Development of highly stable paraffin wax/water phase change material nano-emulsions as potential coolants for thermal management

This study was to explore the hydrophilic surfactant/Brij L4 mixture scheme for fabrication of highly stable paraffinic nano-emulsions melting at 55 degrees C by the low-energy phase inversion temperature method that has not been reported previously. Two commercial paraffin waxes were chosen as the PCM agents, Sasolwax 5203 with a higher onset Tm of 54 degrees C in the initial development and OP44E with a lower onset Tm of 44 degrees C for further assessment and fabrication. At accelerated stability testing by thermal approach, the rate of droplet size increase was mainly attributed to Ostwald ripening destabilization mechanism, and decreased by about 5 times for every 5 degrees C drop. Only a moderate increase in the particle size was observed, from 47.7 nm to 120.6 nm, over a period of 9 months at 45 degrees C. The exciting results in the accelerated stability evaluation greatly outperformed than those previous results only obtained from the regular stability testing including room temperature storage and heating-cooling cycles in a container, and hence this experimental result can offer a more meaningful reference in terms of service life of nano-emulsions flowing in pipelines. With the optimized surfactant mixtures, a series of highly stable paraffinic nano-emulsions in the working temperature range of 30-50 degrees C were successfully formulated as promising coolants in the active thermal management system.