RT Journal Article T1 Dynamic viscosity, surface tension and wetting behavior studies of paraffin-in-water nano-emulsions A1 Cabaleiro Álvarez, David A1 Hamze, Samah A1 Agresti, Filippo A1 Estellé, Patrice A1 Barison, Simona A1 Fedele, Laura A1 Bobbo, Sergio K1 2210.18 Física del Estado Líquido K1 2213 Termodinámica AB This work analyzes the dynamic viscosity, surface tension and wetting behavior of phase change material nano–emulsions (PCMEs) formulated at dispersed phase concentrations of 2, 4 and 10 wt.%. Paraffin–in–water samples were produced using a solvent–assisted route, starting from RT21HC technical grade paraffin with a nominal melting point at ~293–294 K. In order to evaluate the possible effect of paraffinic nucleating agents on those three properties, a nano–emulsion with 3.6% of RT21HC and 0.4% of RT55 (a paraffin wax with melting temperature at ~328 K) was also investigated. Dynamic viscosity strongly rose with increasing dispersed phase concentration, showing a maximum increase of 151% for the sample containing 10 wt.% of paraffin at 278 K. For that same nano–emulsion, a melting temperature of ~292.4 K and a recrystallization temperature of ~283.7 K (which agree with previous calorimetric results of that emulsion) were determined from rheological temperature sweeps. Nano–emulsions exhibited surface tensions considerably lower than those of water. Nevertheless, at some concentrations and temperatures, PCME values are slightly higher than surface tensions obtained for the corresponding water+SDS mixtures used to produce the nano–emulsions. This may be attributed to the fact that a portion of the surfactant is taking part of the interface between dispersed and continuous phase. Finally, although RT21HC–emulsions exhibited contact angles considerably inferior than those of distilled water, PCME sessile droplets did not rapidly spread as it happened for water+SDS with similar surfactant contents or for bulk–RT21HC. PB Energies SN 19961073 YR 2019 FD 2019-08-29 LK http://hdl.handle.net/11093/2166 UL http://hdl.handle.net/11093/2166 LA eng NO Energies, 12(17): 3334 (2019) NO Xunta de Galicia | Ref. ED481B-2017/017 DS Investigo RD 09-dic-2024