Microencapsulation of caprylic acid with different wall materials as phase change material for thermal energy storage

• Caprylic acid (octanoic acid) was microencapsulated with urea-formaldehyde resin, melamine-formaldehyde resin and urea+melamine-formaldehyde resin.
• Microcapsule with urea-formaldehyde resin has the highest latent heat.
• Microencapsulation emulsion temperature, stirring time and surfactant type were analyzed for determining the best microencapsulation process conditions.

In this study, caprylic acid (octanoic acid) suitable for thermal energy storage applications was microencapsulated with different wall materials, including urea-formaldehyde resin, melamine-formaldehyde resin, urea+melamine-formaldehyde resin. Microcapsules were prepared using coacervation method. Hardening process of microencapsulated phase change material (PCM) was done with formaldehyde. The morphology and particle sizes of microencapsulated PCM were analyzed by scanning electron microscopy, (SEM). The latent heat storage capacities of caprylic acid and microencapsulated caprylic acid were determined with differential scanning calorimetry (DSC). The chemical characterization of microcapsules was determined by Fourier transformed infrared (FTIR) spectroscopy. It is concluded that urea-formaldehyde resin was the best capsule wall material for caprylic acid. Based on all results, it can be considered that the microcapsules were synthesized successfully and that, the phase change enthalpies of melting and freezing were about 93.9 J/g and 106.1 J/g, respectively, the particle diameter was 200 nm–1.5 μm.