Preparation,Characterization,Modification And Thermal Storage Properties Of Microencapsulated Phase Change Materials Using Acrylic Resin Copolymers/n-dodecanol

With the deepening of the energy saving and emission reduction concept,people are paying more attention to new energy saving and storage technologies.Phase change material(PCM)has high energy storage density and approximately constant phase transition temperature,which has been widely used in building temperature control,solar energy utilization and other fields.The microencapsulated phase change material(MPCM)technology is a novel energy storage technology that insulates the influence of phase change materials on the outside,present its energy storage advantages,and effectively controls the volume change of phase change process.Therefore,the preparation,characterization,modification of the formaldehyde-free MPCM and the investigation of the heat storage and temperature regulation characteristics of the phase change composite building materials has been investigated in this paper.The results can provide theory and data supports for application of MPCM.In this paper,MPCM containing acrylic acid as the shell material and n-dodecanol as the core material was prepared by suspension polymerization method and ultrasonic irradiation.In addition,the graphene(GR)and graphene oxide(GO)were introduced to modify the MPCM.The effects of GR and GO on the physical properties of modified MPCM were investigated by SEM,TGA,FT-IR,etc.A series of tests were carried out by preparing the cement-based composite building materials containing PCM by microencapsulation method and direct addition method.The results are as follows.(1)The MPCM prepared by the method above have clear coating behavior,and the core material does not react with the shell material during the coating process.Highspeed emulsification and the aid of ultrasonic irradiation make the MPCM have features of spherical shape,uniform particles,smooth surface and small particle size.The diameter of the microcapsules is about 1 ?m.The latent heat of MPCM reached 93.31 kJ/kg,the actual coating efficiency of microcapsules is 43%,and the subcooling is as low as 2.13°C.This MPCM can remain stable in the range of 0-100°C without leakage,which has high energy storage potential and practical application value.During the preparation of MPCM,as the increasing of emulsifier concentration,the MPCM shape tends to spherical and the adhesion between the microcapsules decreases.(2)For GR-MPCM,the addition of GR has slight effect on the microscopic morphology of microcapsules.GR is mainly connected with MPCM in the form of adhesion,the diameter of the GR-MPCM is about 0.7-1?m.However,the addition of GO has a great influence on the appearance of MPCM.The diameter of the GO-MPCM is increase to 10-20?m.The addition of GR and GO did not affect the basic chemical structure of the MPCM.(3)The initial phase transition temperature of GR-MPCM and GO-MPCM is earlier than that of MPCM about 2.4? and 4?,respectively.this result indicated that the addition of GR and GO can improves the thermal conductivity of microcapsules.The latent heat of GR-MPCM is 56.85 kJ/kg,which is about 39% lower than that of MPCM,while the latent heat of GO-MPCM is 135.6 kJ/kg,which is about 45% higher than that of MPCM.The initial decomposition temperatures of GR-MPCM and GOMPCM reach to 140?,which is higher than MPCM.The content of GR slight effect the mechanical strength of the microcapsules,breakage rate of microcapsule is about 10.1%.The content of GO was positively correlated with the mechanical strength of the microcapsules,when the GO content is 2.5%(relative to PCM),the breakage rate of GO-MPCM fell to 5.2%.(4)In the molding process of composite building materials,the type and amount of composite materials influence the reaction process.The effective energy storage components in concrete-based building materials are barely loss at room temperature,and the MPCM-concrete have higher thermal stability than PCM-concrete.At the same mass fraction of the composite components,the strength of the PCM-concrete is slightly lower than that of the MPCM-concrete,and the density of the composite building material decreases as the content of the PCM and MPCM increases.(5)The MPCM-concrete and the PCM-concrete both have the effect of energy storage and temperature regulation within a certain additive content range.With the range of the additive content ranging from 4% to 12%,the optimum microcapsule content of MPCM-concrete is 4%,and the optimum content of PCM-concrete is 12%.When the mass content of the composite component is 4%,the PCM-concrete has better temperature regulation performance,but its cycleability is poor,with the process of thermal cycling,the internal PCM content is losing and the PCM-concrete is irritating odors.The factors above limited practical application of PCM-concrete.