Лако-красочные материалы — производство

The terms defoamer and anti-foam are often used interchangeably, but they are not the same. A defoamer destroys an existing stabi­lized foam at the air interface. On the other hand, an anti-foam prevents the formation of a stable foam. However, it is difficult to distinguish between their mechanisms, and quite often, commer­cial products generally perform […]

The foam lamella is elastic in nature due to the Marangoni effect, which is a mass transfer phenomenon resulting from a surface-tension gradi­ent between two fluids. As the lamella is stretched, the concentration of the surfactant is reduced at the interface, producing a higher surface tension, which results in pulling the lamella back together by […]

Surfactants tend to concentrate in the lamella at a gas-liquid inter­face. With the drainage of the lamella, the inner and outer interfaces come closer together, and the electrostatic repulsion caused by the ionic groups of the surfactant prevents further drainage, so foam stabilization occurs.

Generally, pure liquids do not foam, but coatings, being multicom­ponent systems, may produce foam. When air is introduced into a liquid coating, bubbles are formed, which rise through the liquid to the surface. Upon reaching the surface, liquid from the bubble wall starts to drain under gravitational force and it becomes thinner. If the liquid […]

Foam is a gas, usually air, that has been dispersed and stabilized in a liquid. Air may get incorporated in coatings during manufacturing (such as by agitation) or during application (such as by spraying or brushing). Foam may also be produced when paint is applied on porous substrates such as wood or mineral surfaces as […]

Fluorosurfactants are anionic, cationic, or non-ionic surface-active materials having perfluorinated alkyl groups in their molecules. They strongly reduce surface tension and diminish the surface-tension gra­dient at the coating surface. They are more often used as anti-crater agents. The dosage of this type of flow additives should be just enough to achieve the desired effects, because […]

Unmodified low MW silicones (dimethylpolysiloxanes) are used as leveling and surface flow additives. Some modified silicones are also used as surface-flow control agents. Such chemical modifications may be either in the backbone of silicones, by replacing some of the methyl groups with alkyl or aryl groups, or via grafting on side chains, such as polyethylene […]

Cellulose acetobutyrate with high levels of butyric acid and medium MW is used as a leveling agent. It is typically used in wood coatings and automotive coatings. The low MW modifications are recommen­ded for unsaturated polyester resins and UV-curable varnishes. 1.3.1.2 Other polymers Some other polymers such as aromatic and aliphatic hydrocarbon resins, high MW […]

Polyacrylate leveling additives are homopolymers or copolymers of acrylates with alkyl, polyester or polyether modifications. They are normally supplied as solvent-free materials or as solutions. The per­formance of these additives is tailored through variations in their chemical composition (polarity and type of monomers) and MW, because their solubility and compatibility in coatings are dependent on […]

Polymeric leveling additives function through their tailor-made incompatibility in the paint film. During film formation, due to incompatibility, their molecules migrate to the interface. Unlike sili­cones, polymeric additives do not reduce the surface tension of the bulk of the paint film; rather, they reduce the local surface-tension gradient and thus create a physically uniform and […]