Association and solubility studies of mixed polyglycol ether surfactants in water
Bassem M. Bajouk, Rolf O. Sköld
Department of Applied Surface Chemistry, Chalmers University of Technology, Kemivägen 10, SE-412 96 Göteborg,Sweden
The effect of varying the molecular structure and the type of counter ion of polyglycol ether based anionic
surfaceactive components on the processes of phase separation, adsorption to the air-water interface and
molecular association in aqueous model metalworking formulations containing a polypropylene glycol was
studied. Phase separation and micellization were studied via static surface tension measurements and by
using an instrument, which enables the automatic scanning of temperature and concentration dependent pH,
turbidity and conductivity data. The anionic surfactants investigated were highly water-soluble and the
surface tension isotherms of all formulations were found to display a common anomalous trend characterized
by an initial maximum in the Gibbs surface excess function followed by a plateau region before a second
maximum occurs just before the concentration taken to indicate micellization. The aqueous mixtures in most
cases displayed concurrent phase separation and micelle formation, which has to be taken into account when
comparing critical micelle concentrations (CMCs). The present availability of parallel data, turbidity data in
particular, allowed incipient phase separation to be detected. This is a circumstance, which would otherwise
pass unnoticed, since it is not visually detectable. Results are considered industrially useful since the control
of the isotropic temperature - concentration space is a key aspect in the design and fine-tuning of
environmentally benevolent aqueous functional fluids for specific applications.
© 2002 Elsevier Science B.V. All rights reserved.
Colloids and Surfaces A: Physicochem. Eng. Aspects 212 (2003) 65 -/77
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