Showing papers on "Contact angle published in 1979"
01 Jan 1979
TL;DR: In this paper, it is shown that the mutual interaction between the three materials in the immediate vicinity of a contact line can significantly affect the statics as well as the dynamics of an entire flow field.
Abstract: A contact line is formed at the intersection of two immiscible fluids and a solid. That the mutual interaction between the three materials in the immediate vicinity of a contact line can significantly affect the statics as well as the dynamics of an entire flow field is demonstrated by the behavior of two immiscible fluids in a capillary. It is well known that the height to which a column of liquid will rise in a vertical circular capillary with small radius, a, whose lower end is placed into a bath, is given by (2(j/apg) cos (), where (j is the surface tension of the air/liquid interface, f) is the static contact angle as measured from the liquid side of the contact line, p is the density, and g is the magnitude of the accelera tion due to gravity.! Thus, depending on the value of the contact angle, e, which is a direct consequence of the molecular interactions among the three materials at the contact line, the height can take on any value within the interval [ 2(J/apg, 2(J/apg]. In a sense, the influence of the contact angle is indirect: the contact angle, in capillaries with small radii, controls the radius of curvature of the meniscus which, in turn, regulates the pressure in the liquid under the meniscus. It is this pressure that determines the height of the column. In a similar manner, the dynamic contact angle can influence the rate of displacement of tbe meniscus through the capillary. The pressure drop
1,169 citations
01 Jan 1979
TL;DR: In this paper, the authors investigated how the structure of a solid surface affects the contact angle that a liquid forms on the solid, and the level of structure considered there included features that are not macroscopically observed, such as microheterogeneities, or minute peaks, pits, hills, and grooves.
Abstract: The previous chapter was largely theoretical, in that it dealt with the interpretation of contact angle results in terms of solid surface energies. It also delved into the question of how the structure of a solid surface affects the contact angle that a liquid forms on the solid. The level of structure considered there included features that are not macroscopically observed, such as microheterogeneities, or minute peaks, pits, hills, and grooves in various geometries. Their existence may be inferred from certain observations, such as contact angle hysteresis, and sometimes they can be observed directly, e.g., with the optical or electron microscope.
314 citations
TL;DR: In this paper, a correlation is suggested for available experimental measurements of the advancing dynamic contact angle measured through the liquid phase during the displacement of a liquid-gas interface through a glass capillary tube.
300 citations
TL;DR: In this paper, it was shown that the contact angle formed by a drop of liquid varies with drop size, below a critical diameter which is probably a function of the nonuniformity of the solid surface.
283 citations
TL;DR: The adsorption of water vapor on smooth crystalline quartz at pressures close to saturation has been determined by ellipsometry, particular attention being paid to excluding gel layers and contamination as discussed by the authors.
232 citations
TL;DR: In this paper, the authors derived expressions relating the geometric and thermodynamic properties of highly concentrated, monodisperse emulsions to the volume fraction of the dispersed phase for the model of infinitely long cylindrical drops.
178 citations
TL;DR: In this article, the dispersion and polar components of the hydrated solid surface free energy and the solid-water interfacial free energy were derived for poly(hydroxyethyl methacrylate-methoxyethyl methACrylate) copolymers of varying composition and equilibrium water contents.
168 citations
01 Jan 1979
TL;DR: There is a need to go beyond phenomenology, and some fundamental questions about solid surfaces come up, and the problem of hysteresis must be given explicit consideration.
Abstract: This chapter, and the following one by Neumann and Good, deal with the measurement of contact angles in three-phase systems. The contact angle is, intrinsically, a macroscopic property, and one that should be amenable to a phenomenological treatment, e.g., to measurement without regard to its thermodynamic or microscopic interpretation. But inevitably, the desire for a thermodynamic and molecular interpretation arises. In addition, some fundamental questions about solid surfaces come up, and the problem of hysteresis must be given explicit consideration. So there is a need to go beyond phenomenology.
117 citations
TL;DR: The theory of equilibrium liquid surfaces is reviewed from the macroscopic (thermodynamic) and microscopic (statistical) points of view in this paper, where the Gibbs scheme is used to describe the surface thermodynamics.
Abstract: The theory of equilibrium liquid surfaces is reviewed from the macroscopic (thermodynamic) and microscopic (statistical) points of view. Although emphasis is placed on the surface tension, other surface thermodynamic quantities are treated, especially the contact angle and work of adhesion. The Gibbs scheme is used to describe the surface thermodynamics. The equivalent hydrostatic approach, the curvature dependence of the surface tension and its relation to other surface quantities are presented. The effect of solid surface topology on the contact angle is discussed, together with the controversial Young's equation. Good's and Fowkes' theories are described and criticised from the statistical point of view. The surface tension theories for simple liquids (Kirkwood and Buff), simple metals (Evans) and solid-fluid interphases (Navascues and Berry) are deduced from a single statistical mechanical formalism. The van der Waals theory of the liquid vapour interphase is presented. Thermodynamic perturbation theory for the interphase (Toxvaerd, Abraham) and the analysis of the free energy density as a functional of the interphase density (Yang, Flemming and Gibbs) are discussed.
108 citations
15 Mar 1979
TL;DR: In this article, it has been shown that the formation of destabilizing surface tension gradients is not a necessary condition for antifoam behavior and that the critical condition for hole formation is dependent upon contact angle and particle shape.
Abstract: It has been shown that the presence of PTFE particles may reduce the amount of foam which can be generated by vigorous shaking of surfactant solutions. PTFE is an inert and hydrophobic material. The experiments have therefore demonstrated that the formation of destabilizing surface tension gradients is not a necessary condition for antifoam behavior. Simple calculations have demonstrated that particles of hydrophobic material present in thin films may in principle spontaneously dewet to form a hole which would necessarily lead to film rupture. The critical condition for hole formation is shown to be dependent upon contact angle and particle shape. Particle size is an implicit consideration in that the smallest dimension of the particle must be approximately equal to the film thickness before hole formation can occur. This antifoam mechanism is shown to be consistent with all the experimental observations concerning the effect of PTFE particles on the foamability of surfactant solutions.
92 citations
01 Mar 1979
TL;DR: Utilization of the thermodynamic prediction that cellular adhesion should become independent of the surface tension of the substrate when the surface tensions of the cells and that of the suspending medium are equal leads to a value of thesurface tension of neutrophils of 69.0 erg/cm2,† in excellent agreement with the value obtained from contact angles measured on layers of cells.
Abstract: Adhesion of leukocytes and platelets to solid substrates of different surface tensions and hence different wettability is studied from a thermodynamic point of view. A simple thermodynamic model predicts that cellular adhesion should increase with increasing surface tension of the solid substrate if the surface tension of the medium in which the cells are suspended is lower than the surface tension of the cells. If the surface tension of the suspending medium is higher than that of the cells, the opposite behavior is predicted. These predictions are borne out completely by neutrophil adhesion tests, where the surface tension of the aequeous suspending medium is varied by addition of dimethyl sulfoxide (DMSO). Platelet adhesion experiments also confirm these predictions, the only difference being that surface tensions of the suspending medium above that of the platelets cannot be realized, owing to exudation of surface active solutes from the platelets. Utilization of the thermodynamic prediction that cellular adhesion should become independent of the surface tension of the substrate when the surface tensions of the cells and that of the suspending medium are equal leads to a value of the surface tension of neutrophils of 69.0 erg/cm2,† in excellent agreement with the value obtained from contact angles measured on layers of cells.
Patent•
02 Nov 1979
TL;DR: In this paper, a release layer is kept in contact with the adhesive layer over a given area to form a composite or integral layer thereof as by extrusion coating, and a reinforcing interlayer is used to increase the adhesion between the release layer and a backing substrate.
Abstract: Pressure sensitive adhesive products or articles having one or more release layers and a pressure sensitive adhesive layer, said one or more release layer comprising a polyolefinic elastomer having a shearing modulus of less than 2.0×10 8 dyne/cm 2 and surface wettability expressed in terms of an equilibrium contact angle of more than 55° with respect to a standard liquid, and said adhesive layer being composed mainly of a polyacrylate. To increase the adhesion between the release layer and a backing substrate, a reinforcing interlayer may be used. As the release layer, a mixture of the polyolefinic elastomer and polyethylene may be used. The release layer is then kept in contact with the adhesive layer over a given area to form a composite or integral layer thereof as by extrusion coating.
TL;DR: In this article, the feasibility of new solid/liquid separation processes, such as solids removal from oil and certain tertiary oil recovery techniques, can be evaluated by a thermodynamic stability analysis of possible liquid-liquid-particle configurations.
Abstract: The feasibility of new solid/liquid separation processes, such as solids removal from oil and certain tertiary oil recovery techniques, can be evaluated by a thermodynamic stability analysis of possible liquid-liquid-particle configurations. The thermodynamic stability and hence feasibility of two possible liquid-liquid-particle separation process is predicted by use of a free energy analysis. Stability is shown to depend primarily on droplet/particle size ratio (n) and three phase contact angle (θ). Stability criteria are presented which can be applied to many particle and liquid separation processes.
TL;DR: In this article, the nucleation of gas bubbles from supersaturated solutions of nitrogen in water and ethanol-water mixtures has been studied on two metal surfaces, where a decrease in contact angle decreases the population of bubble nucleation sites by reducing the effective radii of individual sites.
TL;DR: This study indicates that the Wilhelmy balance has been an unfortunate choice of instrument for studying DPL films whose surface tensions are appreciably higher than previously estimated.
Abstract: 1. The surface properties of over 250 films of diplamitoyl lecithin (DPL) and Tween 20 on distilled water have been investigated using two different surface balances simultaneously, the Wilhelmy balance, popular in physiological studies, and the Du Nuoy ring method whose readings are independent of contact angle. 2. Using concentrations of DPL ranging from 0.08 to 1.90 microgram cm-2 on a Langmuir trough where the pool area was cycled from 100 to 27.5% of maximum, the Wilhelmy balance registered virtually the same force per wetted perimeter as the ring method for both pure water and Tween 20, but appreciably lower values for DPL over the whole cycle. 3. The above differences can be explained on the basis of a significant (45-70 degrees) contact angle, a surface property also demonstrated photographically and by direct measurement. 4. Contact angle was shown to vary with pool area, a relationship exhibiting hysteresis. 5. This study indicates that the Wilhelmy balance has been an unfortunate choice of instrument for studying DPL films whose surface tensions are appreciably higher than previously estimated.
01 Nov 1979
TL;DR: A simple apparatus which allows simultaneous estimation of the drop volume and the radius of the contact circle at the liquid/solid interface is described, and tests of the method for two systems are reported.
Abstract: The contact angle (θ) of a sessile liquid drop on a horizontal solid surface can be calculated from the drop volume and the radius of the contact circle at the liquid/solid interface. A simple apparatus which allows simultaneous estimation of these two parameters is described, and tests of the method for two systems are reported. The first system is a 3.25 mole liter−1 solution of 1-propanol in water on paraffin wax. The advancing (θa) and receding (θr) contact angles at 20°C are found to be (59.5 ± 1.0)° and (54.3 ± 0.3)°, respectively, in good agreement with the literature values and those found by direct measurement. The second system chosen is cyclohexane (a volatile liquid) on cleaved mica at 20°C. Two mica sheets were used. Mean contact angles of cyclohexane on the first mica sheet are θa = (7.45 ± 0.10)°, θr = (6.99 ± 0.12)°. For cyclohexane on the second sheet the mean contact angles are θa = (6.48 ± 0.31)°, θr = (5.56 ± 0.06)°. The difference between advancing and receding contact angles is statistically significant (P < 0.01) for both sheets. Other methods of comparable accuracy exist for θ ⪆ 30°, but the accuracy of most of these methods diminishes rapidly if θ ⪅ 30°. If calculation of the contact angle from the spacing between interference fringes is not appropriate, then estimation from drop volume and contact circle radius becomes the method of choice if θ <~ 30°.
01 Apr 1979
TL;DR: A survey of over 300 manufacturers produced over 100 replies as discussed by the authors, half of them offered some 100 products deemed worth testing, and further ideas appeared among the 100 abstracts presented in the survey.
Abstract: : Icing impairs operation of helicopters and other aircraft, antennae, power and communication lines, shipping and superstructures, canal locks, etc. Prevention or easier removal of icing requires reduction of its adhesion strength. Literature study shows that adhesion results from secondary (van der Waals) forces yet exceeds normal cohesive strengths. It depends on free surface energy, low contact angle, good contact and wetting, cleanliness, and texture. Modes of adhesion testing are briefly discussed. Poor adhesion occurs with low energy surfaces or contaminants, e.g. hydrocarbons, fluorocarbons, waxes, oils, etc., particularly when textured or porous. The resulting low contact angle, poor wetting and occlusion of air at the interface weaken the bond or provide stress loci which can initiate cracks and failure. Coefficient of expansion differences may help in release of ice. Further ideas appear among the 100 abstracts presented. A survey of over 300 manufacturers produced over 100 replies. Half of them offered some 100 products deemed worth testing. These are listed with addresses and contacts.
TL;DR: In this article, a model for the structure of NB films is proposed according to which the adsorbed DS− ions with their counterions form a two-dimensional square lattice at each film surface, and the interaction free energy of the NB films can be explained by taking into account the electrostatic interactions between the discrete ions in the two opposing surface lattices.
TL;DR: Findings show that DPL has unusual surface properties in reducing surface tension yet decreasing wettability, i.e. acting as an anti-wetting agent.
TL;DR: The pendent-drop method for measuring surface and interfacial tensions is absolute, requires only small volumes of liquids, is readily amenable to temperature control, does not require detachment, and does not depend upon the contact angle as discussed by the authors.
TL;DR: Preexposure to proteinaceous solutions had a pronounced effect, increasing the lipid uptake by the hydrogels, with the exception of PGMA, which appears to support the minimum interfacial free-energy hypothesis of biocompatibility.
Abstract: Radiochemical techniques were applied to determine protein and lipid uptake by acrylic hydrogels. The water wettability of these gels was previously obtained by using contact angle goniometry and was found to depend mainly on the composition of the polymer matrix but not on the equilibrium water content. Three hydrogels, poly(hydroxyethyl acrylate), poly(glyceryl methacrylate), and poly(acrylamide), had approximately the same equilibrium water content, therefore the same approximate penetrability with respect to protein. The uptake of both the protein (bovine serum albumin) and the lipid (cholesteryl oleate) appeared to be directly related to the water–gel interfacial tension, whereas the ease of removal was inversely related to water wettability. A cationic preservative, benzalkonium chloride, increased the protein uptake somewhat for two of the hydrogels. Preexposure to proteinaceous solutions had a pronounced effect, increasing the lipid uptake by the hydrogels, with the exception of PGMA. The results obtained appear to support the minimum interfacial free-energy hypothesis of biocompatibility.
TL;DR: The surface free energy of unswelled polystyrene was estimated from the contact angles and the swelling results, using an equation which had previously been proposed by Good as discussed by the authors, and the value of γs is estimated to be 42±2 ergs/cm2.
Abstract: The contact angle of CH2I2, α-bromonaphthalene and aniline on crosslinked polystyrene has been measured. The polymer was swollen for as long as 60 days in the liquid whose contact angle was to be measured. The surface free energy, γs, of unswelled polystyrene was estimated from the contact angles and the swelling results, using an equation which had previously been proposed by Good. The value of γs is estimated to be 42±2 ergs/cm2.
TL;DR: In this paper, a reasonable degree of agreement between the two techniques is shown, despite the assumptions and variables involved, and the two approaches are shown to have similar properties and a similar accuracy.
01 Mar 1979
TL;DR: In this article, the problem of the behavior of a bubble attached to a solid wall was solved numerically by the variational method, in which the viscosity and compressibility in the liquid are neglected.
Abstract: The problem of the behavior of a bubble attached to a solid wall was solved numerically by the variational method, in which the viscosity and compressibility in the liquid are neglected. The effects of the surface tension and the contact angle on the collapsing bubble were taken into account. As a result, it was clarified that for the contact angle α < 90 ° the projecting part of liquid advancing against a solid wall was formed in the collapsing process regardless of the amount of gas in the bubble and the bubble size, and that the effects of the Weber number and the contact angle on the bubble shape were large, while the effect of amount of gas in the bubble was small.
Patent•
24 Jan 1979
TL;DR: In this article, a film, sheet, or molded article (A) of an organic polymer, e.g., polyethylene or epoxy resin, is placed in a plasma reaction tube, and evacuated.
Abstract: PURPOSE: To provide a film or sheet material having improved hydrophobic nature, chemical and abrasion resistance, hardness, and low adhesion, by introducing fluorine into the surface region of an organic polymer in contact with a fluorine-containing plasma. CONSTITUTION: A film, sheet, or molded article (A) of an organic polymer, e.g. polyethylene or epoxy resin, is placed in a plasma reaction tube, and evacuated. CF 4 of several hundreds of Pa is introduced into the tube, and a radiofrequency power is applied to generate a plasma. Preferably, the plasma is formed from a fluorinated hydrocarbon or fluorocarbon. The plasma-treated A has properties similar to those of polytetrafluoroethylene. EFFECT: The treated epoxy resin film has a contact angle with water of 110° and a dispersion force component of surface free energy of 36mJ/m 2 compared with 110° and 18mJ/m 2 of the intreated film respectively. COPYRIGHT: (C)1980,JPO&Japio
TL;DR: In this paper, a free energy analysis for cylindrical particles was developed for the surface of which consists of alternate types of strips of intrinsic contact angles, and it was shown that for any such particle there may be a stable and an unstable equilibrium state on each of the two types of surfaces.
TL;DR: In this paper, the effect of surfactants such as anion-active sodium dodecyl sulphate (NaDS) and cation-active cetyltrimethylammonium bromide (CTAB) on the contact angles formed on the quartz surface by 0,1 N NaCl aqueous solution at different pH were measured.
Abstract: The contact angles formed on the quartz surface by 0,1 N NaCl aqueous solution at different pH were measured. The effect of surfactants such as anion-active sodium dodecyl sulphate (NaDS) and cation-active cetyltrimethylammonium bromide (CTAB) was investigated. The results are interpreted in terms of the Frumkin-Derjaguin theory of wetting.
TL;DR: In this paper, Ellipsometrically determined adsorption isotherms are reported for ethanol, propanol, butanol, amyl alcohol, n -hexane, and diethyl ether on optically smooth polyethylene at 20°C.