Showing papers on "Surface tension published in 1969"
TL;DR: In this article, a method for measuring the surface energy of solids and for resolving surface energy into contributions from dispersion and dipole-hydrogen bonding forces has been developed based on the measurement of contact angles with water and methylene iodide.
Abstract: A method for measuring the surface energy of solids and for resolving the surface energy into contributions from dispersion and dipole-hydrogen bonding forces has been developed. It is based on the measurement of contact angles with water and methylene iodide. Good agreement has been obtained with the more laborious γc method. Evidence for a finite value of liquid-solid interfacial tension at zero contact angle is presented. The method is especially applicable to the surface characterization of polymers.
7,695 citations
TL;DR: In this paper, the authors considered a variety of problems in hydrodynamics and in the theory of convective heat and mass transfer in two-phase systems with mobile interphase boundary (liquid-liquid or liquid-gas).
Abstract: Inlroduction.--In considering a variety of problems in hydrodynamics and in the theory of convective heat and mass transfer in two-phase systems with mobile interphase boundary (liquid-liquid or liquid-gas) one encounters so-called capillary phenomena, i.e., phenomena caused by the existence of surface tension on the interphase boundary. These phenomena include, for example, the retardation of droplets and bubbles moving in a liquid that contains dissolved surface-active substances, formation of surface waves in liquids under the influence of different kinds of disturbances, the motion of liquids in thin capillaries, etc. Capillary phenomena may occur in two cases: (a) when the surface of phase separation possesses considerable curvature, and (b) when the surface tension varies from point to point on the surface. In both cases, there arise forces near the interphase boundary that change the nature of the motion in each of the phases or induce motion originally absent. Formally, the effect of surface tension on the hydrodynamics (and via the hydrodynamics also on the heat and mass transfer) appears in change of the boundary conditions on the interface. According to the basic principles of hydromechanics (1), the condition of a balance of the forces acting in each phase must be fulfilled on the mobile phase boundary. This condition may be written in the following general form:
401 citations
01 Jan 1969
TL;DR: It is a common observation that oil, when spilled on water, tends to spread outward on the water surface in the form of a thin continuous layer as mentioned in this paper, which is the result of two physical forces: the force of gravity which causes the lighter oil to seek a constant level by spreading horizontally, just as it would on a plane horizontal solid surface and the surface tension force of pure water, which is usually greater than that of the oil film floating on water.
Abstract: It is a common observation that oil, when spilled on water, tends to spread outward on the water surface in the form of a thin continuous layer. In those instances where this layer is as thin as a wave length of visible light, an iridescent color of the film, caused by light interference, is observed. This tendency to spread is the result of two physical forces: the force of gravity which causes the lighter oil to seek a constant level by spreading horizontally, just as it would on a plane horizontal solid surface, and the surface tension force of pure water, which is usually greater than that of the oil film floating on water. While the oil layer could spread while still remaining intact until it had formed a monomolecular layer, spreading usually stops when the layer is much thicker than this, most likely because of a change in the surface tension properties of the oil.
376 citations
TL;DR: The theory of van der Waals and of Cahn and Hilliard is generalized by replacing the equation of state assumed originally by one that reproduces more accurately the known thermodynamic singularities at the critical point as mentioned in this paper.
Abstract: The theory of van der Waals and of Cahn and Hilliard, which yields the density or concentration profile through an interface and the associated interfacial tension, is generalized by replacing the equation of state assumed originally by one that reproduces more accurately the known thermodynamic singularities at the critical point. Though the correct equation of state is not known, its presumed homogeneity of form is alone sufficient to allow most features of the interface to be determined explicitly. In particular, the maximum density gradient in the interface, the asymptotic behavior of the interface profile at large distances from the position of its maximum gradient, and the surface tension, are each obtained up to a dimensionless, and presumably universal, proportionality constant that reflects only the functional form of the equation of state. Numerical evaluation of the surface tension requires a knowledge of the limits approached by the correlation length and compressibility in the homogeneous flu...
328 citations
TL;DR: In this paper, an exact solution for the equations for free convection in a planar horizontal layer of liquid with a constant temperature gradient at the boundaries is found for two cases of boundary conditions for the velocity: 1) the liquid is bounded by two solid planes, 2) the upper surface of the liquid was free, and the surface tension is a function of temperature.
Abstract: An exact solution is found for the equations for free convection in a planar horizontal layer of liquid with a constant temperature gradient at the boundaries. Two cases of boundary conditions for the velocity are considered: 1) the liquid is bounded by two solid planes, 2) the upper surface of the liquid is free, and the surface tension is a function of temperature.
194 citations
190 citations
01 Jul 1969
TL;DR: The surface tension of water has been measured at small temperature intervals as discussed by the authors, and analysis of these data and of data from the literature suggests the absence of significant inflection in the variation of the surface tension with temperature.
Abstract: The surface tension of water has been measured at small temperature intervals. Analysis of these data and of data from the literature suggests the absence of significant inflections in the variation of the surface tension of pure water with temperature.
161 citations
TL;DR: In this article, a thermodynamic fundamental equation for the surface phase of a solid exposed to an adsorbing gas is derived, which is more general than the corresponding equation given by Gibbs in the sense that it is applicable with less restriction as to the state of strain of the solid surface.
142 citations
TL;DR: In this article, a technique for including the effects of surface tension in time-dependent, hydrodynamics calculations is described, where the fluid interface is initially marked with a sequence of interface particles, which thereafter move through the computation mesh at the local fluid velocity.
133 citations
TL;DR: Bubble growth in constant and time-dependent pressure fields has been formulated taking into account not only the effects of surface tension, inertia of liquid, heat conduction in the liquid, but also the effects that nonequilibrium at the liquid-vapor interface, and the varying density of the vapor bubble as discussed by the authors.
132 citations
TL;DR: In this paper, a non-linear regression calculation procedure was developed which permits calculation of surface tension and contact angle for any sessile drop shape with a contact angle greater than zero.
TL;DR: In this article, the surface tension of poly(isobutylenes) in the molecular weight range 400-3000 was determined at 24°C and a simple free-volume argument seems to be consistent with this empirical observation.
TL;DR: In this article, the authors measured the contact angles of water, glycerol, formamide, ethylene glycol, 1-bromonaphthalene, and bromobenzene on surfaces of polyethylene, polystyrene, polyacetal, polycarbonate, poly(ethylene terephthalate), and poly(tetrafluoroethylene-co-hexafluoropropylene).
TL;DR: In this paper, a new technique for including the effect of surface tension in time-dependent, incompressible flow calculations is used to examine the linear and nonlinear phases of Rayleigh-Taylor instability.
Abstract: A new technique for including the effect of surface tension in time‐dependent, incompressible flow calculations is used to examine the linear and nonlinear phases of Rayleigh‐Taylor instability. The variation of the linear growth rate with the surface tension coefficient and (for a fixed coefficient) with the wavenumber of the perturbation is shown to be in good agreement with Chandrasekhar's analytic prediction. In the nonlinear regime, it is shown how surface tension affects the growth of the Rayleigh‐Taylor spike and provides the mechanism for drop separation from the spike.
TL;DR: In this paper, a sufficient condition for stability was developed for the motions in a horizontal, heated layer subject to buoyancy and surface tension effects, where the free surface is assumed to be non-deformable (Pearson's 1958 model).
Abstract: The energy theory, giving a sufficient condition for stability, is developed for the motions in a horizontal, heated layer subject to buoyancy and surface tension effects. The free surface is assumed to be non-deformable (Pearson's 1958 model).It is shown that the equations governing the energy theory are the symmetric part of the time-independent linear theory problem, and that the surface tension terms behave like a bounded perturbation to the Benard problem. The qualitative behaviour of the optimal stability boundary as a function of its parameters is given. The optimal stability boundary is computed, and compared with previous linear and non-linear stability theories in terms of allowable subcritical instabilities.
TL;DR: In this paper, an axisymmetric gas jet of air impinging on both water and wet cement was performed and analyzed and detailed measurements of the solidified cavity shape were made and shown to agree well with theory.
Abstract: Experimental tests of an axisymmetric jet of air impinging on both water and wet cement were performed and analyzed. Since the cavities formed on the water were unsteady and irregular, cavities were formed on wet fast-setting cement and allowed to set with the jet impinging. In this way, detailed measurements of the solidified cavity shape were made and shown to agree well with theory. This correlation of the data with the theory indicates that little gas was entrained in the liquid and that the influence of liquid viscosity and surface tension was small for the experimental conditions tested. A simplified analysis is also presented for an incompressible axisymmetric gas jet impinging normally on a liquid surface. The analysis was effected by combining the following physical conditions and assumptions: (i) the stagnation pressure corresponding to the centreline conditions of the jet at the bottom of the cavity is equal to the hydrostatic pressure, wherein an empirical turbulent jet decay law is used to predict the variation of stagnation pressure with distance from the nozzle; (ii) the force on the liquid is equal to the total change in normal momentum, which is equal to the weight of the displaced liquid; (iii) the shape of the cavity is a paraboloid.
TL;DR: In this article, the authors measured the interfacial tension along the boundary formed between two immiscible polymer liquids by the pendant drop method and calculated the separate contributions to the surface tension by dispersion and dipole interaction forces, in accordance with the procedure proposed by Fowkes.
TL;DR: Onset times for convection induced by buoyancy forces have been measured in three aqueous systems in terms of a critical value for a time-dependent Rayleigh number as mentioned in this paper.
Abstract: Onset times for convection induced by buoyancy forces have been measured. Results on three aqueous systems are summarized in terms of a critical value for a time-dependent Rayleigh number. Because of the presence of minute traces of unavoidable surface-active contaminants, a ‘free’ water surface behaved as if it were inflexible and laterally rigid so far as determining first convective motion was concerned. The form of the onset motion was observed with schlieren photography for both top and side view. The pattern at onset was frequently in the form of plunging rings. Surface effects were demonstrated with an organic liquid layer in which onset times were measured for convection driven by surface tension gradients as well as by buoyancy forces. The data are compared with some recent predictions of linear stability analyses.
TL;DR: In this article, contact angles of a variety of hydrophobic liquids were measured on clean surfaces of borosilicate glass, quartz, and sapphire at 20°C with the RH at 0.6% and 95%.
TL;DR: In this article, a closed-form expression for the non-linear development of these long surface waves is obtained and it is shown that in the neighbourhood of the neutral curve an exponentially growing infinitesimal disturbance may develop into supercritically stable wave motion of small but finite amplitude if the surface tension of the liquid is sufficiently large.
Abstract: The linearized problem of the instability of a layer of liquid flowing down an inclined plane was formulated by Yih (1954) and was solved by Benjamin (1957). It was found that the instability of such a film flow is initially due to long surface waves of infinitesimally small amplitudes. In the present study, a closed-form expression for the non-linear development of these long surface waves is obtained. It is shown that in the neighbourhood of the neutral curve an exponentially growing infinitesimal disturbance may develop into supercritically stable wave motion of small but finite amplitude if the surface tension of the liquid is sufficiently large. Theoretically obtained amplitudes of such waves are consistent with Kapitza's (1949) observation. The approach used in this analysis is a modification of the method used by Reynolds & Potter (1967), who extended the method of Stuart (1960) and Watson (1960) in their study of the non-linear instability of plane Poiseuille and Poiseuille-Couette flow.
TL;DR: In this paper, the surface tension of transition metals is computed as a function of the filling of the d band in the tight binding limit, using an expansion of the density of states in its moments.
TL;DR: In this article, the authors investigated the impact of dynamic contact angles on the rate of surface tension at high processing speeds and found that a maximum dynamic contact angle is reached at relatively low wetting rates.
Abstract: To achieve high strength and chemical resistance in glass-reinforced plastics, it has been found essential to have a good bond between matrix and reinforcement. To obtain this bond it is necessary that good wetting of reinforcement by matrix must occur at some stage in the production cycle.
Modern process developments have reduced the time during which wetting can occur to a few seconds in continuous sheeting manufacture. The wetting stage of this process has been investigated by the observation of dynamic contact angles. The rate of wetting has been found to be controlled by liquid flow and not surface tension at high processing speeds. Breakdown of this flow and intermittent wetting have been observed directly.
When low energy surfaces are wetted by water, a different limiting factor is found. It is observed that a maximum dynamic contact angle is reached at relatively low wetting rates. It is suggested that these maximum angles offer a new means of assessing Zisman's ‘critical surface tension’ (γc) and by an extension of the technique may enable values of spreading pressure (π) to be measured.
TL;DR: The average surface tension of the tears of six human subjects was found to be two-thirds that of water.
Abstract: The average surface tension of the tears of six human subjects was found to be two-thirds that of water. The experimental method involved the use of a scleral contact lens which contained a circular tear collecting trough. Surface tension measurements using a fine wire ring were carried out while the contact lens rested on the subject's eyes.
TL;DR: In this article, the velocity of spreading of a liquid drop over a flat surface is predicted to depend on the product of three factors (1) a scaling factor, (γ/η1Ro), where Ro is the initial radius of curvature, (2) cosθ∞.
Abstract: Theoretically, the rate of capillary penetration of a polymer melt into a slit, a model for a surface irregularity, has been shown to depend on γcosθ/η) where γ refers to the surface tension of the liquid, η its viscosity and θ a time-dependent contact angle. Analytical expressions relating the depth of penetration with time have been experimentally verified by observations of the penetration of molten polyethylene and poly-(ethylene-vinyl acetate) into aluminum channels. Values of η, calculated from the observed data, agree closely with independent determinations of this material parameter. A theoretical treatment has also been developed which describes the velocity of spreading of a liquid drop over a flat surface. Flow equations for the flow of free films were adapted for this purpose. The spreading velocity is predicted to depend on the product of three factors (1) a scaling factor, (γ/η1Ro), where Ro is the initial radius of curvature, (2) cosθ∞. (l-cosθ/cosθ∞) where θ∞ refers to the equilib...
TL;DR: In this article, surface thermodynamic quantities have been calculated as functions of temperature between 0°K and the melting temperature for the noble gas solids Ne, Ar, Kr, and Xe.
Abstract: Surface thermodynamic quantities have been calculated as functions of temperature between 0°K and the melting temperature for the (111), (100), and (110) surfaces of the noble‐gas solids Ne, Ar, Kr, and Xe. The method of calculation differs from the methods used in previous treatments of surface thermodynamic functions in that the atomic vibrations are taken into account, and the vibrational frequencies are properly calculated rather than obtained from a Debye model or an Einstein model. The quantities calculated are the static surface energy, vibrational surface energy, surface entropy, vibrational surface free energy, and surface specific heat. In addition, a surface frequency‐distribution function f8(ω) has been calculated; f8(ω) is positive at low frequencies, because of the presence of surface modes of vibration, and negative at higher frequencies. This behavior of f8(ω) produces a narrow peak in the graph of the surface specific heat as a function of temperature.
01 Mar 1969
TL;DR: In this paper, the influence of temperature and added electrolytes on the dynamic surface tension of sodium dodecyl sulfate solutions was examined with the oscillating jet method, and it was shown that an increase in temperature increased the initial rate of surface tension lowering but had little effect at longer times.
Abstract: The influence of temperature and added electrolytes on the dynamic surface tension of sodium dodecyl sulfate solutions was examined with the oscillating jet method. An increase in temperature increased the initial rate of surface tension lowering but had little effect at longer times. Added electrolytes increased the rate at longer times but had little effect on the initial rate of surface tension lowering. Bivalent cations exerted greater effect than monovalent ones.
TL;DR: In this article, the authors measured the capillary length for the interface between the coexisting phases in the vicinity of the critical consolute temperature of mixtures of cyclohexane and methanol.
Abstract: We have measured the capillary length for the interface between the coexisting phases in the vicinity of the critical consolute temperature of mixtures of cyclohexane and methanol. The data on the capillary length a = 0.250 (Tc − T)0.44±0.02cm were combined with values of the difference in density Δρ between the coexisting phases calculated from the coexisting compositions to obtain the interfacial tension σ = a2Δρg / 2 = 100(1 − T / Tc)1.23 ± 0.05erg/cm2. Our measurements of σ for this system combine with the only existing measurements of the effective thickness of a critical interface in a new test of theories of critical interfaces. Data include 0.09 < Tc − T < 9°C.
01 Sep 1969
TL;DR: In this paper, the variations of density and sonic velocity with gas content have been calculated for a liquid containing gas bubbles, taking liquid compressibility and surface tension into account, the effects of pressure and bubble size have been assessed.
Abstract: The variations of density and sonic velocity with gas content have been calculated for a liquid containing gas bubbles. Taking liquid compressibility and surface tension into account, the effects of pressure and bubble size have been assessed. Particular attention has been focused on air-water mixtures, and very good agreement has been obtained with the limited amount of experimental data available.
TL;DR: In this paper, the adsorption of 3-pentanol, chloroform, cyclohexanol, cyclomethane, cyclopentanol, and cyclophexanone at the perchloric acid solution interface has been studied.