Fabrication of water-based composite phase change materials for cold energy storage with expanded graphite: Hydrophilic modification, particle size and mass fraction optimization

Mannitol water-based phase change materials have good prospects in the field of fruit and vegetable refrigeration and preservation. However, the unresolved trade-off between high latent heat and low thermal conductivity impedes the advancement of this technology. This paper fabricated the composite mannitol water-based phase change materials with expanded graphite as thermal conductive fillers modified by cetyltrimethylammonium chloride (CTAC). The antagonistic effect influenced by the non-polar nature and particle size of the expanded graphite was verified. The thermal properties of the composite materials were evaluated through differential scanning calorimetry, under different particle sizes of modified expanded graphite and proportions of modifiers, respectively. The optimum adsorption capacity was achieved with 80 mesh expanded graphite modified through 0.09 g CATC, which was increased by 74.13% compared to that of the unmodified expanded graphite. The contact angle decreased to 9.36° with the CTAC. The melting temperature of the composite material with a mass fraction of 9% MEG-80 was −2.43 °C, and the latent heat of melting is 277.19 J/g. Compared to mannitol water-based phase change materials, the maximum decrease in latent heat of melting was less than 10.31%. After 100 freeze-melt cycles, there was a small fluctuation in its melting temperature. The latent heat of melting only decreased by 3.72%. This study provides data support and reference for the feasibility of applying MEG/MW composite phase change materials in food refrigeration and preservation.