Coatings surface tension

Silieone-based surfactants offer many benefits in waterborne coatings. The coating surface tension can be modified to improve substrate wetting, in particular when trisiloxane polyethers are used, since these structures provide excellent wetting to low-energy substrates. 

Coalescence is the fusing of molten particles to form a continuous film, the first step in powder coating. Surface tension, radius of curvature, and viscosity of the molten powder control coalescence. In order to have more time available for leveling, it is desirable to have small particles, low viscosity, and low surface tension. 

Uses Wetting agent, leveling agent in cleaning products, floor finishers, sealers adhesion modifier, penetrator in water reducible inks, coatings surface tension reducer in acids, KCI, brine... 

For hquid systems these surface energies expressed in mj/m are numerically equivalent to the surface tensions in mN/m(= dyn/cm). If the adhesive is phase 1 and the release coating is phase 2, then the spreading coefficient, S, of 1 on 2 is as given in equation 2. 

Adhesion to Metals. For interaction between coating and substrate to occur, it is necessary for the coating to wet the substrate (107). Somewhat oversimplified, the surface tension of the coating must be lower than the surface tension of the substrate. In the case of metal substrates, clean metal surfaces have very high surface tensions and any coating wets a clean metal substrate. 

Increase adhesion tension. Maximize surface tension. Minimize contact angle. Alter surfactant concentration or type to maximize adhesion tension and minimize Marangoni effects. Precoat powder with wettahle monolayers, e.g., coatings or steam. Control impurity levels in particle formation. Alter crystal hahit in particle formation. Minimize surface roughness in milhng. 

The majority of particles in the atmosphere are spherical in shape because they are formed by condensation or cooling processes or they contain core nuclei coated with liquid. Liquid surface tension draws the material in the particle into a spherical shape. Other important particle shapes exist in the atmosphere e.g., asbestos is present as long fibers and fly ash can be irregular in shape. 

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