Preparation and Application Study of Polymer Based Phase Change Materials

Author:Chen Yan Feng

Supervisor:huang hong

Database:Doctor

Degree Year:2019

Download:67

Pages:159

Size:8448K

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In view of the shortcomings of polymer medium composite phase change materials,such as low thermal conductivity and high addition amount,which lead to the large enthalpy reduction,the optimization and improvement work in this paper are carried out.In this paper,porous carbon materials with strong adsorption capacity blending with polymers wich are with good compatibility,obtaining reduction the proportion of addition polymers.What’s more,the polymer based phase change materials with high thermal conductivity,mechanical properties and enthalpy value are obtained.The specific work is as follows:1.Ordered mesoporous carbon material A-CMK-3 was prepared by calcination and used to obsorb paraffin RT44HC to obtain RT44HC/A-CMK-3 composite phase change material.In order to improve the mechanical properties of A-CMK-3 based composite phase change material,polyethylene(PE)with good compatibility with paraffin wax was used to composite with it.The thermal conductivity of calcined CMK-3 is 6.981W·m-1·K-1,which is 4.5 times higher than that of uncalcined CMK-3.The thermal conductivity of RT44HC/A-CMK-3composite phase change material is 10 times higher than that of pure paraffin.The optical absorption in visible region is 7 times higher than that of pure paraffin RT44HC,and it has great photo-thermal property.The storage and release rate of photo-driven thermal is 30 times higher than that of pure paraffin RT44HC.The tensile strength of the prepared PE-A-CMK-3based phase change material is 7.6 times higher than that of RT44HC/A-CMK-3 composite phase change material and 2 times higher than that of RT44HC/A-CMK-3 composite phase change material.However,the enthalpy of phase change,thermal conductivity and photo-thermal conversion properties decrease to a certain extent.The results show that the calcined ordered mesoporous carbon A-CMK-3 is an excellent adsorbing skeleton material for phase change materials.The composite phase change materials based on A-CMK-3 and PE-A-CMK-3 have great application potential in solar water heating system and solar heating building system.2.Based on work 1,a phase change material OP44/EG/PE-EPDM was prepared and used in building roof insulation heating.The phase change melting temperature of the composite phase change material is 41.5℃,the melting enthalpy is 143.8 J·g-1,the thermal conductivity is2.2 W·m-1·K-1,which is 4 times higher than that of pure paraffin(OP44),and the tensile strength and impact strength of the prepared OP44/EG/PE-EPDM composite phase change material are 7 times and 3 times higher than that of OP44/EG composite phase change material,respectively.Based on the experimental results,a numerical calculation model of composite phase change materials for building roof heating and insulation is established.When the thermal conductivity is lower than 0.1 W·m-1·K-1,it can maintain better thermal insulation performance;increasing the thickness of composite phase change material can slightly increase thermal resistance;phase change temperature at 40℃is the most appropriate for roof thermal insulation.3.Based on work 2,the interaction modes and compatibility rules of components in the polymer phase change material system are explored.The influence law of solid behavior was explored and optimized the material selection and proportion of each component of polymer phase change material(polymer+porous carbon material+paraffin+functional filler),and the polymer based phase change material system with good compatibility was obtained,which provided theoretical guidance for the preparation of polymer phase change material.(i)When the mass ratio of PE to EPDM is 25%:5%,the prepared PE-EPDM/EG-based composite phase change materials have excellent mechanical properties,in which the tensile strength is 8.1 MPa and the flexural strength is 14.7 MPa;the thermal conductivity of the composite phase change materials is 2.08 W·m-1·K-1 and the enthalpy of phase change is 139 J·g-1.Ethylene propylene diene rubber(EPDM)can improve the compatibility of the components of the composite phase change material system,including polyethylene,paraffin and expanded graphite.The excellent compatibility of the composite system is conducive to improving the dispersion uniformity of expanded graphite,thus improving the synthesis of PE-EPDM/EG based composite phase change material.(ii)Adding carbon nanotubes to PE-EPDM/EG composite phase change material system.When the mass fraction of CNT was 5.4%,the thermal conductivity reached at 3.112 W·m-1·K-1;10.19 MPa in tensile strength and 21.48 MPa in flexural strength;64.5 and64.2℃in melting temperature and 130.3 and 130.5 J·g-1 in enthalpy of melting and solidification,respectively.(iii)A flame-retardant PE-EPDM/EG-based composite phase change material was proposed and applied to the thermal management system of lithium-ion battery modules.The flame retardant grade of the prepared polymer phase change materials reaches V-0 when the flame retardant content reaches 30%.The melting temperature and enthalpy of phase change of the prepared composite phase change materials are 41.5℃and112.2 J·cm-3 respectively,the thermal conductivity is 1.0 W·m-1·K-1,and the impact strength is1.92 kJ·m-2.4.Further,a flexible block olefin copolymer(OBC)polymer-based composite phase change material was prepared to meet the application scenario of high tensile,bending and impact properties.The melting temperature and enthalpy of phase change of the prepared polymer phase change materials are 65.04℃and 144.1J·g-1,respectively.The thermal conductivity is 1.905 W·m-1·K-1,and the tensile strength is 3.7MPa.Good thermal conductivity can absorb a large amount of solar radiation,fast photothermal response time,photothermal efficiency and light receiving efficiency.They have great potential for application in solar photothermal utilization.