Micro/nano encapsulation of some paraffin eutectic mixtures with poly(methyl methacrylate) shell: Preparation, characterization and latent heat thermal energy storage properties

This work is aimed to prepare, characterize and determine the latent heat thermal energy storage properties of micro/nano encapsulated paraffin eutectic mixtures (PEMs) with polymethylmethacrylate (PMMA) shell. The eutectic combination ratios and optimum melting temperatures of C17AC24, C19AC18, C19AC24 and C20AC24 mixtures were find out prior to the encapsulation processes. Four kinds of micro/nano capsules, PMMA/(C17AC24), PMMA/(C19AC18), PMMA/(C19AC24) and PMMA/(C20AC24), were synthesized effectively as novel encapsulated phase change materials (PCMs) via emulsion polymerization. The Fourier transform infrared (FTIR) spectroscopy analysis confirmed the polymerization reaction to be occurred around the PEM used as core material. The polarized optical microscopy (POM), scanning electron microscopy (SEM) and particle size distribution (PSD) analysis showed that the fabricated PMMA/PEM micro/nano capsules had spherical shape-appearances with micro/nano sizes. The differential scanning calorimetry (DSC) measurements revealed that the micro/nano capsules containing the highest PEM content had melting temperature range of about 20-36 °C and latent heat storage capacities of about 86-169 J/g. Thermogravimetry analysis (TGA) results verified that the encapsulated PEMs had good thermal reliability and chemical stability after repeated melting/freezing cycles for 5000 times. Furthermore, the synthesized PMMA/PEM micro/nano capsules had conceivable thermal conductivity values and reversible phase change behaviors.