Dynamic Viscosity and Surface Tension Characterization of Paraffin-in-Water Nanoemulsions

This work studies the dynamic viscosity and surface tension of phase change material nanoemulsions (PCMEs) at dispersed phase concentrations of 2, 4 and 10 wt.%. Paraffin-in-water emulsions were produced by a solvent-assisted route, starting from RT21HC commercial paraffin with a nominal melting temperature of ~20-21ºC. In the case of the 4% mass concentration, a nanoemulsion containing 3.6% in RT21HC and 0.4% in a paraffin wax with a higher melting temperature (nucleating agent) was also analysed. Dynamic viscosity strongly increases with rising concentration of dispersed phase, enhancements in this property reach 150% for the sample with 10 wt.% loading at 5ºC. Nanoemulsions exhibit surface tensions considerably lower than those of water. However, PCME values are slightly higher than surface tensions measured for the corresponding water-SDS mixtures used to produce the nanoemulsions.