Mechanical, thermal and microscopic properties of gypsum matrix composites containing capric acid-palmitic acid/urea-formaldehyde microcapsules

Fatty acids have great prospects for application in alleviating the energy crisis for buildings owing to their low corrosiveness, nonseparation of supercooled phases, and low costs. Capric acid–palmitic acid/urea-formaldehyde (CA–PA/UF) phase-change microcapsules were prepared using binary eutectic blends of CA and PA as the core materials and UF as the shell material. Subsequently, gypsum matrix composites were fabricated by mixing the prepared phase-change microcapsules in a gypsum matrix. The results show that the phase-change temperature and latent heat values of the binary eutectic fatty acid mixture in the optimal ratio of 0.85:0.15 were 26.7 °C and 189.7 J/g, respectively. The CA–PA/UF phase-change microcapsules were physically bound; that is, they were not chemically bound. Furthermore, the microcapsules did not react chemically with the gypsum matrix after incorporation and did not affect the crystal structures of the gypsum. The optimal content of the CA–PA/UF phase-change microcapsules was 10 wt%, at which the compressive strength, flexural strength, and thermal conductivity of the gypsum matrix composites were 4.90 MPa, 2.09 MPa, and 0.1854 W/(m·K), respectively.