Fabrication and characterization of poly(melamine-formaldehyde)/silicon carbide hybrid microencapsulated phase change materials with enhanced thermal conductivity and light-heat performance

A new type of microcapsule based on n-octadecane core and poly(melamine-formaldehyde)/silicon carbide (PMF/SiC) shell was designed for near-infrared light harvesting, light-heat conversion, thermal energy storage and heat-transfer enhancement. A series of hybrid microcapsules were successfully synthesized through in situ polymerization in an oil-in-water emulsion stabilized by sodium salt of styrene-maleic anhydride copolymer and SiC synergistically. The scanning electron microscopic investigation revealed that the microcapsules presented regular spherical morphology. The chemical compositions and crystalline structures of the resultant microcapsules were characterized by energy-dispersive X-ray, Fourier transform infrared spectroscopy and X-ray powder diffraction, confirming that SiC nanoparticles have been embedded in the PMF shell. Thermogravimetric analysis and a temperature-regulated test indicated that the prepared microcapsules possessed high thermal stability and good thermoregulating ability. Differential scanning calorimetry examination showed that the resulting hybrid microcapsules can maintain high effective core content and high encapsulation efficiency, and the supercooling crystallization was obviously suppressed after the incorporation of nano-SiC. Compared with PMF microcapsules, thermal transfer properties of the PMF/SiC microcapsules were significantly improved, and the thermal conductivity increased by 60.34% after the addition of 7% nano-SiC. Furthermore, the synthesized hybrid microcapsules effectively absorbed near-infrared light and demonstrated good photothermal conversion performance under light radiation.