Surface rheological properties of a solid-state emulsion

A solid-state emulsion having good spreading properties shows two important transition ranges in the plot of storage modulus (G') as a function of shear strain when the state is changed from solid to liquid. However, a solid-state emulsion having lower spreading properties shows only one apparent transition range when the change from solid to liquid state takes place. The result implies the importance of surface properties in the solid-state emulsion. The first transition range is more important than the second transition range in order to understand the surface properties of a solid-state emulsion and is called the "surface transition range" in this article. The addition of water phase in the solid-state emulsion reduces the modulus in the surface transition range by increasing interfacial friction and weakening the matrix. The addition of pigments increases the modulus in the surface transition range by reinforcing the matrix, when there is no water phase in the solid-state emulsion. When the solid-state emulsion has water phase, however, the addition of pigments decreases the modulus in the surface transition range. The kinds and ratios of oils are also important factors to determine the properties of the matrix depending on their compatibility with wax.