Preparation and Performance Study of Titanium Dioxide-Urea-Formaldehyde Resin Composite Shell Phase Change Microcapsules for Cold Storage

TiO₂-UF@ Tet microcapsules were prepared using a two-step method in which the advantages of organic and inorganic shell layers were combined. The effect of the mass fraction of TiO₂ on the performance of the composite-shell phase-change microcapsules was investigated. The morphology, chemical composition, and thermodynamic properties of the phase change microcapsules were investigated using biological microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, energy-dispersive spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The experimental results showed that the microcapsules formed by TiO₂ and UF using the two-step method had a good composite shell structure. The phase-transition temperature of the microcapsules decreased, the latent heat of the phase transition decreased, and the thermal conductivity increased continuously with an increase in the mass fraction of TiO₂. The prepared microcapsules had smooth surfaces, a uniform particle size distribution, and an average particle size of approximately 2.0 μm. The phase transition temperature and latent heat of the optimal composition were 3.1 ℃ and 168.5 J/g, respectively, with a coating rate and coating efficiency of 71.64% and 69.08%, respectively. After 100 heating cycles, the phase-transition temperature remained stable and the microstructure was good. These microcapsules are suitable for cold-storage air conditioning systems.