| Phase change materials (PCMs) are the energy storage materials that are able to absorb or release large quantities of energy at a constant temperature by undergoing a change of phase. Owing to the merits of high thermal energy storage densities, stable temperature, controllable process and multiple recycling, they have been the focus of research on energy-saving and material science. A novel and efficient energy-saving building insulation materials can be prepared by incorporating PCMs into traditional insulation materials, which have promising economical and environmental benefits. To date, however, the mostly investigated organic PCMs are unary and binary composite PCMs, which have a leakage problem after the adsorption in porous materials. In this paper, phase change energy storage composite materials were prepared by using expanded perlite as substrate to absorb multiple organic PCMs, which were capped with fine bentonite.The phase change performance of organic PCMs has been studied. Four systems, such as organic acid-organic acid, alcohol-organic acid, alkyl-acid and alkyl-alcohol, can form eutectic, with phase change temperatures between the melting points of two substances. The eutectic temperature of many groups of binary eutectic mixture is in the range of temperature for human comfort, which permits their utilization as building material.The ternary system was formed by introducing a third substance in the binary system of higher melting point PCMs. The latent heat value slightly changed, but the phase change temperature greatly decreased. Therefore, it overcomes the deficiency of the binary eutectic with higher phase change temperature which can not be used as building material. The binary eutectic mixture was formed at the mass ratio of Laurie acid (LA)/Palmitic acid (PA)=76/24. The lowest eutectic point and the latent heat value are 31.7℃and 272.9 kJ/kg, respectively. The ternary eutectic system of Laurie acid/Palmitic acid/Myristic acid (MA) can be formed at the mass ratio of LA/PA/MA=60.8/19.2/20. The eutectic temperature and the latent heat value are confirmed as 26.9℃and 264.2 kJ/kg, respectively. That is to say, the latent heat value of the ternary system is 8.7 kJ/kg lower than that of the binary system, and phase change temperature decreased by 4.8℃. The latent heat values of the eutectics before and after introducing LA formed at the mass ratio of hexadecanol (H)/Palmitic acid (PA)= 6/4 are 204.18 kJ/kg and 179.63 kJ/kg, respectively, and the phase change temperature decreases from 43.1℃to 26℃. The latent heat values of the eutectic before and after introducing LA at the mass ratio of H:PA=7:3 are 195.28 kJ/kg and 177.87 kJ/kg, and phase change temperature decreases from 44.7℃to 27℃.The composite PCMs of LA/PA/MA/EP and H/PA/LA/EP were prepared by vacuum adsorption of ternary organic PCM within the EP. The phase change temperature and the latent heat values are 28.55℃and 25.77℃,79.45 kJ/kg and 80.49 kJ/kg, respectively. They can be used as building material with high latent heat values and comfortable phase change temperature. The phase change temperature of phase change energy storage composite materials of LA/PA/D/EP is 25.3℃,which is 10℃lower than that of LA/PA/EP. After 200 thermal cycles, the latent heat values of melting and freezing is 62.91 kJ/kg and 61.9 kJ/kg, respectively.The mass loss of phase change energy storage composite materials based on expanded perlite capped with fine bentonite is less than 1% after 300 thermal cycles. Thus, the melted PCM leakage can be inhibited successfully.Scanning electron microscope (SEM), Fourier transform infrared (FT-IR) techniques and durability characterizations show that ternary organic phase change material are uniformly dispersed in the pores of expanded perlite, and the phase change composite materials have good thermal stability and duravility after multiple melting-freezing cycles.
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