Preparation and characterization of modified activated carbon-based shape stabilized eutectic phase change materials for gypsum composites application

Abstract

Modified SAT-urea eutectic salts (EPCM) as the phase-change materials were prepared using modifiers such as disodium hydrogen phosphate dodecahydrate (DHPD) and carboxymethyl cellulose (CMC). The support material, hydrophilic modified activated carbon (MAC), was prepared using OP-10 as a hydrophilic modifier. The vacuum impregnation method was used to fabricate the MAC-based shape-stabilized eutectic phase-change materials (SSEPCM). The gypsum-based building materials with thermal storage capacity were obtained by compositing surface-treated SSEPCM and gypsum. The surface contact angle, surface functional group, phase transition temperature, latent heat, phase composition, and microstructure of the SSEPCM were examined using the static contact angle meter, Fourier infrared spectrometer, in-situ infrared spectrometer, differential scanning calorimeter, X-ray diffractometer, and scanning electron microscope. The adsorption capacity of MAC increased first and then decreased with the increase of OP-10 content in the modified solution. When the OP-10 content was 0.3 wt%, the contact angle between the surface of MAC and water reduced to 0°, and the mass fraction of EPCM relative to MAC was 93.1 wt%. The results showed that the OP-10 had a good hydrophilic modification effect on the granular activated carbon. The X-ray diffractometer and differential scanning calorimeter results of SSEPCM indicated that there was no chemical reaction between EPCM and MAC, the phase transition temperature was 32.11 °C, and the latent heat was 103 J/g. The latent heat loss rate of SSEPCM was 5.8 % after 100 thermal cycles, and the number of –OH did not decrease during the heating process of SSEPCM, which showed that SSEPCM had good thermal stability. The flexural and compressive strength values of the SSEPCM/gypsum composites were 2.50 MPa and 7.36 MPa, respectively, when 45 wt% SSEPCM was incorporated into the gypsum matrix, which was sufficient for practical applications. The introduction of SSEPCM could slowly reduce the thermal conductivity and significantly improved the thermal inertia of the composites.