Showing papers on "Contact angle published in 1980"
TL;DR: Results show that the nondispersive-dispersive force balance at the polymer-protein solution interface, expressed by the Ip/WA d ratio, is an important factor for binding of proteins on polymer surfaces.
Abstract: Adsorption of bovine albumin, gamma-globulin and fibrinogen from phosphate buffer solution (pH = 7.5) onto several polymer films was studied using the radioiodinated proteins (125I). The kinetics of desorption of the proteinated polymer films in bovine plasma was determined. Contact angle measurements on these same polymers allowed the calculation of dispersive (WA d) and polar (Ip) components of the polymer-protein solution system. Results from these measurements show that the nondispersive-dispersive force balance at the polymer-protein solution interface, expressed by the Ip/WA d ratio, is an important factor for binding of proteins on polymer surfaces. The purity of fibrinogen and the cleaning procedures for the polymer surfaces influence the absolute values of proteins adsorbed on polymer surfaces.
200 citations
TL;DR: In this article, the influence of surface roughness on the equilibrium spreading of liquid on solids, employing well-characterized rough surface and a well-defined technique of attaining drop equilibrium.
189 citations
TL;DR: In this paper, a discharge-treated polyethylene terephthalate (PET) film has been discharge-treated under controlled conditions and the resulting surface modifications analysed via Xps (ESCA), contact angle and surface energy measurements changes in surface properties have been followed as a function of ageing time.
180 citations
TL;DR: In this article, the shapes of drops of given volume and density in contact with an inclined plate over a circular wetted area are found from the Young-Laplace equation by means of the finite element method.
173 citations
TL;DR: In this paper, surface oxides on various carbon fibres were determined after modified oxidation treatment with nitric acid and improved wetting was investigated by contact angle measurements, by surface tension measurements and by chemical analysis of the chemisorpted diamine hardener.
148 citations
TL;DR: In this article, the volume fraction φ 0 of the dispersed phase in close-packed, uncompressed emulsions is predicted as a function of the thickness of the film separating neighboring droplets, and of the contact angle between the film and its adjacent Plateau border.
138 citations
01 Nov 1980
TL;DR: In this article, the equilibrium spreading pressure of a spreading liquid or vapor on polyethylene polymers was predicted exactly by π e = 2(γ d L γ d S ) 1 2 −2γ L where γLd is the dispersion force contribution to the surface tension of the spreading liquid and γSd is a contribution to surface energy of the substrate.
Abstract: When a spreading liquid or vapor can interact with a substrate only by dispersion forces, as with alkanes on any substrate, or with any spreading liquid on saturated hydrocarbon polymers, the equilibrium spreading pressure is shown to be predicted exactly by: π e =2(γ d L γ d S ) 1 2 −2γ L where γLd is the dispersion force contribution to the surface tension γL of the spreading liquid and γSd is the dispersion force contribution to the surface energy of the substrate. A new laboratory technique is introduced for direct measurement of πe of a spreading vapor on hydrophobic solids, using the difference in contact angles of a test liquid on the solid in air and in the presence of the spreading vapor. For cyclohexane on polyethylene at 20°C πe is found to be 7.19 dyn/cm; the above equation predicts 7.15 dyn/cm. By using this new technique it is proven unequivocably that high-energy liquids such as methylene iodide and water do not adsorb or spread on low-energy surfaces such as polyethylene or polytetrafluoroethylene.
126 citations
TL;DR: In this article, the authors derived the surface tension values of the contact angle of a given contact angle with a given liquid of known surface tension using the Young's equation of state.
Abstract: From the contact angle θ determined with one liquid (of known surface tension) only, it is possible to obtain the values of the surface tensions γSV and γSL, via the equation of state (1): where the subscripts S and L stand for the solid S and the liquid L, whilst the subscript V stands for vapor. In conjunction with Young's equation (2): relation [l] yields: With the help of a computer program values for γsv (1) and for γSl (3) can be derived for different values of the contact angle 8 obtained with a liquid of given γLV
120 citations
TL;DR: In this article, the surface tension, capillary force, and total force of adhesion between unequal-size spheres are calculated as a function of liquid-bridge volume, and the mean radius of curvature is calculated by using an averaging procedure, which is simple and accurate.
96 citations
92 citations
TL;DR: In this paper, the surface composition of commercial treated and untreated fibers was compared to the real fiber surface incorporated in composites using X-ray photoelectron spectroscopy (XPS) and contact angle measurements.
TL;DR: Results show that the thermodynamics of the partitioning of a suspended particle between two immiscible liquid phases also apply to partitioning between a liquid and a solid phase.
TL;DR: In this paper, an analytical solution for the primary potential and current distribution around a spherical bubble in contact with a plane electrode is presented, and the incremental resistance caused by dilute arrays of bubbles is evaluated.
Abstract: An analytical solution for the primary potential and current distribution around a spherical bubble in contact with a plane electrode is presented. Zero at the contact point, the current density reaches only 1% of its undisturbed value at 30% of the radius from that point and goes through a shallow maximum two radii away. The solution obtained for spherical bubbles is shown to apply for bubbles having contact angles smaller than 17.5 ~ . The incremental resistance caused by dilute arrays of bubbles is evaluated.
01 Nov 1980
TL;DR: The results demonstrate the importance of van der Waals' interactions in the phase-partition process, that phase partition can be used as a direct measure of cell surface hydrophobicity, and that the equilibrium constant of phase partition is directly related to the difference in the surface energy of the partitioned particle between the two phases.
TL;DR: In this paper, the authors observed very high contact angles, in some cases approaching 90°, for aqueous films between oil droplets, stabilized by anionic surfactants in the presence of various electrolytes.
Abstract: As a result of interaction forces, the tension of a thin liquid film can be lower than the sum of the interfacial tensions of the bulk surfaces bounding the film1. To satisfy conditions of mechanical equilibrium, this reduced film tension leads to a macroscopic contact angle between the film and its associated Plateau border2. We have observed and report here very high contact angles, in some cases approaching 90°, for aqueous films between oil droplets, stabilized by anionic surfactants in the presence of various electrolytes. The contact angle is found to depend on the nature of the surfactant head group, type and concentration of counter-ion, and temperature. These contact angles have a pronounced effect on the stability, structure and rheology of emulsions.
TL;DR: The influence of surface roughness on the equilibrium spreading of liquids on aluminium and stainless steel surfaces with well-characterized rough machine finishes and a well-defined technique of attaining liquid drop equilibrium has been experimentally studied as mentioned in this paper.
Abstract: The influence of surface roughness on the equilibrium spreading of liquids on aluminium and stainless steel surfaces with well-characterized rough machine finishes and a well-defined technique of attaining liquid drop equilibrium has been experimentally studied. The surfaces were prepared under practical conditions, i.e. without rigorous purification or attempting to eliminate anisotropy or microheterogeneities in surface-free energy. Depending on the type of roughness, i.e. spiral-grooved, radial-grooved and porous, the advancing contact angle was in approximate agreement with one of the classical contact angle/surface roughness equations. Capillary channelling along machine grooves profoundly affected the spreading and wetting behaviour and was highly dependent on the orientation and texture of roughness. Although the observed spreading was generally smooth on all surfaces it was probable that microscopic surface asperities produce small-scale non-equilibrium contact line movements and are responsible for the extensive wetting hysteresis during drop retraction.
01 Nov 1980
TL;DR: In this article, the molecular configuration as a function of concentration for aqueous anionic, cationic, and nonionic surfactants adsorbed on a polycarbonate membrane is presented.
Abstract: Direct evidence is presented for the molecular configuration as a function of concentration for aqueous anionic, cationic, and nonionic surfactants adsorbed on a polycarbonate membrane. The polycarbonate surface consists of ionizable weak-acid groups with an average pK value of approximately 4. Hydrodynamic thickness, determined from filter viscometry, in conjunction with contact angle and streaming potential measurements, elucidate the adsorption mechanisms. At neutral pH, nonionic and counterion surfactant adsorption occurs in three regions. In the low-concentration region I, the surfactant lie prone to the surface. Near the CMC, region II, the surfactants stand vertical with their hydrophobic moiety exposed to the aqueous solution. Very slightly beyond the CMC, region III commences with tail-tail bilayer adsorption. Co-ion surfactant adsorption does occur, but only in region I. 34 references.
TL;DR: The Young-Laplace equation of capillarity augmented by the disjoining pressure concept of Deryagin has been used to obtain the interfacial profile in the contact line region of a finite contact angle system as discussed by the authors.
TL;DR: In this article, the critical velocity of engulfing V c of acetal, nylon-6,6, and nylon-12 particles when encountered by the solidification front of salol is reported as a function of particle size.
TL;DR: Partition coefficients in biphasic mixtures of poly(ethylene glycol) and Dextran are compared to cell surface energies obtained from contact angles of each liquid phase on cell layers and linear relationships are observed.
TL;DR: The cells appear to be highly hydrophilic during growth on a soluble substrate, and the surface free energy of the cells was calculated along with the cell-aqueous and cell-hydrocarbon interfacial tension.
Abstract: Acinetobacter calcoaceticus was grown in 11-liter batch fermentations with hexadecane or sodium citrate as the sole source of carbon. Surface and interfacial tension measurements of the microbial broth indicated that surface-active compounds were being produced only during growth on the hydrocarbon substrate. Contact angle measurements of an aqueous drop on a smooth lawn of cells in a hexadecane bath indicated a highly hydrophobic surface of the cells in the initial stages of the hydrocarbon fermentation (120° contact angle). At this stage, the entire cell population was bound to the hydrocarbon-aqueous interface. The contact angle dropped rapidly to approximately 45° after 14 h into the fermentation. This coincided with a shift of the cell population to the aqueous phase. Thus, the cells demonstrated more hydrophilic characteristics in the later stages of the fermentation. Contact angles on cells grown on sodium citrate ranged from 18 to 24° throughout the fermentation. The cells appear to be highly hydrophilic during growth on a soluble substrate. From the contact angle and aqueous-hydrocarbon interfacial tension, the surface free energy of the cells was calculated along with the cell-aqueous and cell-hydrocarbon interfacial tension. The results of these measurements were useful in quantitatively evaluating the hydrophobic nature of the cell surface during growth on hydrocarbons and comparing it with the hydrophilic nature of the cell surface during growth on a soluble substrate.
TL;DR: In this paper, a homogeneous SiOx (1.5 < x < 2.0) films prepared from the glow discharge reaction of silane or a silane derivative with an oxidant such as nitrous oxide or oxygen have shown considerable promise as dielectric layers.
TL;DR: In this article, the authors postulate that the layer of liquid immediately adjacent to the solid surface has an ordered structure similar to that of a liquid monocrystal, and this structure is fluid (zero yield point in shear) in the plane of a solid surface and presents no obstacle to an increase of the solid-liquid interfacial area.
TL;DR: In this article, the aqueous wetting properties of samples of a hydrophobic powder (griseofulvin) prepared by crystallisation, controlled precipitation, dry grinding and wet grinding have been assessed by two methods in terms of a contact angle, θ.
TL;DR: It is concluded that the data bear more relevance to the protein layer/polymer interface than to theprotein layer/solution interface, and that the contact angle technique is not a suitable technique for studying the latter on biomaterials.
Abstract: Contact angle studies have been carried out on plasma protein layers adsorbed on selected polymer surfaces under buffered saline at 37 degrees, in an attempt to demonstrate directly a recent suggestion that the interfacial free energy between such protein layers and surrounding liquid phase should be zero at equilibrium. Although an initial contact angle of 180 degrees was always obtained, the angle decayed slowly to a stationary value which varied for any one drop on each polymer surface. The stationary values could be reasonably correlated with the reversible work of adhesion predicted for each polymer/protein combination, suggesting that protein desorption from the solid surface is a dominant event in the contact angle decay process. It is concluded that the data bear more relevance to the protein layer/polymer interface than to the protein layer/solution interface, and that the contact angle technique is not a suitable technique for studying the latter on biomaterials.
TL;DR: In this article, the authors show that the rate of removal of mineral oil soils from polyester substrates by the roll-up mechanism shows a marked dependence on nonionic surfactant concentration even above the critical micelle concentration (cmc).
Abstract: The rate of removal of mineral oil soils from model polyester sub-strates by the roll-up mechanism shows a marked dependence on nonionic surfactant concentration even above the critical micelle concentration (cmc). Similarly, although the solid/water interfacial tension is observed to be constant, the equilibrium oil/water inter-facial tension in these systems consistently decreases as the nonionic surfactant concentration is increased. The dependence of removal time and oil/water interfacial tension on surfactant concentration above the cmc is most pronounced for nonionic surfactants having relatively high cmc. At a given concentration, surfactants exhibiting the lowest equilibrium oil/water interfacial tension generally provide the most effective soil removal, suggesting that the reported depen-dence of removal time on surfactant concentration is related to the commensurate lowering of the oil/water interfacial tension. Nonyl phenol ethoxylates perform exceptionally well with mineral oil on polyester substrates because of the combination of a low oil/water interfacial tension and high solid/water adhesion tension. Regardless of surfactant structure, mineral oil on Teflon FEP maintains a high contact angle in the water because the solid/oil interfacial tension is less than the solid/water interfacial tension. Oil removal in such systems occurs only by an inefficient necking and drawing process. Oleyl alcohol displays a high contact angle in the water on both Teflon FEP and Mylar substrates for reasons similar to that of mineral oil on Teflon FEP. Partial oil removal occurs from both substrates in selected built systems, presumably because a low oil/ water interfacial tension promotes necking and drawing. Given sufficient time, unremoved oils develop a liquid crystalline phase which results in slow oil removal via dispersion. Triolein soils also possess a relatively low solid/oil interfacial tension and similarly exhibt a high contact angle (in water) on both Teflon FEP and Mylar substrates in unbuilt surfactant systems. Builder addition lowers the oil/water interfacial tension and thereby prompts necking and drawing action.
TL;DR: In this article, the results indicate that an oxygen plasma roughens the surface and that oxygen is incorporated into the surface, and the degree of improvement in adhesion was dependent on the type of plasma and the treatment time.
Abstract: Plasma-treated poly-p-xylylene films have been characterized by neutron activation oxygen analysis, internal reflection (IRS) and transmission infrared spectroscopy, transmission electron microscopy (TEM), and surface contact angle measurements. The results indicate that an oxygen plasma roughens the surface and that oxygen is incorporated into the surface. Oxygen is not detected in the bulk of the sample. The infrared transmission spectra exhibited no carbonyl band, but the relative band intensities changed, indicating a change in ring substitution by a loss of chlorine in the chlorinated poly-p-xylylenes. The IRS spectra of the surface of films treated with oxygen plasma did contain carbonyl bands at 1730 and 1640 cm−1. Argon and helium plasmas generally decreased the water contact angle measured on plasma-treated poly-p-xylylene surfaces more than oxygen or nitrogen plasma treatments. Regardless of the plasma utilized, the water contact angles increased with time after the treatment but did not recover to the original level. IRS spectra of the surface of films treated with argon plasma contained carbonyl bands at 1730 and 1695 cm−1. The adhesion of a polyurethane thermosetting material to a poly-p-xylylene surface is greatly improved if a plasma treatment is used prior to the application of the polyurethane. The degree of improvement in adhesion was dependent on the type of plasma and the treatment time.