Abstract
Instead of relying on the usual, long-range shelf-test for determining emulsion stability, a technique utilizing the light scattering property of emulsions was developed to allow the determination within a short period of time.
In the previous report (Part 1), the oil phase was restricted to mineral oil and the concentration of the oil phase was kept constant in determining the effects of surfactant type and surfactant concentration on the stability index. It was found that the stable region was below stability index, R=0.33 and the unstable region was above R=0.46 Between these two R values, the stability was ambiguous.
In this report, four different oils, including a higher alcohol (hexadecyl alcohol), ester (isopropylmyristate), triglyceride (castor oil) and four different surfactants were studied at varying oil phase concentrations to determine the effects on stability indices.
The experimental data indicated that for isopropylmyristate, the stable region was below R=0.157 and the unstable region was above R=0.203. The stability was ambiguous between these two values. For hexadecyl alcohol, the stable region was below R=0.163 and the unstable region was above 0.211. For castor oil, the stable region was below R=0.177 and the unstable region was above 0.22. The values for the lanolin system were 0.209 and 0.251 respectively.
It is clear that the boundaries for the stable and unstable regions varied somewhat depending on the type of oils employed. The reason for the variation will be clarified in the future research work.
