The Stability of O/W type emulsions as functions of temperature and the HLB of emulsifiers: The emulsification by PIT-method

Abstract

The properties of emulsions containing 3 wt% of polyoxyethylene nonylphenylether per system were studied as functions of temperature, composition, and the hydrophile-lipophile balance (HLB) of emulsifiers. It has been found that (a) the size of emulsion droplets changes remarkably with temperature and HLB of emulsifiers, (b) the diameter of droplets is very small but less stable towards coalescence close to the phase inversion temperature (PIT), (c) relatively stable O/W type emulsions are obtained when the PITs of respective systems are about 20°-65°C higher than the storage temperature, (d) a stable and fine emulsion is obtained by rapid cooling of an emulsion emulsified at the PIT, which process we shall designate "emulsification by the PIT-method," and (e) the optimum stability of an emulsion is relatively insensitive to the change of the HLB values or PITs of emulsifiers, but the instability of an emulsion is very sensitive to the PIT of the system. It seems difficult to determine the optimum HLB value of an emulsifier accurately from the stability vs. HLB value relation. On the other hand, since the change in the stability of an emulsion is sensitive to the temperature near the PIT, the selection of an emulsifier according to the PIT may be more accurate and reliable. © 1997 Elsevier Science Ltd. All rights reserved.