Fabrication and thermal properties of CaCl2·6H2O–CO(NH2)2/SiO2 as room-temperature shape-stable composite PCM for building thermal insulation

Abstract The combination of room-temperature phase change materials (PCMs) and building materials can reduce the energy consumption of heating equipment and improve indoor thermal comfort. In this paper, the novel CaCl2·6H2O–CO(NH2)2/SiO2 room-temperature shape-stable composite PCM was fabricated by melt-blending method with CaCl2·6H2O as the basic PCM, CO(NH2)2 as the phase change temperature regulator and hydrophilic fumed silica (SiO2) as the carrier. The temperature-regulating effect of CO(NH2)2 on CaCl2·6H2O and the shape-stabilizing effect of SiO2 on CaCl2·6H2O–CO(NH2)2 PCM were emphatically analyzed. The results revealed that the obtained composite PCM with 6% CO(NH2)2 and 20% SiO2 possessed a favorable form-stability, relatively high enthalpy (114.3 J g-1) and appropriate phase change temperature (21.03 °C) which decreased by 7.81 °C compared with pure CaCl2·6H2O (28.84 °C). Furthermore, its small supercooling degree (0.259 °C), low thermal conductivity (0.3667 W·m-1·K-1) as well as the excellent cyclic reliability and thermal stability indicated that the composite PCM has good thermodynamic properties, enabling its application for indoor building thermal insulation and even some other areas.