Fabrication and Characterization of Flame-Retardant Nanoencapsulated n-Octadecane with Melamine–Formaldehyde Shell for Thermal Energy Storage

An innovative reactive phosphorus–nitrogen containing diamine, PNDA, was obtained by dehydration reaction between 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and 4,4′-diaminobenzophenone (DABP). Then, flame-retardant nanoencapsulated n-octadecane (NanoC18) with PNDA-modified melamine–formaldehyde (MF) as shell was fabricated via in situ polymerization. n-Octadecane was successfully encapsulated in the PNDA-modified MF polymer shell and the diameter of NanoC18 ranged within 80–140 nm, as evidenced by scanning electronic microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The thermal property and flame retardancy of NanoC18 were researched by thermogravimetric (TGA), differential scanning calorimetry (DSC), cone calorimetry measurement, and limiting oxygen index (LOI) test. DSC analysis indicated that NanoC18 exhibited a relatively high phase change enthalpy within the range of 110.8–141.3 J/g. The results of the combustion test indicated that the introduction of the phosphorus–nitrogen containing PNDA into NanoC18 considerably increased the LOI and residual weight of EP/NanoC18 composites, as well as suppressed the release of heat and smoke. Moreover, the thermal properties, thermal stability, and durability of NanoC18 were barely changed upon PNDA introduction into NanoC18. This nanoencapsulated n-octadecane with an excellent phase change properties and flame-retardant properties exhibits considerable potential for energy saving construction, thermoregulated textile and other thermal energy storage applications.