Abstract
The effects of lipophilic surfactants with various short ethylene oxide (EO) chain lengths on Cloud Point (CP) and Phase Inversion Temperature (PIT) have peen studied by using homogeneous polyethyleneglycol dodecylethers. The CP of hydrophilic surfactant aqueous solution decreased when lipophilic surfactant was added. The degree of reduction in CP was correlated with Inorganic Organic Balance (IOB) value of the lipophilic surfactant. The PIT of the n-decane-water-nonionic surfactant system also decreased as lipophilic surfactant added. The degree of reduction in PIT was in reverse relation to that of reduction in CP against the IOB value of lipophilic surfactant. These phenomena could be explained by investigating each partition of lipophilic and hydrophilic surfactants contained in the three phases i.e. oil, water and surfactant phases, which appear at PIT.
It was found that the most of nonionic surfactants were distributed to the oil and the surfactant phases. The cantent of lipophilic surfactants in the oil phase decreased and that in the surfactant phase increased, as the EO chain lengths of lipophilic surfactants increased.
It was also found that, when PIT was fixed at 70°C, the average EO chain length of nonionic surfactant existing in the surfactant phase was held almost constant at around 7 under different combinations of nonionic surfactants.
