Preparation and Properties of Microencapsulated Phase Change Materials Containing Two-Phase Core Materials

Microencapsulated phase change materials (MicroPCMs) containing two-phase core materials, in which polypyrrole (PPy) particles were homodispersed in n-octadecane (n-Oct), were synthesized by two-step polymerization technique using poly(methyl methacrylate-co-allyl methacrylate) as shell. The surface morphologies, phase change properties, and thermal stabilities of the microcapsules were investigated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), respectively. The results show the two-phase core materials are well encapsulated in the presence of the emulsifier sodium salt of styrene-maleic anhydride copolymer. The average diameter of the microcapsules is about 35 mu m. The crystallization temperature of MicroPCMs is higher than that of MicroPCMs without PPy. At the same time, the enthalpy of the heterogeneous nucleation significantly increased with increasing of the PPy concentration. Microcapsules with 4-14 wt % PPy in the core material were free from obvious supercooling, and PPy had no influence on the morphology, the particle distribution, or the thermal resistant temperature of microcapsules.