Nucleation of PCMs in confined geometries.

This work investigates the influence of particle size on crystallization behaviour of microencapsulated and emulsified n-octadecane using differential scanning calorimetry (DSC) and laser diffraction. Analyses of microcapsules show a stepwise decrease of nucleation temperature (from 26 °C to 14 °C) with decreasing particle size (from 300 μm to 3 μm). Further reduction of particle size in emulsions (< 0.2 μm) results in a slight decrease of nucleation temperature (<2 K). Analyses of cooling thermograms of emulsions show two peaks, a minor peak around 8-9 °C and a major peak, which onset nucleation temperature Tc is influenced substantially by the lipophilic character of the surfactants (Tc varies between 13 °C and 22 °C).
The minor peak is attributed to the transition from rotator to stable crystal phase and its signal increases with decreasing particle size.