Effect of encapsulation and additives doping on the thermophysical properties of erythritol for thermal energy storage

Abstract

We wished to improve the thermophysical properties and thermal stability of meso-erythritol (ET) for storage of thermal energy. Hence, capsules containing ET with polysiloxane (pSiO) shells were fabricated using ultraviolet-assisted in situ polymerization, and the effects of encapsulation and additives doping on the thermophysical properties of ET were studied. Differential scanning calorimetry showed that the heat-release performance of the composite (pSiO-C-A@ET) upon addition of 3.0 wt. % carboxymethylcellulose (CMC) and 9.0 wt. % nano-α-Al2O3 increased significantly from 64.1% to 89.0%, and the supercooling degree decreased dramatically from 89.5 °C to 17.0 °C, compared with that of pure ET. Spectroscopy (Fourier transform-infrared, x-ray diffraction) implied no change in the crystal structure of ET after encapsulation by pSiO shells. Addition of a nucleation agent (nano-α-Al2O3) and thickening agent (CMC) had no effect on the crystal structure of pSiO-C-A@ET. The thermal conductivity of pSiO@ET and pSiO-C-A@ET capsules increased by 6.2% and 20.0% compared with that of pure ET (0.65 W/m·K) at 25 °C, respectively. The thermal conductivity was enhanced noticeably by doping with nano-α-Al2O3. Results from accelerated thermal cycling suggested that pSiO@ET and pSiO-C-A@ET capsules exhibited good thermal stability and thermal durability. These data suggest that composite phase-change materials could be employed for applications involving storage of thermal energy.