Study of Wetting (I)

The Contact Angle of an Oil Droplet on Aqueous Solution of Nonionic Surfactant

Abstract

The wetting of an oily material on a nonionic surfactant solution have been studied in terms of the contact angle of an oil droplet on the nonionic surfactant solution, surface tension and the interfacial tension. Polyoxyethylene hexadecyl ether (C₁₆H₃₃-(0-CH₂CH₂) n-OH, n=5. 5-20) was used as a nonionic surfactant. Normal dodecane was used as a non-polar oily material. Oleic acid, oleyl alcohol, and corn oil were used as a polar oily material. The n-dodecane spread on the surfactant solution, in spite of the concentrations of surfactant like as duplex film. On the other hand, oleic acid, oleyl alcohol, and/or corn oil were dependent on the concentration of surfactant : in the case of a lower concentration of nonionic surfactant, although a large portion of the polar oily material formed a oil droplet in a state of lens, a part of it spread, and then penetrated into a surfactant layer at liquid-gas interface; in the case of a higher concentration of nonionic surfactant, the polar oily material formed the above-mentioned oil droplet without spreading onto the liquid-gas interface. This may be due to the fact that the state of adsorption of the nonionic surfactant molecule is dependent on the concentration and hydrophile-lipophile balance (HLB).