Foam and thin-liquid-film studies of alkyl glucoside systems

• The foaming behaviour of nonionic alkyl glucosides, in terms of foamability and foam stability, has been investigated using various methods. Three different foam tests, two dynamic methods: the Bikerman cylinder and the Watkins funnel, and one static method, have been employed for measuring the foamability and foam stability of nonionic surfactant solutions made from either the linear octyl b-glucoside, the linear octyl a-glucoside, or the branched octyl a-glucoside, 2-ethylhexyl a-glucoside. At low surfactant concentration there is only a small difference between the surfactants, which remains when the salt concentration increases. At high surfactant concentration octyl b-glucoside is observed to be the major foaming agent. The stability of the individual foam lamellae have also been studied with the Thin-Film-Balance technique (TFB). The stabilizing forces in these nonionic foam films is, in most cases, electrostatic double-layer forces. The thickness dependence of the repulsive forces is consistent with Poisson Boltzmann theory. As the salt concentration is increased the range of the double-layer force measured with the TFB technique decreases. This correlates with a reduction in foam stability as noticed by measuring the decay of foams formed by a shaking method. Furthermore, for the octyl b-glucoside close to cmc, only a very weak double-layer force is observed, and in this case Newton black films stabilized by steric/hydration forces are formed as noticed by TFB measurements.

Nyckelord

Foamability

foam stability

thin-liquid-films

alkyl glucosides

Thin-Film-Balance

double-layer forces

Newton black film

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ref (ämneskategori)

art (ämneskategori)