Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Wettability”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources
PubMed1998

Influence of Surface Wettability on Adsorption Isotherms of Water Vapor

Using an exponential form of an isotherm of adsorption the excess surface free energy of a solid surface covered with an adsorption or wetting film Deltagammasv was calculated on the basis of Gibbs equation starting from the state of an infinitely thick film. Isotherms of adsorption and of excess surface free energy were calculated for different values of two parameters that characterize the range of action of surface forces and corresponding decay length. In the case of partial wetting of a solid surface, isotherms consisting of two exponential terms were used, as was proposed earlier by A. Adamson. Equilibrium contact angles that are formed with droplets of bulk liquid were calculated using the Frumkin-Derjaguin approach in dependence on the parameters of isotherms. Calculations of contact angles that are formed between convex capillary menisci in thin pores, at relative vapor pressure lower than 1, have shown that a transition from partial wetting of a lone solid surface (at p/ps = 1) to complete wetting in thin pores (at p/ps < 1) may occur. Corresponding threshold values of relative vapor pressure and pore radii were calculated. In the case of complete wetting, corrections for capillary pressures that arise due to formation of a transition zone between wetting films and curved meniscus surfaces were estimated. The calculations are limited by the values of relative vapor pressure near saturation when thick enough wetting films are formed on pore surfaces. Due to the application of model isotherms with some adopted parameters, the results obtained are qualitative in nature. However, the methods of calculation developed for the excess free energy of solid surfaces covered with thin adsorption of thicker wetting films and of contact angles outside and inside thin pores may be of general interest. Copyright 1998 Academic Press. Copyright 1998Academic Press

Journal Article↗
PubMed1998

Acid-Base Approach to Latex Particles Containing Specific Groups Based on Wettability Measurements.

Polar properties of latex particles containing specific groups with various surface charge densities were examined from contact angle measurements using "old" polar/dispersive models. It was determined that the Fowkes approach is quite sufficient for classifying our functionalized polystyrene latices. The pertinence to our systems of the acid-base approach, which has a more pronounced chemical background, was then investigated, and the strong dependence of the acid-base parameters (gamma plus sign in circle, gammaTheta) on the acid-base scale chosen for the reference liquid (water) was shown. Finally, using the receding angle values revealed the outermost surface buried moieties in the latex particles, which were not seen in the advancing angle measurements. Copyright 1998 Academic Press.

Journal Article↗
PubMed1999

The 6-(10-Mercaptodecoxyl)quinoline Self-Assembled Monolayer on Gold: Spectroscopy and Wettability Investigation.

A self-assembled monolayer (SAM) with an exposed basic group has been generated by the adsorption of a novel quinoline derivative 6-(10-mercaptodecoxyl)quinoline (MDQ) on a gold surface. The structure and surface properties of the SAMs of MDQ were characterized by ellipsometry, reflection absorption FTIR (RA-IR), and contact angle titration. It was found that the quinoline moiety of MDQ forms an ordered layer on the top of the film and the alkyl chain exhibits a packing density similar to that of a monolayer of decanethiol. The molecular orientation of MDQ in SAMs was evaluated by RA-IR spectroscopy which indicates that the alkyl chain exhibits a tilting angle of 24 +/- 4 degrees with respect to the surface normal and a twisting angle of 50 +/- 5 degrees around its axis. Contact angle titration in the pH range between 2 and 12 illustrates that the surface of SAM of MDQ is less hydrophilic for acidic solution than for basic solution, which is in contrast with the previous reports on SAMs that basic groups are located at the ends of the molecules. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Atomic Force Microscopy and Wettability Study of Oxidized Patterns at the Surface of Polystyrene.

The surface properties of patterned surfaces made by a combination of photolithography and oxygen plasma treatment of polystyrene (PS) were investigated. PS and plasma-treated PS (PSox) were first characterized using X-ray photoelectron spectroscopy and the study of wetting dynamics (Wilhelmy plate method) in water and in solutions of different pH. The results indicated that the PSox surface may be viewed as covered with a polyelectrolyte-like gel, which swells depending on pH. It was then shown, using atomic force microscopy (AFM), that the adhesion force measured on PS with a silicon tip in water was higher compared with that measured on PSox. This feature allowed imaging of the oxidation patterns using the adhesion mapping mode. The origin of the pulloff force contrast, which could not be explained by combining Johnson-Kendall-Roberts theory and thermodynamic considerations, was attributed to repulsion between the tip and hydrated polymer chains present on the oxidized surface. Imaging was also performed in the lateral force mode, a higher friction being recorded on PS than on PSox. Copyright 1999 Academic Press.

Journal Article↗
PubMed2001

Wettability of Nematic Liquid Crystals.

Organic liquids such as nematic liquid crystals should wet solids with high surface energies like mica, yet they generally do not. In the model proposed here, the affinity to wet the solid in form of Hamaker forces is opposed by elastic effects due to nematic order. Results predict correctly that such liquids show small contact angles and the formation of ultrathin liquid films ahead of the bulk drops. Copyright 2001 Academic Press.

Journal Article↗
PubMed2002

Mineral matter distribution on coal surface and its effect on coal wettability.

Coal is an organic sedimentary rock composed of organic macerals and mineral matter. As it is demonstrated in this paper the discrete mineralogical nature of coal largely influences the wetting of the coal surface by water. Both advancing and receding contact angles were measured using the captive-bubble technique with an automatic bubble shape analysis software. The distribution and amount of mineral inclusions on the coal surface were determined by scanning electron microscopy and examined using the image analysis system. To determine the amount and size distribution of mineral grains, the coal surface layer, on which the contact angles were measured, was separated from the larger piece used in the measurements by microslicing. The separated surface layer was subjected to a low-temperature ashing followed by particle size analysis. As expected, a significant scatter of contact angle values was obtained for the same coal samples. Increasing the amount of mineral matter on the coal surface reduced the value of both advancing and receding contact angles. Also, the scatter of contact angle values increased with the increasing mineral matter content from about 1 to 50 wt%. The results reveal that an important factor in analysis of contact angle variation on coal surfaces is the size of the hydrophilic mineral inclusions. Both the advancing and the receding contact angles decrease with increasing size of the mineral grains. Additionally, the scatter of contact angle values increase with increasing size of the mineral matter grains. Finally, the results of fractal dimension analysis of mineral matter grains distributed over the coal surface indicate that there is no significant effect from the shape of hydrophilic mineral inclusions on both advancing and receding contact angles.

Journal Article↗
PubMed1990

Evaluation of Bactimos wettable powder, granules and briquets against mosquito larvae in Malaysia.

There was high mortality in late larval instars of Aedes albopictus (Skuse) from laboratory and field populations in the 24 h after application of three Bactimos formulations of Bacillus thuringiensis H-14. Mortalities were higher and residual effects longer in field populations than in laboratory ones. Briquets were the most effective formulation (mortality 96-100% after five weeks; 76-92% after eight weeks). Culex quinquefasciatus Say larvae were tested only against the briquet formulation. In the laboratory, 100% mortality of late instars persisted for six weeks and dropped to 48-88% after eight weeks. In the field, late instars were reduced by 62-87% after 24 h and 69-72% after one week compared to increases in an untreated population of 160% and 176% respectively.

Aedes↗
PubMed1989

Complete denture retention. Part II: Wettability studies on various acrylic resin denture base materials.

The objective of this study was to characterize in vitro selected acrylic resin denture base materials by water-contact angle measurements. The sessile drop method and the underwater-bubble method were used. The results obtained from these measurements are discussed in terms of contact angle and polymer-water work of adhesion hysteresis. On polished heat-polymerized samples this hysteresis results from the reorientation of superficial polymer chains. The combined effect of increased sample roughness and of the entrapment of water droplets in the pores of material gives rise to the highest contact-angle hysteresis observed on sand-abraded samples. On the basis of physical analysis of the mechanism involved in complete denture retention, developed in Part I of this work, it is believed that the sand-abraded material is the most convenient for the retention of the complete denture.

Acrylic Resins↗
PubMed1986

Surface modification of soft contact lenses: silanization, wettability and lysozyme adsorption studies.

The surface reactions of poly(2-hydroxyethylmethacrylate) (PHEMA) and the copolymer poly(HEMA-methacrylic acid) (PHEMA/MAA) with methyltrimethoxysilane, ethyltrimethoxysilane and phenyltrimethoxysilane have been characterized by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. A model compound, hydroxyethyl isobutyrate was synthesized and subsequently reacted with phenyltrimethoxysilane. Its FTIR spectrum was compared with the ATR-FTIR spectra mentioned above. Protein adsorption experiments showed that silanized PHEMA/MAA soft contact lenses adsorbed less lysozyme than the untreated lenses.

Adsorption↗
PubMed2005

Observation of wall wettability under imposed flow by fluorescence depolarization: dependence on surface oxygen content and degree of polymer branching.

This work was concerned with the dependence of the interfacial tension (Gamma(SL)) on surface degree of oxygen content and on polymer branching degree. The static Gamma(SL) was evaluated by contact angle (theta;(c)) and the dynamic Gamma(SL) by fluorescence depolarization of molecular probes seeded in induced flows of monoethylene glycol. The latter results were interpreted using statistical covariant analysis. Two different systems of flowing films were studied: free films flowing on the surfaces on which they impinge and films flowing inside 1-mm-thick microflow cells. The solid surfaces were polyethylene of low density, medium density, high density, and linear with low density, polypropylene, vinyl acetate co-polymer with oxygen content of 15% and 28%, borosilicate, and tin dioxide. Increase in oxygen content of the surface decreased both the static and the dynamic Gamma(SL), which demonstrated that the presence of oxygen atoms hindered wetting. Only the dynamical Gamma(SL) was sensitive to polymer branching, and it increased as branching degree decreased. This was attributed to the higher hydrogen-atom density at the surface, which favored temporary intermolecular bonds between the surface and the flowing liquid.

Journal Article↗
PubMed2005

The wettability of polytetrafluoroethylene by aqueous solutions of sodium dodecyl sulfate and propanol mixtures.

Advancing contact-angle (theta) measurements were carried out with aqueous solutions of propanol and four series of aqueous solutions of dodecyl sulfate (SDDS) and propanol mixtures at constant dodecyl sulfate concentrations equal to 1 x 10(-5), 6 x 10(-4), 1 x 10(-3), and 1 x 10(-2)M, respectively. The obtained results indicate that in the range of propanol concentrations studied there were considerable contact-angle changes, with exception of the solution series at a constant concentration value of SDDS higher than its critical micelle concentration. From the results of contact-angle measurements and application of the Gibbs and Young equations the ratio of the excess concentration of surfactant and propanol at the solid-aqueous solution interface to the excess of their concentration at the aqueous solution-air interface was calculated. From the calculations it appears that there is a straight linear dependence between the adhesion tension and surface tension of aqueous solutions of SDDS and propanol mixtures, and the slope of the line is equal to -1, which suggests that the surface excess of the SDDS and propanol mixture at the polytetrafluoroethylene-solution interface is the same as the at the solution-air interface. The extrapolation of the straight line to the point corresponding to the surface tension of the aqueous solution, which completely spreads over the polytetrafluoroethylene surface, gives a critical surface tension of wetting equal to 23.7 mN/m. On the basis of the critical surface tension and the Young and modified Szyszkowski equations it was found that in a polytetrafluoroethylene-aqueous solution of the SDDS and propanol mixture, the interface tension can be predicted by the modified Szyszkowski equation.

Journal Article↗
PubMed2005

Formation of polyelectrolyte multilayers on fibres: influence on wettability and fibre/fibre interaction.

Polydimethyldiallylammonium chloride (PDADMAC) and polystyrene sulfonate (PSS) have been used to build-up polyelectrolyte multilayers (PEMs) on chemical soft wood fibres and on SiO2 at various electrolyte concentrations. Adsorption onto SiO2 was studied using a stagnation point adsorption reflectometer (SPAR), and the adsorbed amount of PDADMAC and PSS on the fibres was determined using nitrogen analysis and Schöniger burning, respectively. The adsorption onto the two substrates was then compared. Paper testing showed that the tensile index (TI) increased by about 90% when 11 layers had been adsorbed, and that there was a correlation between the adsorbed amount and the increase in TI. It was also shown that the particular polymer present in the outermost layer significantly influenced the TI, and that PDADMAC produced a higher TI. A correlation between the adsorbed amount and the TI was also found. Individual fibres were partly treated with a PEM and analysed using a dynamic contact angle analyser (DCA) and environmental scanning electron microscopy (ESEM).

Journal Article↗