Study On Preparation And Application Of Multifunctional Phase Change Composite Supported By Microcapsule/Skeleton

With the rapid development of countries around the world,traditional fossil fuels are increasingly exhausted,making energy issues become the focus of attention of all countries.With the intensification of energy crisis,phase change heat storage technology as a new energy supply mode has attracted more and more attention.Therefore,phase change materials are selected as the main research object in this paper,which can be prepared and modified to meet its application in solar energy storage,building energy conservation,cold chain transportation and thermal management system.However,phase change materials generally have the fatal defects of low thermal conductivity and easy leakage,which affect their practical application.Therefore,this paper adopts microcapsule technology and skeleton support technology respectively to modify the phase change material,improve its thermal conductivity and thermal stability,so as to optimize the performance of the composite phase change material.（1）In this experiment,dodecyl alcohol was used as the nuclear body and a new clean green methanol-modified melamine formaldehyde（MMF）as the shell.Through in-situ emulsion polymerization,MPCM composite microcapsule phase change material with a core-to-shell mass ratio of 14:3 was prepared to meet the needs of low temperature storage（0-40℃）.At the same time,the experiment further added 10wt%thermal conductivity filler（BN and CNT mass ratio is 1:1）to solve the defects of low thermal conductivity.The results showed that the thermal conductivity and latent heat of BCPCM were 0.584 W/m·K and 163.8 J/g,respectively.Thermal analysis further confirmed that the prepared BCPCM had high encapsulation efficiency,and its thermal stability was actually due to the strong interaction between the dodecyl alcohol core in the transition layer and the prepared MMF shell.The applicability of this new type of composite phase change material is verified due to the improved thermal conductivity and stability in the presence of the"linear surface"network structure.In addition,the material has significant temperature control capability in the practical application of battery packs,and it shows excellent storage reliability in the temperature range of 0-40℃.（2）Microcapsule technology has certain limitations,which can not solve the problems of easy leakage and low thermal conductivity at the same time,so this experiment chooses skeleton support technology to modify the phase change material.In this study,MXene@PEG/Mg（OH）₂ phase change composite was prepared by introducing MXene（Ti₃C₂T_x）skeleton into polyethylene glycol（PEG）and adding Mg（OH）₂,a green and efficient flame retardant.At the same time,the existence of MXene makes the membrane has electromagnetic shielding properties.The EMI SE value of 0.18mm MXene@PEG/Mg（OH）₂is up to 38.8 d B in the X-band frequency range,the enthalpy of phase transition is 153.72 J/g,and the thermal conductivity increases from 0.26 to 0.95 W/m·K.Importantly,due to the high flame retardancy of Mg（OH）₂ and the interlaminar capillary effect of MXene,liquid PEG can be locked into MXene@PEG/Mg（OH）₂ during solid-liquid phase transformation,which significantly enhances morphology stability and protects its covered articles at high temperatures due to its flame retardancy properties.It provides a new way of thinking in the field of microelectronic packaging.（3）Finally,considering the high thermal conductivity of the carbonized polypyrrole tube（PNT）,the cellulose/carbonized polypyrrole tube（SF@PNT）matrix film was prepared by vacuum filtration method as the supporting skeleton.Phase change material PEG and green flame retardant Mg（OH）₂ were added respectively to obtain the composite film with high thermal management and flame retardant performance.With a conductivity of 613 S/m,SF/PNT has Electromagnetic interference performance（EMI SE）,which is up to 34.2d B in the frequency range of the X-band,far superior to the commercial standard of 20 d B for most EMI materials.Thanks to the effective matrix（CNF-PNT）structure,the electromagnetic wave can be dissipated effectively.In addition,the composite has effective endothermic and exothermic properties in the range of 30～100°C.The enthalpy of phase transformation is 153.96 J/g,and the thermal conductivity increases from 0.26 W/m·K to 0.92 W/m·K.In addition,SF/PNTS exhibit significant flame retardancy and drip resistance due to the presence of Mg（OH）₂ and PNT networks during combustion,and this study shows promising prospects for PNTS to enhance the thermal conductivity and flame retardancy of PCM.In this paper,the three parts of the experiment content respectively from the microcapsule technology and skeleton support technology for the modification of phase change materials,at the same time due to the addition of flame retardant and skeleton itself has electromagnetic shielding properties,enrich and expand the application of phase change materials.