The Solid–Liquid Phase Diagram of Binary Mixtures Dissolved in an Inert Oil: Application to Ternary Blends that Can Form Organogels

Abstract

AbstractA simple generalization of the Hildebrand equation is presented for the prediction of the solid–liquid phase diagram of a binary mixture of structuring agents dissolved in an inert liquid. The model is a thermodynamic interpolation between three well‐known limits: (1) the freezing depression curve of liquid A under influence of the addition of the solvent, (2) the freezing depression curve of liquid B under influence of the addition of the solvent, and (3) the binary solid–liquid phase diagram of substances A and B. The theory is shown to be valid as long as the freezing temperature of the liquid is well below the freezing temperatures of the structurants. The theory is compared to literature data for three different mixtures: (1) stearyl alcohol and stearic acid dissolved in sunflower oil, (2) hentriacontane+melissic acid in safflower oil, and (3) lauric acid + behenic acid in canola oil. The agreement between the thermodynamic calculation and experimental data is good. The solid–liquid phase behavior of glyceryl tristearate + stearic acid in edible oil is also studied. The location of the eutectic point of the latter system is predicted to shift toward an axis with zero tristearate concentration as the structurant concentration decreases from 50% to 5% (w/w).