Influence of wax chemical structure on W/O emulsion rheology and stability

Abstract Waxy emulsions can show significant resistance to droplet coalescence. At temperatures below the appearance temperature of crystals, waxes precipitate, form a network and even can interact with the water/oil (W/O) interface favoring emulsion stability. In this sense, this work looks to provide a better understanding of wax chemical structure (macro - MA- and microcrystalline - MI) on water in oil (W/O) emulsion rheology and stability. Waxy emulsions were prepared with PE-b-PEG polymeric surfactant (0.5 wt. %) at different water fractions (10–50 wt. %) and cooling conditions (static and under shear). Waxes were characterized by 13 C NMR, DSC, and GC. The W/O emulsion properties were evaluated by rheology, thermal analysis, optical microscopy and laser light profiling. The results show that emulsions prepared with MA wax had higher elastic moduli; nevertheless, it showed a lower emulsion stability. Furthermore, emulsions containing MA wax exhibited a needle-shaped crystal while MI wax presents a rounder crystal (plate). Rheological studies show that the wax structure type and cooling conditions have important impacts on the elasticity and stability of W/O emulsions.