Preparation and characterization of gelatin-sodium alginate/paraffin phase change microcapsules

Paraffin is widely used in solar energy and building energy saving because of its high latent heat and low cost. However, it is easy to leak during the phase transition process, which has adverse effects on the thermal properties and thermal stability of paraffin. In this study, the composites of gelatin and sodium alginate were used as wall material, and the paraffin microcapsules were prepared by complex coacervation. The research studied the effects of the ratio of wall material, the core-wall ratio, the emulsification time, the volume of CaCl2 solution and the pH value on the thermal properties and thermal stability of microcapsules. And the characteristics of microcapsules were analyzed by Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD), laser particle size analyzer, scanning electron microscope (SEM), energy dispersive spectrometer (EDS), thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC), respectively. The results showed that the encapsulation ratio of microcapsules achieved 82.12 % when the ratio of wall material was 3:0.75, the core-wall ratio was 1.5:1, the emulsification time was 60 min, the volume of CaCl2 solution was 50 mL, and pH value was 4.5. Microencapsulation of paraffin improves the thermal stability and durability of paraffin. Microcapsules are spherical and the particle size distribution is affected by reaction conditions. The prepared microcapsules with suitable thermal properties and thermal stability, non-toxic and environmentally friendly can be applied to thermal energy storage system to improve energy utilization.