Paint systems surface tension

Low surface tension (poor wettability ) may be a factor, with apparent repulsion of the paint and prevention of its rapid, even spread over the whole surface test inks of different values are available so that wettability can be assessed in advance with samples of the items concerned for satisfactory use with paints based on organic solvents, surface values of greater than 50 mN m 1 are desirable, and for water-based systems values greater than 70 mN m. ... 

For self-releasing systems the presence of an IMR agent on the surface of the part, which makes It self-releasing, also lowers the value of the solid s critical surface tension, making It less wettable by the paint, than If It were free of the IMR surface coating. This problem, however, can be solved by either one of two ways (1) by the addition of solvent to the paint formulation that... 

Colloidal dispersions and other related systems are present in many applications, e.g., in paints and coatings and detergents. Here, phase equilibrium and surface phenomena are equally important. A unified representation of such phenomena, e.g., of adhesion phenomena and liquid-liquid equilibria with the same model/concepts is of interest. Thermodynamic models can be used to calculate certain surface properties such as surface tension. hi addition, properties such as the solubility parameters can be equally well employed for bulk and surface thermodynamic properties. ... 

Two other effects due to surface tension are the capillary rise of liquids in small tubes and porous wicks (without which kerosene lanterns or copper sweat-solder fittings wouid not work at all) and the tendency of jets of liquid to break up into drops (asj from a garden hose or diesel fuel injector). Surface tension effects are very important in systems involving large surface areas, such as emulsions (mayonnaise, cold cream, water-based paints) and multiphase flow through porous media (oil fields). We discuss the effects in Chap. 17 see also Refs. 4 and 5. 

If both E and are positive, the defoamer penetrates into the foam lamella and spreads across the surface. This creates interfacial tension differences that destabilize the lamellae and cause the foam to collapse. In simple terms it can be said that defoamers act because of their controlled incompatibility with the paint system. If a defoamer is too compatible its defoaming effect is not sufficient, if it is too incompatible film defects occur (e.g., gloss reduction, formation of craters). 

Lanco A1601 surface tension reducer Arcosolv PE Arcosolv PM Arcosolv PNB Arcosolv TPM DeWET SDO-70PG DeWET SDO-75E Lodyne Raybo Powder Additive 110 surface tension reducer, 1-coat systems TEGO GlldeA115 surface tension reducer, acrylate-isocyanate paints TEGO GlldeA115 surface tension reducer, acrylics Nopco 1186A... 

In a recent case study (see Svendsen et al, 2007 and also Problem 6.1), in collaboration with a paint company, the adhesion of six different epoxies-silicon systems has been studied. These paints are used in marine coating systems. Some epoxies showed adhesion problems in practice while others did not. The purpose of the study was to understand the origin of these problems and whether adhesion could be described/ correlated to surface characteristics, e.g. surface tensions. An extensive experimental study has been carried out including both surface analysis (contact angle measurements on the six epoxies, surface tension of silicon at various temperatures, atomic force microscopy (AFM) studies of the epoxies), as well as measurements of bulk properties (pull-off adhesion tests and modulus of elasticity). Theoretical analysis included both estimation of Zisman s critical surface tensions and surface characterization using the van Oss-Good theory. 

Circulation studies of water-borne metallic basecoats demonstrate a few reasons why specular reflectance is lost during circulation. The flow induced stress of circulation reduces flake size and produces cycles in liquid surface tension. Surface tension in turn controls amount of picture framing and film thickness. If rust is present in the circulation system, it can react with the paint resins, creating gel lumps which under circulation trap the metal flake hindering flake alignment. Smaller flakes, thicker film thickness and poor aluminium alignment all reduce specular reflectance within the sprayed basecoat paint film [109-115]. 

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