Matthias Hloucha

Polymer-Stabilized Emulsions: Influence of Emulsion Components on Rheological Properties and Droplet Size

We investigated o/w-emulsions containing polymeric thickener C10–C30 acrylate (acrylate) and silicone-based emulsifier PEG-12 dimethicone (PEG-12) but without low molecular mass surfactants. Mechanical properties of emulsions were probed by oscillatory and continuous flow rheometry while droplet size was studied by flow particle image analysis (FPIA). By varying thickener and emulsifier content rheological properties and droplet size of emulsions changed significantly. Experimental results and a statistical analysis showed that the physical network, built up by acrylate in a concentration range from 0.1–%[wt.]1.0, was the dominating factor for rheological properties and increased moduli and viscosity of emulsions. The development of droplet diameters revealed that a systematic control of droplet parameters was possible by increasing the PEG-12 concentration from 0.0–%[wt.]5.0. In contrast, increasing acrylate concentration led to either large or small droplets. The influence of larger droplets in the emulsions was revealed when the arithmetic diameter and the Sauter diameter were compared and displayed huge differences. These differences resulted from a rather small amount of big droplets with diameters above 40 μm. An influence of oil droplets on emulsion elasticity was only observed for emulsions with low acrylate concentration (≤ 0.1 wt. %), because at higher concentrations the influence of oil droplets was superimposed by thickening properties of acrylate.