Preparation and properties of palmitic acid/SiO2 composites with flame retardant as thermal energy storage materials

Palmitic acid/silicon dioxide (SiO2) composites with flame retardant as thermal energy storage materials were prepared using sol–gel methods. In the composites, palmitic acid was used as the phase change material (PCM) for thermal energy storage, and SiO2 acted as the supporting material. In order to improve flame retardant property of the composites, melamine was added in the composites. Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD) and scanning electronic microscope (SEM) were used to determine chemical structure, crystalloid phase and microstructure of palmitic acid/SiO2 composites, respectively. The thermal properties, such as phase change temperature and latent heat, were investigated by a differential scanning calorimeter (DSC). Thermal stability was determined by a thermogravimetric analyzer (TGA). The SEM results showed that palmitic acid was well dispersed in the porous network of SiO2. The DSC results indicated that the composites solidify at 59.20 °C with a latent heat of 60.55 kJ/kg and melt at 59.76 °C with a latent heat of 85.11 kJ/kg when the mass percentage of palmitic acid in the composites was 41.1%. The TGA results showed that addition of melamine improved thermal stability. The microstructure of the charred residue after combustion indicated that the homogeneous and compact charred residue decreased the flammability of the composites.

Graphical AbstractThere are three-step thermal degradation processes. The weight loss of the TESM3 is relatively smaller than those of the TESM1 and TESM2 during three-step thermal degradation processes. The first step occurs at the temperature between 20 and 100 °C, corresponding to the release of water molecules adsorbed in the pores of the SiO2. The second step takes place from 180 to 240 °C, corresponding to the thermal degradation of the palmitic acid molecular chains. The third step happens from 350 to 550 °C, which may be assigned to the thermal oxidation process of the decomposed yields from the melamine.Figure optionsDownload as PowerPoint slideResearch highlights
► Palmitic acid/silicon dioxide (SiO2) composites with flame retardant as thermal energy storage materials were prepared using sol-gel methods.
► The melamine was added in the composites in order to improve flame retardant property of the composites.
► The composites solidify at 59.20 °C with a latent heat of 60.55 kJ/kg and melt at 59.76 °C with a latent heat of 85.11 kJ/kg when the mass percentage of the palmitic acid in the composites is 41.1%.
► The addition of the melamine can improve thermal stability. The homogeneous and compact charred residue may decrease the flammability of the composites.