Wetting of surfaces

Wetting agents. These facilitate the wetting of surfaces and aid colloidal stability without foaming. Naphthalene sulphonate/formaldehyde is the most common wetting agent. 

The difference yg s - y, s is known as the wetting tension. If the value lies above zero wetting will take place. In actual practice wetting of surfaces by aqueous solutions is of particular interest. But the opposite case—namely, wetting by oil—is often important too. 

Wetting is an absolute condition for detergency. However, wetting plays an important role in other applications as well. A special case is the penetration of fluids in porous material. That may be a bundle of fibers in the dying process or the stone matrix in enhanced oil recovery. One of the steps of lubrication is wetting of surfaces by lubricant liquids. Because other conditions must also be considered, the use of phosphorus-containing surfactants is beneficial. 

The wetting of surfaces by adhesives can be described by two activities (1) a lateral spreading of the film and (2) a penetration of the fluid adhesive into the surface cavities that are characteristic of the inherent surface roughness. The first activity is controlled by the relative surface energies of the adhesive and substrate as explained above. The second activity is controlled mainly by the viscosity of the adhesive and the time it is in the liquid state. 

Rosenholm, J. B. (2007), Wetting of surfaces and interfaces A conceptual equilibrium thermodynamic approach, in Colloid Stability The Role of Surface Forces, Part II,Tharwat F. Tadros Colloids and Interface Science Series, Vol. 2, Wiley-VCH, Weinheim. 

Table XII. Critical Surface Tensions of Wetting of Surfaces Coated with Abhesive Films [106]...

As previously noted, the primary use for this elastomer has been as solvent-based adhesives and sealants. Solvent-based products are losing market share to water-based poly-chloroprenes, to other polymer types such as acrylics and polyurethanes, and to hot melt adhesives. However, where the processing facility is able to contain the vapor emissions, a solvent-based adhesive or sealant is preferred because of better wetting of surfaces, faster drying, and higher performance of the cured or dried product. Many rubber bonding... 

The contaminants may be deposited on the surfaces of the materials in the form of anhydrous or hydrated species. Some pollutants, like CO2, SO, NO, and HCl, are typical of urban and industrial areas, give rise to acid rains, and might contribute to the cathodic processes, while others, such as chlorides, are typical but not exclusive of marine and coastal areas and give rise to hygroscopic salts that increase the duration of wetting of surfaces, increase the conductivity of solutions, and make less protective the corrosion products. Some others, such as the sulfides, which can result from microbiological activity, alter the composition of the corrosion products, their protective capability, and the nobility of the metal often they are semiconductors, depolarize the cathodic process of hydrogen evolution, and may be oxidized to sulfuric acid by bacteria. Ammonia alters the composition of corrosion products and the solubility of metal ions it has particularly drastic effects on copper alloys and their corrosion forms. In the transport of these contaminants toward the surfaces, an important role is exerted by the wind and by the orientation of the surfaces, which can promote or hinder the washout by the rains. 

Water is a liquid of high surface tension and is obviously not suitable for wetting of surfaces. Use of water-borne paints would have been very limited had it not been possible to use surfactants in the formulation. A good surfactant reduces the surface tension of water down to 28-30 mN/m, i.e. to the same range as that of the organic solvents used in paints and lacquers. 

Wetting of surfaces by oil-based paints by causing the spreading of the paint, and thereby ensuring no beading of the paint drops on the surface... 

Intimate interfacial contact is promoted by the wetting of surfaces by a fluid adhesive which also displaces air from the surface if it has low viscosity prior to setting. This is the major characteristic of crazy glue that makes it so effective. 

N. R. Bernardino, V. Blickle, and S. Dietrich, Wetting of surfaces covered by elastic hairs, Langmuir, 26, 7233-7241 (2010]. 

MD and Monte Carlo simulations of the wetting of alumina nanochanneis by thermoplastic polymer melts have investigated the effect on wetting of surface functionalization and channel diameter. It was found that the flow rate of the pol5mier inside the nanochanneis was greatly increased when the pol5mier was... 

In recent years, therefore, development of rigid and elastic sealants on the basis of metals and ceramics was initiated. By using multiphase materials, one can adjust the elastic properties and wetting of surfaces in contact. More details concerning the various sealing materials under study today may be found in a review by Fergus (2005). 

Brush Brushing action provides good wetting of surface, resulting in good adhesion. Cost of equipment is lowest. Poor thickness control not for precise applications. Coating of individual components, spot repairs, or High labor cost. maintenance. ... 

Considering moisture, it is hard to quantify it in its incidence (as considering humidity or wetness of surface microclimates), even harder in its prediction (incorporating radiation and temperature interactions) and hardest in its action on materials ageing ([4], p. 852f). Therefore, for the ViPQuali project, materials and scenarios were chosen, for which moisture influence should not play a major role. Thus, only temperature and irradiance have to be considered, in the concept of DRF. 

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