Surface tension

About: Surface tension is a research topic. Over the lifetime, 25410 publications have been published within this topic receiving 695471 citations.

The interface in binary mixtures of polymers containing a corresponding block copolymer: Effects of industrial mixing processes and of coalescence

Abstract: In theories of the minor phase (domain) formation in polyblends rendered as emulsions it is usually assumed that the size and shape of the domains are the result of melt viscosity effects (Taylor, Wu) or viscoelasticity effects (VanOene, Elmendorp) being balanced by interfacial tension. This assumption would predict a monotonic decrease of the domain size to a final limiting size with increasing energy of mixing. However, a systematic study of the dependence of domain morphology on industrial mixing processes which was carried out on a “model” LDPE/PS (2/1) mixture and the related polyalloy (i.e., the same mixture with a corresponding block copolymer as compatibilizer) does not support this expectation. Doirain size was found to go through a minimum as mixing energy was increased. A similar minimum was seen in data on specific volume of the melt vs. mixing energy, which indicates a correlation between melt specific volume and domain size. Calculation of the approximate surface area of the domains using a simple model of domain shape indicated that total interfacial energy in the polyblend and/or polyalloy is a trivial part of the mixing energy introduced. These calculations also indicated that if compatibilizer was located entirely at the interface, the surface layer would have a thickness of about 90 nm. Some micrographs seem to show such a surface layer. We propose that an abrasion mechanism is responsible for the early stage of the dispersion process, and that the final domain size may be controlled by a dispersion-coalescence equilibrium. This is compared with the theories of final particle size proposed by VanOene and Wu.

Methane and Carbon Dioxide Hydrate Phase Behavior in Small Porous Silica Gels: Three-Phase Equilibrium Determination and Thermodynamic Modeling

Abstract: Hydrate phase equilibria for the binary CH4 + water and CO2 + water mixtures in silica gel pores of nominal diameters 6.0, 15.0, and 30.0 nm were measured and compared with the calculated results based on van der Waals and Platteeuw model. At a specified temperature, three phase H−LW−V equilibrium curves of pore hydrates were shifted to the higher pressure region depending on pore sizes when compared with those of bulk hydrates. The activities of water in porous silica gels were expressed with a correction term to account for both capillary effect and activity decrease. By using the values of interfacial tension between hydrate and liquid water phases which were recently presented by Uchida et al.,5 the calculation values were in better agreement with the experimental ones. The structure and hydration number of CH4 hydrate in silica gel pores (6.0, 15.0, and 30.0 nm) were found to be identical with those of bulk CH4 hydrate through NMR spectroscopy.

Structure and Collapse of Particle Monolayers under Lateral Pressure at the Octane/Aqueous Surfactant Solution Interface†

Abstract: We report a study of the compression of monolayers of monodisperse spherical polystyrene particles at the interface between aqueous surfactant solutions and octane. The particle size (2.6 μm diameter) was selected so that direct in situ microscopic observation of the monolayer structure could be made during lateral compression and “collapse”. Monolayers have been formed on a miniature Langmuir trough placed on a microscope stage. Our study has focused on (a) the relationship between the monolayer collapse pressure, Πcol, and the interfacial tension, γ*, of the oil/water interface in the absence of a particle monolayer and (b) the mode of monolayer “collapse” at high surface pressure. Interfacial tensions γ* have been adjusted (in the range 50−4 mN m-1) by addition of surfactants over a range of concentration. We find that the monolayer collapses by buckling (folding) when the surface pressure is equal to the surface tension of the oil/water interface. Particle promotion out of the interface is not observe...

Effect of volume concentration and temperature on viscosity and surface tension of graphene–water nanofluid for heat transfer applications

Abstract: In the present study, the effect of volume concentration (0.05, 0.1 and 0.15 %) and temperature (10–90 °C) on viscosity and surface tension of graphene–water nanofluid has been experimentally measured. The sodium dodecyl benzene sulfonate is used as the surfactant for stable suspension of graphene. The results showed that the viscosity of graphene–water nanofluid increases with an increase in the volume concentration of nanoparticles and decreases with an increase in temperature. An average enhancement of 47.12 % in viscosity has been noted for 0.15 % volume concentration of graphene at 50 °C. The enhancement of the viscosity of the nanofluid at higher volume concentration is due to the higher shear rate. In contrast, the surface tension of the graphene–water nanofluid decreases with an increase in both volume concentration and temperature. A decrement of 18.7 % in surface tension has been noted for the same volume concentration and temperature. The surface tension reduction in nanofluid at higher volume concentrations is due to the adsorption of nanoparticles at the liquid–gas interface because of hydrophobic nature of graphene; and at higher temperatures, is due to the weakening of molecular attractions between fluid molecules and nanoparticles. The viscosity and surface tension showed stronger dependency on volume concentration than temperature. Based on the calculated effectiveness of graphene–water nanofluids, it is suggested that the graphene–water nanofluid is preferable as the better coolant for the real-time heat transfer applications.