defoamers-tego-foamex.pdfVIP

TECHNICAL BACKGROUND / DEFOAMERS 44 Defoamers TEGO® Foamex TECHNICAL BACKGROUND / DEFOAMERS 45 It is almost impossible to imagine indus- try today without surfactants. Their use is required in the most diverse processes to obtain a broad range of effects. Emul- sifiers, for example, facilitate the incor- poration of water-insoluble binders in waterborne paints. Other examples in- clude additives which improve substrate wetting (see “Technical Background Sub- strate Wetting Additives“) and dispersion of pigments (see “Technical Background Wetting and Dispersing Additives“). Figure 1: Rise and bursting of air bubbles in a The most important property of these surfactant-free liquid surfactants is their tendency to concen- trate at interfaces such as the air/water boundary where they orientate accord- ing to their chemical structure. Surfactants have an amphiphilic molec- than that of the liquid, they rise. When In liquids containing surfactants, the ular structure. The hydrophilic area of the individual bubbles reach and pass unstable bubbles give rise to stable the molecule penetrates into the polar through a surfactant-free liquid, they foam consisting of spherical bubbles. A liquid and the hydrophobic part into the burst. Air from the bubbles dissipates surfactant film forms around the gas gas phase. Consequently, the surfactant