Near-Contact Motion of Surfactant-Covered Spherical Drops: Ionic Surfactant.
J Colloid Interface Sci
; 211(2): 355-366, 1999 Mar 15.
Article
en En
| MEDLINE
| ID: mdl-10049551
A lubrication analysis is presented for near-contact axisymmetric motion of spherical drops covered with an insoluble nondiffusing surfactant. The surfactant equation of state is arbitrary; detailed results are presented for ionic surfactants. The qualitative behavior of the system is determined by the dimensionless force parameter &Fcirc;, the external force normalized by the maximum resistance force generated by Marangoni stresses. For &Fcirc; > 1 drops coalesce on a time scale commensurate with the coalescence time tau0 for drops with clean interfaces. For &Fcirc; < 1, the system evolves on the time scale tau0 until Marangoni stresses approximately balance the external force; thereafter a slow evolution occurs on the Stokes time scale. In the long-time regime a self-similar surfactant concentration profile is attained that scales with the extent of the near-contact region. The gap width decreases exponentially with time but slower than for rigid particles because of surfactant backflow. For &Fcirc; < 1, drop coalescence does not occur without van der Waals attraction. Quantitative results depend only moderately on the surfactant equation of state. Copyright 1999 Academic Press.
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Colección:
01-internacional
Base de datos:
MEDLINE
Tipo de estudio:
Qualitative_research
Idioma:
En
Revista:
J Colloid Interface Sci
Año:
1999
Tipo del documento:
Article
Pais de publicación:
Estados Unidos