Paraffin-based nano-encapsulated PCM prepared from solvent-assisted emulsions in water

Phase Change Materials (PCM) like paraffin waxes have attracted much attention due to the possibility of exploiting their latent heat of fusion or solidification for the purpose of heat storage during heating or cooling, in addition to their chemical stability and tunable melting at moderate temperatures [1]. Anyway, due to some drawbacks as the low thermal conductivity and thermal hysteresis of PCM, the scientific community has been pushed to study more complex systems based on paraffin emulsions in water. Emulsions or nano-encapsulated PCM offer the advantage of higher heat transfer due to the presence of water phase and higher surface area of PCM phases. Applications include solar thermal storage [2], waste heat recovery, intelligent building, thermal regulating fabric, etc. [3]. The main problems related to these systems are the colloidal instability of emulsions that can lead to particles settling, creaming or flocculation, and the effect of supercooling that often arises for nano-sized PCM. In this work, nano-emulsions of paraffin waxes in water have been produced by a solvent-assisted route. Concentrations as high as 10 wt% have been obtained starting from two commercial paraffin waxes provided by Rubitherm GmbH, with nominal melting temperatures of 55 °C and 70 °C respectively.