Preparation And Properties Of Graphene Oxide-modified Phase Change Microcapsules

The problem of energy shortage is becoming more and more serious with the rapid development of the global economy.Phase change materials(PCMs)can absorb and release the latent heat during the phase change process,and achieve the effect of storing and releasing energy.It is one of the research priorities to alleviate the shortage of energy.Microencapsulation of phase change materials can solve PCMs' problems during phase change process such as leakage,corrosion,bad compatibility.At present,microencapsulated phase change materials(MEPCMs)with a polymer shell are more common.They have bad thermal conductivity,poor mechanical property,poor leakage-performance and low encapsulation capacity.Graphene possesses many excellent properties such as high thermal conductivity,good barrier property and mechanical property.As a precursor of graphene,graphene oxide(GO)is compatible with most polymers and is amphipathic to stabilize Pickering emulsion because of the hydrophilic oxygen-containing functional groups on its hydrophobic surface.In this study,the main conclusions were listed as follow:(1)GO was introduced into the melamine-formaldehyde resin(MF)prepolymer during the prepolymer preparation process,and MEPCMs with GO modified MF shell were prepared by in situ polymerization.The addition of GO can improve mechanical property of MEPCMs,but the excess GO can weaken mechanical property and encapsulation capacity of MEPCMs.The addition of GO can improve thermal conductivity of MEPCMs.When the concentration of GO dispersion is 3.0 mg/m L,the thermal conductivity increased by 65.0%.(2)Using the amphiphilic nature of GO,GO was introduced into the surface of paraffin emulsion microsphere by emulsification,then MEPCMs with MF as shell material and GO as impervious layer were prepared by in situ polymerization.The addition of GO can enhance leakage-performance of MEPCMs.When the concentration of GO dispersion is 0.5 mg/m L,the encapsulation ratio of MEPCMs is 93.89 wt%,and the leakage rate is 93.1%lower than that of unmodified MEPCMs.(3)The GO-coated paraffin MEPCMs were obtained by using theamphiphilic nature of GO,then MEPCMs with paraffin@reduced graphene oxide(r GO)core-shell structure were prepared by reduction.And a cellular segregated rGO network within paraffin was constructed through hot compression of the MEPCMs particles.The prepared paraffin@graphene MEPCMs have obvious core-shell structure,and the content of graphene in MEPCMs is 0.34wt%.The thermal conductivity of the MEPCMs and phase change materials with cellular segregated r GO network are increased from 0.125 W/(m·K)to 0.351 and 0.418W/(m·K),respectively.