Preparation and characterization of reusable water/ethylcellulose phase change cold storage microcapsules with high latent heat

To improve the applicability of water-based cold storage materials in short-distance cold chain transport, low-temperature phase change microcapsules with water core and ethylcellulose (EC) wall were prepared by double-emulsion solvent diffusion. Core–shell microspheres with an average particle size of 1.6 µm were obtained under process parameters optimized using the response surface methodology. The presence of hydrogen bonds between water and EC was confirmed by Fourier transform infrared spectroscopy. The results of differential scanning calorimetry and thermal conductivity show that the microcapsules exhibited superior thermal storage (286.51 J/g) and the thermal conductivity is 0.4655 W/m·K. On the basis of the temperature-time curve, the time that the microcapsules were kept within the cold storage temperature range (0–7 °C) was 13.3 times that for water, and the refrigeration capacity of the microcapsules was significantly improved. After 100 freeze–thaw cycles, the supercooling degree of the microcapsules remained 0.7 °C lower than that of water without phase separation. Additionally, thermogravimetric analysis and leakage testing were used to characterize the thermal stability and reusability. Furthermore, the simulation of application conditions shows that the refrigeration time of the combined thermal insulation materials and microcapsules could reach 137 min, which was 63.1% longer than that of the control group. All the results suggest that water/EC microcapsules show potential as cold thermal energy storage material that can be reused in short-distance cold chain transport.