Influence of acid and alkali reaction system on the morphology and thermal properties of paraffin@SiO2 phase change microcapsules for heat storage

Phase change materials are preferred in the field of thermal energy storage in low-medium temperature. Paraffin@SiO2 microcapsules were prepared by a sol–gel method at an acid and alkali reaction system. The field emission scanning electron microscope, Fourier transform infrared spectroscope, differential scanning calorimetry, and thermogravimetric analyzer were adopted to investigate the effect of the acid and alkali reaction system on the morphology, latent heat, and thermal stability of PA@SiO2 microcapsules. In the acid reaction system, the particle size and latent heat of PA@SiO2 microcapsules are in the range from 15 to 30 μm and from 132 to 174 J/g, respectively. However, comparing with the acid reaction system, there was a remarkable reduction in the particle size and latent heat of microcapsules prepared in the alkali reaction system. The initial weightlessness temperatures of PA@SiO2 microcapsules were 40 °C higher than that of paraffin, indicating that the SiO2 shell was beneficial to the microcapsule structure.