Tomlinson Fort

Ultralow interfacial tensions and their relation to phase separation in micellar solutions

Interfaces having very low tensions can be produced when a micellar solution separates into a micelle-rich and a micelle-lean phase. For separation to occur under reasonable conditions, the micelles must contain enough solubilized oil or water to be about 100 A in diameter or larger. A simple model is developed to predict the conditions for phase separation and the compositions of the phases in equilibrium. Interfacial tension is calculated by adapting Cahn and Hilliards approach (J. Chem. Phys. 28 , 258 (1958)). Results show that interfacial tensions can be 10 −2 dyn/cm or lower even when the system is far from a consolute point. Predictions of the theory are in general agreement with the data of Healy et al . (Soc. Petrol. Eng. J. 16 , 147 (1976)) on low interfacial tensions in oil-water systems with a synthetic petroleum sulfonate surfactant.

Pendant Drop Technique for Measuring Liquid Boundary Tensions

Boundary tension tends to make a liquid drop hanging (pendant) from the tip of a capillary tube take the form of a sphere. In a gravitational field, the sphere is distorted into an elongated “tear drop” shape. This distortion increases with effective drop density and decreases as liquid boundary tension becomes greater. Consequently, it is possible to calculate boundary tension if gravity and liquid densities are known and drop shape can be accurately measured. These measurements and calculations are the subject of this report.

Polymerization of oriented monolayers of vinyl stearate

Abstract Oriented monolayers of vinyl stearate were photolytically polymerized with uv radiation at the air-water and nitrogen-water interfaces. Experiments were conducted on a film balance. Measurements of surface pressure, surface potential, relative surface viscosity, and infrared internal reflectance spectra provided means for characterizing reactants and products, and determining reaction kinetics. Complete conversion of monomer was achieved. The monolayer polymerization was found to be best fit by a second-order rate expression. The reaction rate constant increased as the irradiation area was increased.

Phase behavior of pH-dependent microemulsions

Abstract A model microemulsion system which exhibits pH-dependent phase behavior has been developed using oleic acid as the surfactant. Ultralow interfacial tensions were observed using an automated sessile drop technique. The effect of salinity on phase behavior can be counterbalanced by pH adjustment under appropriate conditions. Added electrolyte makes the surfactant system hydrophobic while an increase in pH can make it hydrophilic by ionizing more surfactant. Calculations based on the Gouy-Chapman theory are presented to describe the effects of pH and salinity. The study is relevant to enhanced oil recovery by chemical flooding.

SPONTANEOUS EMULSIFICATION IN OIL-WATF.R.-SURFACTANT SYSTEMS*

ABSTRACT Mixtures of several alkl-aryl sulfonates with brine were carefully contacted with oil. The mixtures contained a few percent surfactant and were either liquid crystalline phases or dispersions of liquid crystalline particles in brine. At high salinities a brine layer developed between the initial phases and an emulsion of brine drops in oil formed spontaneously at discrete sites along the surface of contact. At low salinities no emulsifixation was seen. The occurrence of emulsification only at high salinities is explained in terms of local supersaturation produced by the diffusion process.

Phase behavior of dilute sodium dodecyl sulfate-hexanol-brine systems

ABSTRACT Dilute aqueous “solutions” of anionic surfactants injected during enhanced oil recovery processes usually contain liquid crystalline material. Phase behavior has been studied in a model system containing sodium chloride brine with surfactant, alcohol, and salt contents maintained below 6, 10, and 3 weight percent respectively. Pseudoternary phase diagrams at constant salinities are used to represent the results. Some interpretation of the results is given in terms of micellar shape transformations produced by changes in the relative hydrophilic and hydrophobic properties of surfactant-alcohol mixtures.

The Effects of High Contact Pressures and Temperatures on the Adhesion of Amorphous Polystyrene to Borosilicate (Pyrex) Glass

Abstract The effects on adhesive joint strength of four pressure-temperature histories, each over the range of pressures from 1 to 1500 bars and temperatures from 25 to 200°C, has been investigated with polystyrene-Pyrex glass butt joint specimens. The various pressure-temperature histories were designed to show the separate effects of permanent stresses, transient stresses and interfacial contact on joint strength. This strength increased as the number of stress concentration loci were reduced through application of high contact pressures on the melt. However, isobaric solidification of the polymer led to a maximum in fracture stress as a function of applied molding pressure because of the existence of a critical pressure at which permanent thermal stresses were minimized. A series of isothermal compression-decompression molding operations showed fracture stress to increase with interfacial contact area until maximum contact was achieved. A 100 per cent gain in bond strength was realized when interfacial...