Contact angle of surfactant solutions on precipitated surfactant surfaces. II. Effects of surfactant structure,presence of a subsaturated surfactant,pH, and counterion/surfactant ratio |
| |
Authors: | Piyada Balasuwatthi Nimit Dechabumphen Chintana Saiwan John F Scamehorn |
| |
Affiliation: | (1) Petroleum and Petrochemical College, Chulalongkorn University, 10330 Bangkok, Thailand;(2) Institute for Applied Surfactant Research, University of Oklahoma, 73019 Norman, Oklahoma;(3) University of Oklahoma, 100 East Boyd, School of Chemical Engineering and Materials Science, 73019 Norman, Oklahoma |
| |
Abstract: | The contact angle of a saturated aqueous surfactant solution on the precipitate of that surfactant was measured by using the
sessile drop method. The sodium and calcium salts of alkyl sulfates (C12, C14, and C18) had advancing contact angles higher than those of alkyl trimethylammonium bromides (C14, C16, and C18). The measured advancing contact angles for several surfactant solutions did not substantially change with varying surfactant/counterion
ratios; therefore, the precipitating counterion concentration (e.g., water hardness) had little effect on the wettability.
The contact angles of fatty acid (C12 and C16) solutions did not show any dependence on pH between a pH of 4 and 10. The contact angles of saturated calcium dodecanoate
(CaC12) solutions containing a second subsaturated surfactant (sodium dodecyl sulfate: NaDS) decreased with increasing NaDS concentrations
until reaching the critical micelle concentration of the surfactant mixture. These results show that the second suractant
can act as a wetting agent in this saturated surfactant system. Application of Young’s equation to contact angles showed that
the solid/liquid surface tension can change substantially with surfactant concentration and be important in addition to the
liquid/vapor surface tension in reducing contact angles. Application of the Zisman equation results in a “critical” surface
tension for the CaC12 or soap scum of 25.5 mN/m, which is comparable to difluoroethene. |
| |
Keywords: | Contact angle defoamer hydrophobicity wetting |
本文献已被 SpringerLink 等数据库收录! |
|