Form-stable phase change materials enhanced photothermic conversion and thermal conductivity by Ag-expanded graphite

Phase change materials (PCMs), which exhibit significant capacity of latent heat absorption and release during the phase change process, have been promisingly used for solar energy conversion and storage. However, the application of organic PCMs for solar energy storage remains a great challenge owing to their low thermal conductivity and liquid leakage problem. In this work, a form-stable PCM with polyethylene glycol (PEG) and epoxy resin (EP) was prepared by melt blending (the mass ratio is 1:1). The experimental results indicated that the leakage problem of PEG was solved by the cross-linking of the molecular chains of PEG and EP. Meanwhile, in order to improve the solar energy conversion capability and thermal conductivity, an extremely low loading (4 wt%) of expanded graphite (EG) modified with Ag nanoparticle was added into the PEG/EP matrix. The results suggested that Ag nanoparticles were uniformly dispersed by electroless silver plating in the surface of EG, and the electroless modified EG was evenly distributed in the PEG/EP matrix. Moreover, the composite fillers exhibited prominent solar energy conversion capability (90.7 %) and higher thermal conductivity (121 %). Therefore, this novel composite has favorable potential in practical applications of solar energy storage.