Influence of gelatinization conditions on thermal properties of shape-stabilized phase change materials for thermal energy storage

According to gelatinization principle, PEG/SiO2 shape-stabilized phase change materials (SS-PCMs) were prepared by temperature-assisted sol-gel method and countra-ion coagulant-assisted sol-gel method in thermodynamic instability and countra-ion coagulation. The influences of gelatinization conditions on phase change enthalpies and temperature of SS-PCMs were studied by DSC, XRD and FT-IR. The results show that enthalpies of PEG/SiO2 SS-PCMs prepared by temperature-assisted sol-gel method are 36.1~128.4 J/g, which are lower than that of pure PEG with the same mass fraction; and phase change temperatures are slightly lower. For PEG/SiO2 SS-PCMs, the interaction between PEG and SiO2 is physical mechanism. The phase transition behavior of PEG is mainly reflected in drag effect of inside and outside interfaces of SiO2 and steric effect of SiO2 mesoporous structure. Enthalpies of Ca-PEG/SiO2 SS-PCMs prepared by countra-ion coagulant-assisted sol-gel method are 32.6~91.5 J/g, the corresponding enthalpy loss rate is high and phase change temperatures are increased. For Ca-PEG/SiO2 SS-PCMs, the enthalpies are severely damaged because the molecular conformation and crystallization structure of PEG are changed due to formation of the coordinate bond between O of PEG C-O-C and Ca2+. Of course those enthalpies are also affected by the physical action of SiO2. That is, the gelatinization conditions determine the interaction mechanism among components of SS-PCMs and influence the thermal properties of PEG/SiO2 SS-PCMs. The analysis results show that temperature-assisted sol-gel method is more appropriate method to prepare PEG/SiO2 SS-PCMs than countra-ion (CaCl2) coagulant-assisted sol-gel method. ©, 2015, Chengdu University of Science and Technology. All right reserved.