High-performance palmityl palmitate phase change microcapsules for thermal energy storage and thermal regulation

Phase change microcapsules, which feature high latent heat and stability and can well mix with epoxy resin substrates, were synthesized through the solvent-free interfacial polymerization method with palmityl palmitate as the core material and low-toxicity dicyclohexylmethane 4,4′-diisocyanate as the shell material. The synthesized microcapsules were characterized by multiple techniques. The performances of microcapsules at different core-shell ratios were compared, and the applicabilities of epoxy resins with different contents of optimal microcapsules were investigated. Results show that, at a core-shell ratio of 16:4, the synthesized microcapsules achieve an encapsulation rate of 84.47%, and their enthalpies of melting and crystallization reach 218.49 J/g and 219.72 J/g, respectively. Moreover, the microcapsules exhibit outstanding thermal stability and reliability. They can remain intact without leakage after heating at 150 °C for 2 h, and their enthalpies of melting and crystallization can remain over 196.58 J/g and 202.23 J/g after 500 heating and cooling cycles. In addition, the microcapsules can uniformly disperse in epoxy resin, significantly influencing its heat transfer property and temperature regulation ability. With a 15% microcapsule content, the epoxy resin has a reduced thermal conductivity of 0.5834 W/mK, with delays of 76.0% and 51.4% in the time used for the temperature rise/fall process.