High heat of fusion phase change materials (PCMs) are being intensively investigated for thermal energy storage/release for both defense and civilian applications. In PCMs, which can be broadly classified as inorganic (e.g. salt hydrates) or organic (e.g. paraffins), a relatively large amount of thermal energy is absorbed during melting and is then released during freezing. PCMs must be encapsulated for effective application and minimal amounts of encapsulant must be used for efficient application. In this work, PCM contents as high as 90% were achieved by encapsulating within polyHIPE (PH) monoliths produced by templating within high internal phase emulsions (HIPEs). The heat storage and release in the resulting PCM-containing monoliths was studied using thermal cycling. The advantages of salt hydrate PCMs include a sharp melting point, non-toxicity, non-flammability, and the availability of wide range of transition temperatures. Here, calcium chloride hexahydrate (CC-HH) was encapsulated within elastomeric acrylate-based polyHIPEs (Figure, left) that were produced by templating within water-in-oil Pickering HIPEs. The HIPE stabilization, the monomers, the crosslinking comonomer content, and the presence of a nucleating agent were used to modify the thermal behavior and the extent of leakage. The advantages of paraffin PCMs include minimal undercooling on freezing, congruent melting, self-nucleation, and low density. Here, octadecane (OD) was encapsulated within “green” polyHIPEs based on polyphenols such as tannic acid (TA) (Figure, right) that were produced by templating within oil-in-water HIPEs. The nature of the polyphenols and the presence of fillers were used to modify the thermal behavior, the extent of leakage, and the mechanical behavior.

Encapsulation of phase change materials within emulsion-templated polymer monoliths for thermal energy storage/release applications

256th National Meeting (2018)

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