Synthesis and Characterization of Hydrophobic Phase Change Microcapsules With <scp> SiO ₂ </scp> / <scp>PUA</scp> Composite Shell

ABSTRACT In order to expand the application of phase change microcapsules in energy storage systems and functional coatings, PCMs with n‐tridecane as the core and a silica/polyurea composite shell were prepared via an interfacial polymerization‐sol–gel method. FT‐IR and EDS analyses confirmed the successful encapsulation of n‐tridecane and the integrity of the composite shell structure. SEM observations showed that the microcapsules possessed a regular spherical morphology with a uniform particle size distribution of 500–1000 nm and an average diameter of 623.6 ± 12.8 nm, which is favorable for their homogeneous dispersion in coatings and composite matrices. DSC results revealed two characteristic phase transition peaks of n‐tridecane, and a high latent heat of 100.21 ± 2.7 J/g was achieved at a core‐to‐shell mass ratio of 5:2. TGA demonstrated that the silica/polyurea shell significantly enhanced the thermal stability of the microcapsules. After 150 thermal cycles, the latent heat retention exceeded 96%, indicating excellent cycling reliability and effective leakage prevention. Moreover, the microcapsules exhibited good hydrophobicity with a contact angle of 133.52° ± 1.6°. Overall, the microcapsules exhibited a favorable combination of high thermal storage capacity, excellent thermal stability, and hydrophobic surface properties, demonstrating strong potential for energy storage and hydrophobic functional coating applications.