Characterisation of commercial phase change materials with potential application in gypsum boards for buildings

Abstract

Summary Currently, there is an expanded utilisation of lightweight construction structures in buildings, which results in a low structure's thermal storage capacity of the envelope due to the application of thermally unsuitable materials. PCMs incorporated into building structures components are potential alternatives to manage the inadequate thermal energy storage capacity of lightweight structures. To provide a guide for selecting and applying commercial PCMs in construction, nine organic and inorganic bulk materials were selected, and their thermophysical properties were characterised. Thus, the enthalpy of melting/crystallisation, the melting/crystallisation temperature, the stability of 50 cycles, and the verification of the presence of the subcooling phenomenon by DSC and the T‐history method were evaluated. Since the adequate methods to incorporate the PCMs in gypsum are suspension and vacuum impregnation, their thermal properties, together with density and viscosity, need to be considered, properties that are not typically reported in the datasheets of commercial PCMs. Furthermore, the temperature dependence of the viscosity and density of the solid/liquid PCMs were measured by a rheometer and densimeter/pycnometer, respectively. Based on liquid and solid density values, the volumetric expansion of PCMs during the melting process was calculated. Finally, the characterisation parameters were compared with those provided by the suppliers of the different companies. The characterisation's results indicate that for both organic and inorganic PCMs, the fusion temperature (21°C‐26°C) and the density values (0.777‐1.515 g/cm3 for liquid state and 0.895‐1.860 g/cm3 for solid state) were consistent with the values provided in the datasheet from the suppliers'. Viscosity values were found to be higher than expected, and the enthalpy was found to be lower (19%‐30%) when compared with the technical datasheets from manufacturers'. The cycling stability study results were consistent only for the organic samples, without displaying phase segregation or subcooling problems. Based on the thermophysical characterisation, it was possible to establish that three organic RT‐21, RT‐21(TA), RT‐25, and three inorganic SP‐21E, PCM 21C, HS‐24P PCMs would be suitable products for their inclusion into gypsum boards under the conditions analysed. These findings provide new insights regarding the applicability and development of new strategies and materials for passive or active heating/cooling applications in buildings.