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Energy has become the key material basis of social development. In this work, liquid capric acid-paraffin was evenly adsorbed in the pore structure of expanded graphite (EG) by a physical adsorption method, and the new composite phase change material of capric acid-paraffin/expanded graphite (CA-P/EG) was prepared. The Fourier transform infrared (FT-IR) curves of CA-P/EG composites did not change after 1000 cycles, and there was no new characteristic absorption peak, indicating that CA-P/EG composites have good chemical stability. The results showed that the optimum content of CA-P/EG in a phase change energy storage gypsum board was 20%, and the wet bending strength and compressive strength were 2.42 and 6.45 MPa, respectively. The water absorption was 16.37%, and the apparent density was 1.410 g/cm 3 . In addition, the melting and freezing temperatures were 26.40 and 23.10 °C, and the latent heats of melting and freezing were 27.20 and 25.69 J/g, respectively. It was found that the gypsum board has excellent thermal stability after 400 times of melting−freezing cycling and that the heat storage capacity increases with the increase of the CA-P/EG content and the thickness of the gypsum board.

Capric acid-hexadecanol (CA-H) and capric acid-paraffin section (CA-PS) composite phase change materials were prepared by a melting−blending method, and two new composite phase change energy storage materials based on expanded graphite were obtained by the physical adsorption method. The results showed that the optimum mass ratio of CA-H and CA-PS were 74:26 and 81:19, respectively. It was found via FT-IR that CA, H, and PS acted together by molecular force without chemical reaction. The phase transition temperature of CA-H and CA-PS was 24.22 and 26.99 °C, respectively, and the latent heat of phase transition was 190.5 and 153.7 J/g, respectively. On the other hand, the best mass ratio of CA-H/EG and CA-PS/EG was 11:1 and 7:1, respectively. On the basis of SEM and FT-IR results, it was found that CA-H and CA-PS were uniformly distributed in the pores of EG by physical action; the melting and freezing temperatures are in the range of 21∼28 °C, and the latent heat was in the range of 133∼178 J/g by DSC. CA-H/EG and CA-PS/EG had good thermal and chemical stability after 1000 accelerated melting−freezing cycling tests. According to the TG and thermal storage experiments, CA-H/EG and CA-PS/EG had excellent heat resistance, and the high thermal conductivity of EG promoted the thermal storage and release rate of CA-H and CA-PS. Therefore, CA-H/EG and CA-PS/EG can be used as candidate materials in the fields of building energy savings.

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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.