Study On The Preparation And Hygrothermal Properties Of Nano-encapsulated Phase Change Material And Form-stable Composite Material

With the improvement of requirements for living environment comfort,the energy consumption of residential buildings was getting higher.In order to achieve the buildings' energy-saving,encapsulated thermal storage materials and moisture-conditioning materials were obtained people's attention.Presently,there were some weakness about the encapsulated thermal storage materials such as large particle size,none hydrophilic shell and poor compatibility.Furthermore,its application was limited.Therefore,in this paper,the performance of capsule material would be improved so that it was given heat storage and humidity control function.And then,a role of regulating the living environment was played by capsule material.Firstly,using n-octadecane as core material and the polystyrene as inner shell material and the hydrophilic butyl acrylate-methyl methacrylate as outer shell,the double-shell encapsulated phase change material(EPCM)was synthesized via miniemulsion polymerization.The hydrothermal properties of the synthesized EPCMs were tested by step cooling curve and desiccators' method.The results show that the process parameters of the optimal thermal and moisture performance are as follows: the content of emulsifier AOS is 3%wt,the mass ratio of core to inner shell and outer shell is 1?1.5?1,the content of initiator is 0.6%wt,the content of the crosslinkeris 0.8%wt(mass percentage of inner shell);the Ultrasound time is 20 min,the pre-emulsification speed is 2000rp/min,the pre-emulsification time was 45 min.And the maximum equilibrium moisture content is 0.41799kg/kg.The optimized EPCMs were characterized by nano-LPSA,DSC,TGA,FTIR,SEM and TEM.The results show that the EPCM is prepared with evenly distributed particle size in the nanometer scale(10~ 300nm),hydrophilic and rough surface,and with the double-layer and nano-spherical morphology.The phase transition temperature of NanoPCM is 29.54?;the enthalpy of change is 52.42J/g.Secondly,the shape-stabilized composite material was prepared with NanoPCM and diatomite and gypsum.And its physical mechanics and hydrothermal properties were tested and optimized.The results show that the shape-stabilized composite material with 15%wt NanoPCM and 15%wt diatomite and 0.6%wt polycarboxylate superplasticizer has better physical mechanics and hydrothermal properties than others,and its compressive strength is 2.51 MPa,phase transition temperature is 29.85?,enthalpy of change is 6.65J/g,the maximum equilibrium moisture content is 0.19496kg/m2.Furthermore,with the increase of the NanoPCM content and the diatomite content,the water paste ratio of the shape-stabilized composite material increased,and its bulk density and compressive strength decreased.However,its hydrothermal properties are favorable.Finally,the characterization and mechanism of the shape-stabilized composite material were analyzed by FTIR,MIP and SEM.The results show that the shape-stabilized composite material with the excellent physical mechanics and hydrothermal properties has small pore size distribution and few pores,and its inner packing is tight which is due to the pore filling of the NanoPCM.The results of the microscopic morphology are in agreement with the measured compressive strength and thermal and humidity properties.The thermal capacity is related to heat storage properties of NanoPCM itself and the absorption and desorption ability is related to the porous diatomite and NanoPCM with hydrophilic polymer surface and interface pores.Therefore,the hydrothermal properties of the shape-stabilized composite material are provided under the combined action of the diatomite,the NanoPCM and the interface pore to regulate the temperature and humidity of the environment.