Preparation and characterisation of double-shelln-octadecane phase change material encapsulation

Double-shell MicroPCMs containing n-octadecane with ethylenediamine (EDA), 2,4-toluene diisocyanate (TDI), melamine and formaldehyde as shells, were fabricated by interfacial and in situ polymerisation technique. The influences of emulsifying rate and emulsifier sort on particle size distribution, structure and thermal stability of microcapsules have been systematically investigated. The morphology and structure of the microcapsules were examined by FT-IR, particle size, differential scanning calorimetry and SEM analyses, and the reaction principles of shell formations were analysed. The results show that the EDA reacted with TDI in a optimal molar ratio of 1:1.1–1.3, and the optimal molar ratio of melamine to formaldehyde was 1:1.5–1.8. The microcapsules are smooth morphologies, homogeneous size with an average pore size of about 2.0 μm, no aggregation on the condition of compound emulsifiers when emulsifying rate is 8000 rpm. The double-shell MicroPCMs display the highest thermal resistance temperature up to 250 °C and a high energy storage/release capacity of about 180 J g−1.