Effect of Shell Materials on Microstructure and Properties of Microencapsulated n-Octadecane

Microencapsulated n-octadecane phase change materials (PCMs) with polyurethane (PU) and resorcinol-modified poly(melamine-formaldehyde) (PMF) shells were synthesized through interfacial and in-situ polycondensation, respectively, and their microstructures and phase change, thermal stabilities, and anti-osmotic properties were evaluated. FTIR were performed to verify the quality of encapsulation of n-octadecane within two shell materials. Optical phase-contrast microscope and scanning electronic microscopy images indicate a perfect core/shell microstructure and compact polymeric shells of these microcapsules. Differential scanning calorimetry measurements demonstrate the high enthalpies for the melting and crystallization of the microencapsulated n-octadecane, while wide-angle X-ray scattering patterns have confirmed that the crystall inity of microencapsulated n-octadecane is identical with that of pure n-octadecane. Although the two microencapsulated PCMs have good phase change properties, the encapsulation ratio and efficiency of the microcapsules with PU shell are much higher than those of PMF shell. However, the microcapsules with PU shell exhibit good thermal stability but poor anti-osmotic property in comparison with those of PMF shell.