Dotchi Exerowa. Foams Stabilized by Hydrophobically-modified Inulin Polymeric Surfactant

Abstract

The foams and foam films stabilized by hydrophobically-modified inulin polymeric surfactant (INUTEC SP1) were investigated as a function of electrolyte concentrations. The Foam Pressure Drop Technique was applied to obtain the foam lifetime at constant capillary pressure. The Film Pressure Balance Technique was simultaneously applied to obtain the disjoining pressure as a function on film thickness. The results showed that at INUTEC SP1 concentration of 2 × 10 −5 mol.dm −3 and constant capillary pressure of 5 kPa the foam lifetime τ p was independent of electrolyte concentration in the range from 10 −4 to 10 −1 mol.dm −3 NaCl. Above 10 −1 mol.dm −3 NaCl, the foam lifetime increased rapidly with the increase in NaCl concentration and the most stable foams were produced from solutions containing 1 and 2 mol.dm −3 NaCl. The critical pressure P cr, foam above which foam collapse (avalanche-like) occurred increased with the increasing of electrolyte concentration and this explained the higher stability of the foam at high NaCl concentrations. The disjoining pressure (Π)-thickness (h) isotherms showed a different behaviour at low and high electrolyte concentrations. At 10 −3 mol.dm −3 NaCl, common thin films were obtained and the thickness decreased with increase in the pressure and rupture occurred at about 3 kPa. At 1 mol.dm −3 NaCl, black films were obtained with much smaller thickness that decreased slowly with the increase in Π and rupture occurred at about 2.7 kPa. These results indicated the transition from electrostatic to steric interaction as the electrolyte concentration was increased.

Synergy in Aqueous Systems Containing Bioactive Ingredients of Natural Origin: Saponin/Pectin Mixtures

“…The microinterferometric method of Scheludko–Exerowa [ 27 , 28 , 29 , 30 , 31 , 32 ] and the thin liquid-film–pressure balanced technique (TLF-PBT) [ 29 , 30 , 31 , 32 , 33 , 34 , 35 ] was applied for the investigation of the properties and stability of microscopic foam films. Film drainage evolution was studied using the Scheludko–Exerowa cell.…”