Effects of temperature on water-in-oil emulsions stabilised solely by wax microparticles

The possibility of stabilising oil–water mixtures using wax particles alone is reported. As judged from contact angle measurements, wax particles are hydrophobic and act as effective emulsifiers of water-in-squalane emulsions. Specific differences exist depending on the chemical composition of the particles. The effect of temperature on emulsion stability has been explored in detail. If particles are pre-adsorbed to water drop interfaces by emulsification at room temperature, subsequent increase of temperature leads to a progressive increase in sedimentation and coalescence as particles melt and desorb from interfaces. The temperature range over which this occurs is similar to that of the melting range of the particles alone. If however the particles are melted prior to emulsification, surface-active long chain ester or acid molecules adsorb to freshly created interfaces giving rise to excellent stability to coalescence at high temperatures. Rapid cooling of these latter emulsions enhances their long-term stability as solidification of the molten wax leads to a thickening of the continuous oil phase.