Preparation,characterization And Thermal Performances Of Polyethylene Glycol-Based Shape-Stabilized Phase Change Materials For Heat Storage

As the energy crisis has become more and more serious,people are devoting to developing alternative energy sources and new energy storage technologies.The phase change materials for energy storage store or release energy by latent heat from the phase change process.As a result,the phase change materials can achieve the aims of temperature control and energy saving.The phase change materials can also solve the problem that the energy doesn't match in space and time.Therefore,the phase change materials are attracting people's great concerns.In particular,the shape-stabilized phase change materials have become one of the most promising energy storage materials because of their having the advantages of both solid-liquid phase change energy storage materials and solid-solid phase change energy storage materials.In this paper,the three series of polyethylene glycol-based composite phase change materials?PCMs?were prepared by the physical blending method,using polyethylene glycol?PEG?as phase change materials and the carbon foam,diatomite and montmorillonite as supporting materials.The pure PEG,matrices and as-prepared PCMs were characterized by means of scanning electron microscope?SEM?,X-ray diffraction?XRD?,the nitrogen adsorption and fourier transform infrared?FTIR?spectra.And the thermal performances were investigated by differential scanning calorimetry?DSC?and thermogravimetric analysis?TGA?techniques.It is found that there is some leakage of the liquid phase when the weight percentage of PEG in the composite PEG/carbon foam PCMs was higher than 90 wt%.The maximum mass fractions of PEG in the PEG/montmorillonite and PEG/diatomite composites are respectively 60wt% and 55wt%,which could maintain the solid state above the melting point of PEG.The characterization results show that there are the only simple physical interactions between PEG and matrix materials.For PEG/carbon foam composite phase change materials,the phase change temperatures are increased with the increase of molecular weights of PEG,while the phase change enthalpies are first increased and then decreased.The PEG4000/carbon foam composite phase change materials have the highest melting enthalpy,which reaches168.5 J·g^-1.The phase change temperatures and enthalpies of PEG4000/carbon foam PCMs are increased with increasing the PEG mass fractions in the composites.For the PEG/diatomite composite phase change material with 55wt% of PEG,its melting and solidifying enthalpies are 76.9 J·g^-1and 80.5 J·g^-1,and its melting and solidifying points are 27.5 ? and 51.5 ?,which changes slightly?0.3 ? and 0.4 ??compared with those of pure PEG.For the 60wt% PEG/montmorillonite composite phase change material,its melting enthalpy is 95.1 J·g^-1 and its phase change temperatures and enthalpies are increased with the increase of mass fractions of PEG,but the phase change temperatures are lower than those of pure PEG.polyethylene glycol-based composite phase change materials have the thermal cycling setting ability.All the polyethylene glycol based composite PCMs in this study have good thermal cycle and thermal stability.The samples still can remain the shape stabilization after 200 thermal cycles.Moreover,there are almost no changes of the phase change temperatures and enthalpies before and after thermal cycles.All the samples have no thermal decomposition below 200 ?.