Study of Phase-Transition Characteristics of New Composite Phase Change Materials of Capric Acid–Palmitic Acid/Expanded Graphite

[Image: see text] A new composite phase change material of capric acid–palmitic acid/expanded graphite (CA–PA/EG) with the optimum mass ratio of EG equated to 8:1 was prepared by the physical adsorption method. It was observed that the eutectic point of CA–PA binary system was reached at 22.1 °C, and CA–PA was uniformly distributed into the pores of EG by physical interaction. The melting and freezing temperatures of CA–PA/EG obtained by differential scanning calorimeter (DSC) were 23.05 and 20.82 °C, respectively, while the corresponding latent heats were 139.7 and 131.8 J/g, respectively. It had good thermal and chemical stability, and there was almost no leakage of liquid binary phase change materials after 1000 melting–freezing cycles. According to the experimental results of the thermogravimetry (TG) analyzer as well as heat storage and release, CA–PA/EG has excellent thermal reliability and heat resistance and the high thermal conductivity of EG promotes the thermal energy storage and release rate of CA–PA. Thus, CA–PA/EG is suitable as a phase change energy storage material for building energy conservation.