An Application of the Phase-inversion-temperature Method to the Emulsification of Cosmetics. I. Factors Affecting the Phase-inversion Temperature

Abstract

Recently, the PIT (phase-inversion-temperature) system was originated and developed by Shinoda and his collaborators as a guide to surfactant selection. In order to apply the PIT system to the cosmetic field, the effects of various factors on the PIT have been reinvestigated using cosmetic materials. POE alkyl ethers, whose distribution of EO chain lengths is broad, are widely used in cosmetics. In such a case, the effect of the distribution of the EO chain lengths is important. When a surfactant with a distribution of EO chain lengths was used, the PIT was lowered by an increase in the concentration of the surfactant, but when a monodisperse surfactant without any distribution was used, the PIT scarcely varied with the concentration of the surfactant. In the case of the surfactant with a distribution of EO chain lengths, however, if the ratio of oil to surfactant was kept constant, the PIT scarcely varied with the ratio of oil phase to water phase. This relationship can be used in estimating the PIT in the case of the practical production of an emulsion.

Microemulsions in Cosmetics and Detergents

“…In an early work with cosmetic ingredients the phase behaviour of potential base systems was investigated [49]. Different ethoxylated fatty alcohols were used in combination with paraffin and further cosmetic additives.…”

“…The addition of polar co-surfactants such as lauryl alcohol and oleic acid leads to a reduction of the PIT, while the addition of polar oils such as castor oil and octyldodecanol results in an increase of the PIT. These results can be summarised in a simple calculation scheme to estimate the PIT of compositions with cosmetic additives [50]. This approach was extended by many works, for example by Förster et al [51], who also used ethoxylated fatty alcohol with polar oils and co-emulsifiers.…”

Cloud point and phenol index of nonionic surfactants

“…Various methods for determining the effective HLB value in the presence of additives have been described elsewhere (38). They include measurements of cloud point (13^8,51,52), phenol index (31,32,(34)(35)(36)38), emulsion inversion point (29,30), and phase inversion temperature (1,11,14,33,40,43,50,51).…”