Preparation And Performance Evaluation Of Binary Composite Phase Change Material Of Normal Temperature

With the development of logistics industry recently, higher requirements are put forward for temperature sensitive products under the condition of transportation. In order to ensure that every link of storage and transport in a state of controlled temperature, it is particularly important for passive control temperature packaging applied to controlled temperature logistics, therefore received widespread attention in engineering. As the basis of controlled temperature packaging, phase change materials can store and release energy, so that it makes the ambient temperature maintain at the same temperature, making full use of energy.Solid-liquid phase change material easily let out, so the preparation of shape-stabilized phase change material was considered. There existed supercooling and phase separation problems in inorganic hydrated salts, so it was needed to add suitable additives to solve it. Consdering these problems described above, the main contents and results are as follows:（1） Composite phase change materials were prepared using two kinds of fatty acids of capric acid and palmitic acid（CA-PA） with MCM-41, Si₃N₄, expanded graphite or active carbon as supporting materials by the way of vacuum absorbing. The chemical component of composite PCMs was observed by FT-IR, microstructure of the surface by SEM, thermal physical performance and accelerated cycling performance by DSC. It was analysed that the fatty acids CA-PA were only chimera simply and not reacted chemically. Besides, CA-PA could be absorbed into supporting materials. What’s more, it was indicated that shape-stabilized phase change materials had good heat storage performance and cycling stability.（2）Inorganic mixed salts were prepared by Na2HPO4·12H2O and Na2SO4·10H2O with several different kinds of additions such as anti-cold agent, anti-phase separation agent,water-retaining agent, nano materials, porous materials, occuring phase change at normal temperature, receiving high latent heat of fusion. Besides, the thermal physical performance and the coefficient of thermal conductivity were tested. It was concluded that 3wt%Na2Si O3·9H2O and 3 wt% Ti O2 could reduce the degree of supercooling of inorganic mixed salts. Besides, the thermal conductivity was enhanced by adding nano materials, saving the whole crystal time, improving the efficiency of energy storage; nano-crystalline cellulose which increased the viscosity of solution, could be used as a nucleating agent alone, but might work with Na2 Si O3·9H2O. 2wt% CMC accorded with the processing condition, with low cost.Expanded graphite and active carbon maintained the morphology of inorganic salts,preventing the leakage of liquid.（3）The temperature-control effect of CA-PA-nano Si₃N₄ was studied in EPS thermal insulation box; the insulation effect was reflected by the change of the temperature in the incubator. It turned out that the temperature in EPS thermal insulation box could be within26.5℃ after 12 h in constant temperature of 45℃ displaying better thermal insulation.