Microencapsulation of n-eicosane as energy storage material synthesized by interfacial polymerization

For heat energy storage application, polyurea microcapsules containing phase change material, n-eicosane, were synthesized by interfacial polymerization method with toluene -2,4-diisocyanate (TDI) and ethylene diamine (EDA) as monomers in an emulsion system. Poly (ethylene glycol) octyl-phenyl ether (OP), a nonionic surfactant, was the emulsifier for the system. The experiments indicated that TDI was reacted with EDA in a mass ratio of 1.9 to 1. The sizes of microcapsules were analyzed with TEM and laser particle analyzer, which showed the empty microcapsules were about 0.2 mu m and those containing n-eicosane were 2-6 mu m. FTIR spectra proved the formation of wall material, polyurea, from the two monomers, TDI and EDA. Encapsulation efficiency of n-eicosane was about 75%. Microcapsules of n-eicosane melted at a temperature close to that of n-eicosane, while its stored heat energy varied with the amount of core material n-eicosane. Thermogravimetric analysis revealed that the core material n-eicosane, micro-n-eicosane, and wall material polyurea could withstand temperatures up to 130 degrees C, 170 degrees C, and 270 degrees C, respectively.