the cloud points of polymer solutions

A cloud point cell designed to operate at pressures up to 200 psig and temperatures up to 400 °F (204 °C), has been used extensively for evaluating aqueous polymer solutions. This cell, coupled with a visible spectrometer equipped with fiber optics connected to its light source and detector, can be used for determining cloud points of solutions. The polymer solution sealed in a glass ampoule and placed under a nitrogen pressure of 120 psig can be heated up to 400 °F (204 °C). The advantage of this setup over the standard turbidometers is extension of temperature to beyond the boiling point of the solvent.

Method for determination of cloud point of solutions of substances in water and oil media

Method for determination of cloud point of solutions of substances in water and oil media

Compatibility of polystyrene and poly(methyl methacrylate) in benzene. Effects of molecular weight and temperature

AbstractThe incompatibility of polystyrene and poly(methyl methacrylate) in benzene was examined at 20.1°, 40.0°, and 60.2°C. The incipient cloud points of solutions of equal weights of the two polymers were determined by a novel photometric method. Polystyrene samples with weight‐average molecular weights in the range of 3.27 × 105 to 6.43 × 104 and poly(methyl methacrylate) samples with weight‐average molecular weights in the range of 8.97 × 105 to 8.76 × 104 were used. Models describing the dependence on molecular weight of the critical concentration of a ternary polymer–polymer–solvent system, presented by Fuchs and by Kuhn et al., were examined in light of the experimental data. A modified model is proposed which gives an improved correlation of these results.

Semi-automatic apparatus for the study of temperature-dependent phase separations

The instrument described was designed to measure the temperatures at which phase separations occur, particularly the cloud points of solutions containing surfactants where high optical density makes visual estimations impracticable. The principle upon which the apparatus is based is that of the change in the ratio of the scattered to transmitted light when a liquid system ceases to be homogeneous. This is detected by means of a photoconductor bridge operating a simple servo mechanism.

The Correlation between Phase Inversion Temperature In Emulsion and Cloud Point in Solution of Nonionic Emulsifier

A model has been advanced in which it is proposed to regard the cloud point in solution of nonionic agent as akin to the phase inversion temperature in emulsion. In the latter, the mixing is macroscopic, whereas in the former the mixing is microscopic or on the bimolecular leaflet scale and the agent serves as an oil as well as an emulsifier. Phase inversion temperatures in hydrocarbon-water emulsions stabilized with polyoxyethylene alkyl phenyl ether have been determined for different hydrocarbons as a function of emulsifier concentration. It was found that the more soluble the hydrocarbon for a noionic emulsifier, the lower is the phase inversion temperature, above which O/W type emulsions invert to W/O type. A similar rule, that the more soluble the nonionic emulsifier for a definite hydrocarbon, the lower the phase inversion temperature, also holds. The effect of polyoxyethylene chain length and hydrocarbon chain length of the emulsifier on the phase inversion temperature have been studied. It was found that the cloud points in solutions of noionic emulsifiers saturated with various hydrocarbons and the phase inversion temperatures in emulsions were parallel, which supports the present model. The effect of temperature on the emulsion stability in connection with the phase inversion temperature is briefly discussed.

Factors affecting the solubility of nonionic emulsifiers

The effect of detergents, electrolytes, and organic liquids on the cloud point of Triton X-100, a nonionic emulsifier of the alkylphenol/polyethylene oxide type, is described. The lowering of the cloud point in dilute aqueous solution by electrolyte is a linear function of the ionic strength. The observed salting-out effect for the alkali metal and multivalent cations is roughly in the order of decreasing ion hydration. Crystalline nonelectrolytes cause only slight cloud point changes. Nonpolar liquids and anionic detergents significantly raise the cloud point of the nonionic emulsifier. As the polarity of the organic solubilizate is increased by introduction of double bonds and more polar constituent groups, the increase in cloud point is less marked. Aromatics and polar aliphatics even cause the cloud point to be sharply decreased. The cloud points of mixtures of nonionic emulsifiers lie intermediate between the cloud points of solutions of the pure components.

Factors affecting the solubility of nonionic emulsifiers

The effect of detergents, electrolytes, and organic liquids on the cloud point of Triton X-100, a nonionic emulsifier of the alkylphenol/polyethylene oxide type, is described. The lowering of the cloud point in dilute aqueous solution by electrolyte is a linear function of the ionic strength. The observed salting-out effect for the alkali metal and multivalent cations is roughly in the order of decreasing ion hydration. Crystalline nonelectrolytes cause only slight cloud point changes. Nonpolar liquids and anionic detergents significantly raise the cloud point of the nonionic emulsifier. As the polarity of the organic solubilizate is increased by introduction of double bonds and more polar constituent groups, the increase in cloud point is less marked. Aromatics and polar aliphatics even cause the cloud point to be sharply decreased. The cloud points of mixtures of nonionic emulsifiers lie intermediate between the cloud points of solutions of the pure components.