Application of graphite platelets for heat transfer enhancement of cementitious composites containing microencapsulated phase change materials

The incorporation of microencapsulated phase change materials (MPCMs) is an effective method to increase the thermal energy storage (TES) capacity of cementitious composites. However, the thermal conductivity of cementitious composites will be reduced upon incorporation of MPCMs, which may reduce the latent heat activation of MPCMs. This study evaluated the effect of adding graphite platelets (GP) on the heat transfer performance of cement paste incorporating polystyrene/n-eicosane MPCM (CP-MPCM). The main purpose is to enhance the thermal conductivity of CP-MPCM, thus achieving faster heat storage and release rates. The cement samples containing different proportions of MPCM and GP were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermal conductivity measurement, and thermal cycling test. In the thermal cycling test, the samples were heated and cooled in the same temperature range (13-60 degrees C) to compare their average heating and cooling durations. The results showed that the addition of 5 wt% GP enhanced the thermal conductivity of CP-MPCM by 44.5-50.1%. The heat storage and release rates of CP-MPCM were improved by up to 25.3% and 23.8%, respectively. By adding 15 wt% MPCM and 5 wt% GP, the heat storage coefficient of pure CP was increased by 55.8%. Hence, the addition of GP can improve the utilization of the latent heat capacity of MPCMs in cementitious composites.