Preparation and characteristics of microencapsulated stearic acid as composite thermal energy storage material in buildings

• Microencapsulated SA with SiO2 shell were prepared using sol–gel methods.
• Chemical structure and microstructure of the MPCM were determined by FT-IR and SEM.
• Thermal properties and stabilities were investigated by DSC and TGA.
• The SiO2 shells can improve the thermal stability of the microencapsulated SA.

Microencapsulated stearic acid (SA) with silicon dioxide (SiO2) shell as composite thermal energy storage material was prepared using sol–gel methods. In the composite thermal energy storage material, the stearic acid was used as the core material that is the latent heat storage phase change material (PCM), and the silicon dioxide acted as the shell material which prevented the leakage of the melted stearic acid. Fourier transformation infrared spectroscope (FT-IR) and scanning electronic microscope (SEM) were used to determine chemical structure and microstructure of microencapsulated stearic acid with silicon dioxide shell. The thermal properties and thermal stability were investigated by the differential scanning calorimeter (DSC) and thermogravimetric analyzer (TGA). The SEM results showed that the stearic acid was encapsulated in the shell of the silicon dioxide shell. The DSC results indicated that the microencapsulated stearic acid with the silicon dioxide shell as composite thermal energy storage material solidifies at 52.6 °C with a latent heat of 162.0 kJ/kg and melts at 53.5 °C with a latent heat of 171.0 kJ/kg when the encapsulation ratio of the SA is 90.7%. The TGA results presented that the silicon dioxide shells can improve the thermal stability of the microencapsulated stearic acid as composite thermal energy storage material.