S. Verma et Vv. Kumar, RELATIONSHIP BETWEEN OIL-WATER INTERFACIAL-TENSION AND OILY SOIL REMOVAL IN MIXED SURFACTANT SYSTEMS, Journal of colloid and interface science (Print), 207(1), 1998, pp. 1-10
Detergency of oily soil is a complex kinetic process that includes con
tributions from the wash system physical properties, time and temperat
ure of wash, and the hydrodynamic forces exerted during the wash proce
ss. Generally, surfactant mixtures that exhibit a low oil-water interf
acial tension are considered to provide superior oily soil detergency.
In our investigations, we measured the oil-water interfacial tension
for C12EO3/NaLAS and C12EO7/NaLAS blends as a function of temperature
(18-80 degrees C) and time (0-60 min). The oil-water interfacial tensi
on was found to decrease as a function of time for all blends containi
ng nonionic surfactants, and this decline was most rapid for blends co
ntaining a higher fraction of ethoxylated alcohol with less than 3 mol
of ethylene oxide. It is proposed that the diffusion of this hydropho
bic fraction into the oil phase leads to the measured decline in the o
il-water interfacial tension. Also, due to this limitation, no general
correlation of oil-water interfacial tension with oily soil removal w
as observed. In view of these observations, it appears that the measur
ement of the oil-water interfacial tension (using a spinning drop tens
iometer) for solutions containing hydrophobic surfactants may give mis
leading-results. (C) 1998 Academic Press.