Polyethylene Glycol-Calcium Chloride Phase Change Materials with High Thermal Conductivity and Excellent Shape Stability by Introducing Three-Dimensional Carbon/Carbon Fiber Felt

The low thermal conductivity and poor shape stability of phase change materials (PCMs) have seriously restricted their applications in energy storage and energy saving. In this paper, poly(ethylene glycol)-calcium chloride/carbon/carbon fiber felt (PEG-CaCl2/CCF) PCMs were fabricated by a liquid-phase impregnation-vacuum drying-hot compression molding method with carbon/carbon fiber felt as the three-dimensional (3D) thermal skeleton and PEG-CaCl2 as the polymer PCM matrix. PCMs were heated and compressed by the compression confinement method to improve the contact area between 3D skeleton carbon fibers. The carbon fibers in PCMs presented a 3D (X-Y-Z) network structure and the fiber arrangement was anisotropic, which were beneficial to improve the thermal conductivity of PCMs in the fiber direction. The compression confinement can improve the contact area between the fibers in the 3D skeleton. As a result, the thermal conductivity of PEG-CaCl2/CCF PCMs can reach 3.35 W/(m K) (in-plane) and 1.94 W/(m K) (through-plane), about 985 and 571% of that of PEG-CaCl2, respectively. Due to the complexation of PEG and CaCl2 and the 3D skeleton support of carbon fiber felt, PCMs have excellent shape stability. The paper may provide some suggestions for the preparation of high thermal conductivity and excellent shape stability PCMs.