Preparation and characterization of flame-retardant nanoencapsulated phase change materials with poly(methylmethacrylate) shells for thermal energy storage

In this work, flame-retardant nanoencapsulated phase change materials (NanoPCMs) containing n-octadecane as the core material and poly(methylmethacrylate) (PMMA) as the shell material were successfully fabricated by introducing diethyl bis(2-hydroxyethyl acrylate)amino methylphosphonate (DEAMP) as the crosslinking agent via miniemulsion polymerization. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analyses confirmed that n-octadecane was successfully encapsulated into the PMMA shell and that the NanoPCMs exhibited a regular spherical profile. The phase change properties, thermal reliability, thermal stability, and flame-retardant properties of NanoPCMs were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), cone calorimeter tests, and limiting oxygen index (LOI) measurements. The DSC results showed that the NanoPCMs possessed a relatively high encapsulation efficiency in the range of 86.5-94.0% for n-octadecane. The thermal properties and durability of the NanoPCMs were almost unchanged after the introduction of DEAMP into the NanoPCMs. The combustion test results showed that the introduction of phosphorus-based flame retardant DEAMP into the NanoPCMs significantly suppressed the heat and smoke releases and, increased the residual weight and LOI value of the EP/NanoPCM composites. In addition, a computer-aided thermal measurement system was created to investigate the thermoregulation properties of the NanoPCMs and the results showed that the addition of NanoPCMs into a gypsum board significantly improved the thermoregulation properties. In conclusion, the flame-retardant NanoPCMs showed considerable potential for thermal energy storage applications, especially in thermoregulated textile and construction fields.