Preparation and Characterization of Form-stable Phase Change Materials with Hydrogel Skeleton as Supporting Material

Form-stable phase change materials (FSPCMs) are a kind of latent heat/cold energy storage materials and play key role in fields like new energy development, cold chain temperature control and healthcare. Lots of expensive chemicals have been investigated as phase change materials (PCMs) for FSPCMs, however, the application of water, a very cheap and abondance material in our planet, as a phase change cold energy storage material for FSPCMs is neglected. Herein, a kind of hydrogel based on poly(vinyl alcohol) and poly(acrylic acid) was prepared at first, and then novel FSPCMs with high latent cold energy storage capacity were obtained by solving the problem of water leakage in the hydrogel through simple surface freeze drying. The latent cold energy storage capacity of the obtained hydrogel-based FSPCMs attained 237 J/g, and the water in the FSPCMs would not volatilize when the temperature was not higher than 50 degree celsius. The FSPCMs also exhibited excellent anti-leakage performance even it was heavily pressed. Meanwhile, the FSPCMs possessed good long-term thermal reliability and its latent cold storage performance has not changed after 50 freeze-thaw cycles. The FSPCMs also had good temperature control and shaping properties, making it applicable to cold storage, cold chain temperature control, cold compress and other fields. In addition, in order to fully utilize the high porosity of dried hydrogel, exfoliated graphite nanoplatelets (xGnP) were applied to enhance the stability of the hydrogel skeleton with the largest water content, and a novel supporting material with high porosity was obtained by freeze-drying. Then, erythritol (ET) and PEG2000, two water-soluble PCMs, were selected as representatives, and two types of FSPCMs were prepared by melting impregnation. Both types of FSPCMs possessed very high content of PCMs and very high latent heat storage capacity, which proved that polymer network skeletons of hydrogels were perfect supporting materials for FSPCMs. Consequently, the results obtained in this study have important value for promoting the application of hydrogel itself and hydrogel materials in the fields of heat energy storage and temperature control.