Preparation And Property Of Paraffin Phase Change Microcapsules With Calcium Carbonate Shell

The efficient use of renewable energy has attracted a great deal of interest due to the reduction of traditional fossil fuels and the incr easing emission of greenhouse gases.Phase change materials?PCMs?,as a kind of thermal energy storage,has attracted more and more attention due to its effective use of environmentally friendly energy.Microcapsule phase change materials?Microencapsulated phase change materials,MEPCMs?can achieve a shape-stable structure that overcomes the limitation of PCMs,which helps to broaden the practical field.In view of the shortcomings of organic wall microcapsule phase change materials such as poor thermal conductivity,mechanical properties and unsatisfactory compatibility with building materials,and considering the inorganic materials,which possess good heat transfer performance,durability and good compatibility of building materials.In this paper,paraffin was used as the core material and calcium carbonate as the shell to synthesize the inorganic shell phase-change microcapsules,and the microcapsules were modified by graphene oxide.The main work is as follows:?1?Styrene-maleic anhydride?SMA?,sodium dodecyl sulfate?SDS?and sodium dodecyl benzene sulfonate?SDBS?were respectively used as emulsifier,and changing the p H value of the reaction system to obtain a series of paraffin phase-change microcapsules with a calcium carbonate?Ca CO ₃?shell.Morphology,microstructure and properties of MEPCMs were performed by scanning electron microscopy?SEM?,X-ray diffraction?XRD?,Fourier transform infrared spectroscopy?FT-IR?,differential scanning calorimetry?DSC?,thermal conductivity test and paraffin leakage rate test.The results show that the paraffin is successfully coated by calcium carbonate,and the formed Ca CO3shell has two crystal phases,vaterite and calcite.MEPCMs encapsulated rate is66.0%,leakage rate is 2.01%at 50?,indicating that MEPCMs have excellent phase transition properties and high thermal energy storage capacity.The melting temperature and latent heat of MEPCMs were 57.0?and 170.03 J/g,respectively.The encapsulation efficiency depend on the p H value of the reaction system and emulsifier type.The type of emulsifier also affects the crystalline phase of the calcium carbonate shell.The thermal conductivity of the MEPCMs is significantly improved due to the coating of the shell with high thermal conductivity.?2?The environmental friendly phase change microcapsules?MEPCMs?with calcium carbonate shell were modified by graphene oxide?GO?,and the effects of GO addition concentration and adding method on MEPCMs were also discussed.The core-shell structure and Ca CO₃ shell morphology of MEPCMs were confirmed by SEM,FTIR and XRD.Thermal property and thermal stability of MEPCMs were investigated by DSC and thermogravimetric analysis?TG?.The results show that adding GO can improve the heat storage capacity and thermal stability.When GO was used as co-emulsifier and the content was 1.0wt%,the maximum encapsulate ratio of MEPCMs was about 73.19%,which was much higher than the phase change microcapsules with inorganic shell.Paraffin leakage rate tests showed that the microcap sules modified with GO can reduce the leakage rate up to 89.6%compared with the microcapsules without GO.Compared with pure paraffin,the thermal conductivity of MEPCMs can increase up to 86.7%.When MEPCMs were modified by GO as an emulsifier,the properties of MEPCMs obtained were better than the phase change microcapsules obtained by separately adding GO.And the mechanical properties of MEPCMs and light-to-heat conversion efficiency has also been improved with GO added.The ideal latent heat storage,thermal stability,thermal conductivity,mechanical properties and leakage-prevention property make GO modified paraffin phase change microcapsules with Ca CO₃ shell have broad application prospects in green energy.