The foaming behavior of nonionic alkyl glucosides, in terms of foamabi
lity 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 s
olutions made from either a linear octyl beta-glucoside, a linear octy
l alpha-glucoside, or a branched octyl alpha-glucoside, 2-ethylhexyl a
lpha-glucoside. At low surfactant concentration there is only a small
difference in foamability between the surfactants, which remains when
the salt concentration increases. At all surfactant concentrations tes
ted octyl beta-glucoside is observed to be the best foaming agent. The
stability of the individual foam lamellae has also been studied with
the thin-film-balance (TFB) technique. The stabilizing forces in these
nonionic foam films are, in most cases, electrostatic double-layer fo
rces. The thickness dependence of the repulsive forces is consistent w
ith Poisson-Boltzmann theory. As the salt concentration is increased,
the range of the double-layer force observed below the cmc decreases,
as expected. This trend correlates with a reduction in foam stability
whereas the foamability is only marginally affected by the salt concen
tration. For the octyl beta-glucoside close to the cmc, only a very we
ak double-layer force is observed, but for this surfactant Newton blac
k films stabilized by steric/hydration forces are formed.