Portal de Periódicos da CAPES

Principles of Foam Formation and Stability

1989; Linguagem: Inglês

10.1007/978-1-4471-3807-5_1

1431-8539

P. Walstra,

Pickering emulsions and particle stabilization

A foam is commonly defined as a dispersion of gas bubbles in a liquid. In a "solid foam" the liquid has changed into a gel or a solid phase after making the dispersion. The volume fraction φ of gas in a foam is mostly between 0.5 and 0.97; if φ > about 0.75, the bubbles necessarily deform one another. Bubble size is mostly between 0.1 and 3 mm, which implies that the number ofbubbles is, say, 103 perml, as compared to, say, 1011 for emulsion droplets. The specific surface area of the bubbles is mostly a few times 100 cm2 per ml of continuous phase. The examples given below concern air bubbles in an aqueous phase; the surface tension of pure water is 73 mN m−2.