Flexible phase change materials for thermal storage and temperature control

Flexible phase-change materials (PCMs) have great potential applicability in thermal energy storage and temperature control. A binary composite mixture comprising polyethylene glycols of solid and liquid phases (PEG2000 and PEG400, respectively) was synthesized as a PCM base material. The PEG400 liquid phase was uniformly dispersed in the PEG2000 phase-change crystal on a molecular scale, thus creating many micro- and nanocrystals of PEG2000 via polycrystalline growth from a single crystal. To retain solidity and flexibility in the composite's melted state, hydrogel technology and low-temperature drying were applied. We prepared flexible polymer gel shaped PCMs by adding sodium stearate (NaR) to the binary fused mixture. Needle-shaped NaR crystal grains of several hundred nanometers formed three-dimensional network structures, binding the binary flexible PCM within the network structure to form a polymer gel. These geometric structures not only achieve the solid-liquid PCM structure but also maintain flexibility in both the melted and solidified states (20-80 °C). The latent heats of melting and solidification for the polymer gel were 109.7 and 107.2 J/g, accounting for 87.5% and 85.8% of the PP20 binary eutectic, respectively. The demonstrated use of polymer gels provides a new route for investigating PCMs for heat storage.