Flame-retardancy and thermal properties of a novel phosphorus-modified PCM for thermal energy storage

Organic phase change materials are flammable, which limits their applications in heat storage and conversion. In the presented study, a phosphorus-grafted hexadecanol was blended with pentaerythritol phosphate (PEPA) to prepare flame-retardant phase change material (FRPCM). The thermal properties of FRPCM were evaluated by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and cone calorimetry. The flame-retardant mechanism was examined by thermogravimetric analysis-Fourier transform infrared spectrometry (TG-FTIR) and scanning electron microscopy (SEM) tests. The FRPCM maintains a promising heat storage capacity (186.9 J/g) and thermal stability after grafting and blending. The flame retardance analysis reveals that the grafted phosphorus group helps to promote char formation. PEPA extends the time before exposed combustible material ignites. The cone calorimeter test demonstrated that the peak heat release rate and total heat release are further decreased by more than 50%, owing to the synergistic effect between the phosphorus group and PEPA. The SEM results showed that a porous structure is formed during combustion. Self-extinguishment testing indicates that the FRPCM is extinguished in a much shorter time than is hexadecanol.