Abstract:

The foam properties of extended anionic surfactants with different structure were studied. The parameters such as foaming capacity （FC）, liquid-carrying capacity, foam expansion coefficient （FE）, drainage half-life, foam half-life, bubble number and foam polydispersity index （PDI） were obtained. The effects of introduction of propylene oxide （PO） units and ethylene oxide （EO） units in molecular structure on the foam properties were investigated. The results showed that, the slightly hydrophobic PO chain could not effectively bind water molecules, and the drainage of liquid film became faster, which reduced the stability of the foam. In contrast, the introduction of hydrophilic EO groups weakened the electrostatic repulsions between ionic headgroups, enhanced the ability of surface adsorption film to bind water molecules, reduced the drainage rate of the foam system, and thus improved the foaming performance. However, a too long EO chain would destroy the close arrangement of molecules in the surface film, which was unfavorable to surface tension reduction and thus led to worse foaming performance. The advantages in molecular structure of C₁₂E₃C enabled it to reduce the surface tension to 22 mN/m, indicative of the best foaming ability and foam stability. It could stabilize both big and small bubbles at the same time and form stable and lasting dry foams after 12 h. This work could provide reference to further explore the application of extended surfactants in foam systems.

Key words: extended surfactant, PO number, EO number, foaming capacity, foam stability