Polyethylene Glycol-Carbon Nanotubes/Expanded Vermiculite Form-Stable Composite Phase Change Materials: Simultaneously Enhanced Latent Heat and Heat Transfer

Abstract

Polyethylene glycol (PEG)-carbon nanotubes (CNTs) with expanded vermiculite (EVM) form-stable composite phase change materials (PCE-CPCMs) were constructed via the efficient synergistic effect between EVM and CNTs. The resultant material demonstrated simultaneously enhanced latent heat and heat transfer. The unique EVM pore structure and CNTs surfaces contributed to the form stability of PCE-CPCMs. The adsorption capacity was 77.75–81.54 wt %. The latent heat of the PCE-CPCMs increased with increasing CNTs content due to the decreasing inhibition effect of EVM and the increasing adsorption capacity of PEG, which was 83.9 J/g during melting and 104.2 J/g during solidification for PCE7.09. The pore confinement and surface EVM interactions inhibited the heat storage capacity of the PCE-CPCMs. Moreover, the inhibition effect on the heat storage capacity of PCE-CPCMs during the melting process was stronger than during solidification due to the crystallization-promoting effect. The heat transfer of PCE-CPCMs was significantly enhanced by the CNTs filler (0.5148 W/(m·K) for PCE7.09) due to the decrease in interfacial thermal resistance and the formation of rapid thermally conductive pathways. Fourier transform infrared spectroscopy, thermogravimetric analysis, and thermal cycles test results confirmed that the PCE-CPCMs exhibited excellent chemical compatibility, thermal stability, and reliability.

Applications of Sustainable Polymer-Based Phase Change Materials in Mortars Composed by Different Binders

“…From the observation of the data reported in Table 3, it is noticed that both the melting and crystallization processes taking place in the PEG component contained in the mortars occurred at lower temperatures then those of pure PEG, being the decrease in the temperature peak approximately of 13–17 °C for melting process and of 10–13°C for the crystallization one. The shift in melting and crystallization processes toward lower temperatures has already found in different similar studies [25,38,42,43,44,45,46,47,48]. It has been attributed to physical surface interactions (such as capillary forces, hydrogen bonds and surface adsorption) between PEG and the other different components of each mortar.…”

Mortars Containing Sustainable PCM’s for the Energy Efficiency of Buildings

“…The characteristic temperatures and the related latent heat capacities are summarized in Table 2. As reported in Table 2 and shown in Figure 4, the DSC curve observed for LS/PEG composites in both the melting and crystallization processes are shifted toward lower temperatures, probably due to surface interactions between PEG and the LS porous substrate [11]. In addition, as expected, differences between the melting and crystallization enthalpies of PEG and of PEG-stone composites was measured.…”

Thermal Conductivity of Polyamide-6,6/Carbon Nanotube Composites: Effects of Tube Diameter and Polymer Linkage between Tubes

“…We also compared the results of our EAM modeling with experimental data [9,36,37,38,39] in Figure 9. The EAM predictions for micron-sized CNTs are within the range of experimental data [9,36,37,38,39,40,41]. It is worth mentioning that the results presented in Figure 9 are for a CNT/polymer nanocomposite with random orientations of CNTs.…”

“…The full and dashed lines represent the results of EMA modeling for CNTs of length 1 and 5 μm, respectively. The markers represent experimental data by Yu et al [36], circles; by Yu et al [9], (squares); by Patti et al [37], diamonds; by Liu et al [38], upward triangles; by Deng et al [39], downward triangles, by Hong and Tai [40] (crossed squares), and by Song and Youn [41] (crossed circles).…”