Composite macrocapsule of phase change materials/expanded graphite for thermal energy storage

Three kinds of macro-encapsulated phase change materials (MacroPCMs) were fabricated, i.e., MacroPCMs with a single core–shell structure, MacroPCMs containing microencapsulated phase change materials (MicroPCMs), and composite macrocapsules of MicroPCMs/expanded graphite prepared by suspension-like polymerization followed by a piercing–solidifying incuber process. The morphology, microstructure, phase change property, as well as seal tightness were systematically characterized by field emission scanning electron microscope (FESEM), differential scanning calorimetry (DSC), and energy dispersive X-ray spectrometer (EDS). The core–shell structured macrocapsules exhibit a homogeneous thickness shell. The interface combination between MicroPCMs and polymer substrate was studied through the cross section micrograph of MacroPCMs containing MicroPCMs. The morphology and seal tightness of MacroPCMs fabricated with expanded graphite absorbing both PCMs and shell-forming monomers, enhanced significantly compared with that of PCMs alone. In addition, the effects of polymer substrate proportion between styrene-maleic anhydride copolymer and sodium alginate on the microstructure and performance of MacroPCMs were discussed as well.