Preparation and Characteristics of Double-Shell Paraffin Microcapsules

Using paraffin as core material and the cheaper 2,4-diisocyanate (TDI), ethylene siamine (EDA), melamine and formaldehyde as shell materials, the double-shell microencapsulated phase change material (MicroPCM) for heat energy storage applications was synthesized by the interfacial and in situ polymerization. The synthesized microcapsules were characterized and analyzed by SEM and DCS; the mechanism of polymerization for the double-shell formation was studied, and the influences of emulsifying speed and stirring rate on the microencapsulation process were investigated too. The experiments show that the microcapsules prepared under the emulsifying speed of 9000 r·min-1 and the stirring rate of 300 r·min-1 have smooth morphologies with an average particle size of 4.0 μm; the latent heat of phase transformation of the prepared microcapsules reaches 180.5 J·g-1 and its temperature resistance is up to 200℃.It was found that the optimal molar ratio of EDA to TDI is 1:1.1~1:1.3, and the best molar ratio of melamine to formaldehyde is 1:1.5~1:1.8.