Fabrication of microencapsulated phase change materials based on n-octadecane core and silica shell through interfacial polycondensation

In order to enhance the thermal transfer and phase change properties of microencapsulated phase change materials (micro-PCMs), a new micro-PCM based on n-octadecane core and silica shell was synthesized through interfacial polycondensation in different conditions. Fourier transform infrared spectra confirm the successful encapsulation of n-octadecane with inorganic silica. The silica microcapsules show a pronounced dependence of morphology and microstructure on the acidity of reaction solution in terms of the scanning electric microscopy observation, although all of them exhibit a well-defined core–shell structure. It is found that the microcapsules formed at pH 2.89 achieve a compact silica shell with fairly smooth surface as well as a large mean particle size of about 17.0 μm. Wide-angle X-ray scattering patterns indicate that the crystalline nature of the microencapsulated n-octadecane is maintained despite the confinement of silica shell. Thermogravimetric analysis shows that the silica microcapsules perform a typical two-step degradation process and present a good thermal stability. Differential scanning calorimetry investigation indicates that the silica-microencapsulated n-octadecane can achieve good phase change properties and high encapsulation efficiency by controlling the acidity of the reaction solution as well as the loading content of core material in synthesis. The thermal conductivity of the silica microcapsules is also significantly improved due to the presence of high thermal conductive silica shell. Encapsulation of n-octadecane with the silica shell material through interfacial polycondensation can be a perspective way to prepare the micro-PCMs with enhanced thermal transfer and phase change properties for potential applications to thermal-regulating textiles and fibers.