Rheology of systems containing cetomacrogol 1000—cetostearyl alcohol. II. Variation with temperature

Abstract

Gel networks in the continuous phases of emulsions of liquid paraffin in water stabilized by cetomacrogol 1000-cetostearyl alcohol mixed emulsifier have similar properties to those of ternary systems which form on dispersing the mixed emulsifier in water. The rheological changes with temperature of a typical emulsion and ternary system were examined by continuous shear (cone/plate viscometer) and creep (concentric cylinder viscometer) experiments. Variations in the viscosities and compliances were correlated with thermal-phase transitions determined microscopically. The nonionic network was tenuous. At high rates of shear, it fractured in the cone- and-plate gap, and further investigations were performed at lower shear rates. In creep, the extent of viscoelastic linearity was restricted, especially at high temperatures. The consistency of the ternary system increased to a maximum, as the temperature rose. The temperature of maximum consistency was close to the temperature at which the gel melted to form the liquid crystalline phase. At higher temperatures, the consistency decreased as the network weakened and finally dissolved to form isotropic solution. The emulsion plots did not reveal a temperature of maximum consistency. Abrupt changes in the compliance and viscosity plots vs temperature indicated that the emulsion network melted at a lower temperature than the ternary system. This was due to the liquid paraffin which lowered the temperature of phase transitions.