ZIF-8 Adsorbs Alkane Phase Change Materials And Encapsulates PVC Phase Change Capsules

In this paper,Zeolitic Imidazolate Framework-8(ZIF-8)was synthesized in methanol at room temperature.The organic linker is 2-methylimidazole and metal ions source is Zn(NO3)2.The structure and thermal stability of ZIF-8 was characterized by FTIR,XPS,XRD,TG and BET.The result shows that ZIF-8 was prepared successfully and had a good thermal stability and a huge specific surface area.The phase change composite of paraffin/ZIF-8 and octadecane/ZIF-8 was prepared by adsorbing in vacuum.The phase change composite was characterized by TGA,DSC,XPS,XRD,FIR.The result of TGA shows that the percentage composition of paraffin or octadecane in the phase change composite was about 40wt%or 30wt%.the paraffin or octadecane in the phase change composite has two weight loss process in TGA graph,which is different from pure paraffin and octadecane.The result of DSC shows that the enthalpy of phase change of paraffin/ZIF-8 and octadecane/ZIF-8 were 41.1J/g and 52.8J/g.the result of XRD,FIR and XPS show that there was no chemical action between phase change material and ZIF-8.the paraffin or octadecane was adsorbed on surface of ZIF-8 crystal.The inner paraffin or octadecane was restrained,which result that the inner paraffin or octadecane was not able to change phase at the melting point of phase change material.The phase change materials would leak after lots of thermal cycling,because the materials was adsorbed on the surface of ZIF-8 crystal.The PVC capsules were prepared using dual pore foaming method.PVC/octadecane composite phase change macrocapsules were prepared by adsorbing octadecane into cavity of capsules in vacuum.To prevent octadecane from leaking,ZIF-8 was synthesized on the surface of capsules.The result of FIR shows that ZIF-8 had been synthesized successfully.The enthalpy of phase change of PVC/octadecane composite phase change macrocapsules was 130-140J/g.the capsules has a potential application in building for energy conservation.But the leakage of phase change material had been not solved completely.