The Effect of Surfactants on Equilibrium Wetting

• Published in: Croatica Chemica Acta Vol. 52; no. 2; p. 139
• Main Authors: Summ, B. D., Goryunov, Yu. V., Markina, Z. N.
• Format: Conference Proceeding
• Language: English
• Published: Hrvatsko kemijsko društvo 25.06.1979
• ISSN: 0011-1643; 1334-417X

Contact angles B0 of aqueous solutions contacting with hydrophilic and hydrophobic surfaces were studied as affected by various surfactants (alcohols, fatty acids, soaps) under conditions close to thermodynamic equilibrium (in the atmosphere saturated with the solution vapour). The conditions of transitions from limited wetting (Bo > 0) to complete wetting, i.e. spontaneous spreading were also studied. The effect of surfactants adsorption at the solid gas interface was estimated from the isotherms of wetting tension W = cr1g Cos B0 (cr1g is the surface tension of the solution) on the basis of equation describing W as a function of concentration. It is shown that adsorption of surfactants at the solid-gas interface markedly affects wetting of hydrophilic materials. For hydrophobic materials the effect is primarily due to adsorption of surfactants at the solid- solution and solution-gas interfaces. It was found that equilibrium wetting is affected by the type of adsorption at the solid surface (physical or chemical adsorption). The influence of hydrocarbon chain length in homological series of alcohols and fatty acids on equilibrium contact angles and on transition to spontaneous spreading was studied as well.