Double emulsion templates for efficient production of phase change microcapsules

Abstract

The utilization of phase change materials (PCMs) in thermal storage technology exhibits great potential for various applications in thermal management and latent heat storage systems. However, leakage of organic PCMs hinders its practical application. Encapsulation of PCMs in microcapsules with polymer shells can prevent PCM leakage while improving heat transfer and stability. In this study, shell monomers were introduced as an immiscible third phase into the traditional o/w two-phase emulsion system, and the formed three-phase complex emulsion was dynamically reconfigured to exhibit a core–shell encapsulated conformation induced by interfacial tension, resulting in the formation of a thermodynamically stable double emulsion. Microcapsules with 1,6-hexanediol diacrylate (HDDA) shells were successfully prepared using this double emulsion as a template. The emulsion configuration is of significant advantage in promoting stable encapsulation of the phase change material in the shell material, resulting in fast and efficient encapsulation and improved utilization of the phase change material. Phase change microcapsules with different phase change temperatures were prepared and characterized using n-octadecane (C18), methyl stearate (Mes), n-eicosane (C20) and n-docosane (C22) as phase change materials, respectively. Results show that the prepared microcapsules are spherically integrated, with smooth surfaces and obvious core–shell structures, and the enthalpies of phase transition of C18, Mes, C20 and C22 microcapsules are as high as 171.86, 122.37, 165.77 and 178.69 J/g, respectively. These microcapsules exhibit excellent thermal stability and durability and the encapsulation efficiencies exceed 99.7 % at different phase change temperatures. Furthermore, the potential applications of PCM microcapsules in the field of temperature regulation were also demonstrated. This double-emulsion template method provides a straightforward, rapid and scalable approach for the mass production of microcapsules with different core–shell compositions.