Preparation And Properties Characterization Of Shaped Phase Change Thermal Storage Wood Plastic Composites

Wood plastic composite（WPC）is a new type of environment-friendly green material with the advantages of easy forming,good dimensional stability,non-toxic and tasteless,moth proof and corrosion-resistant.WPCs are gradually used in the field of furniture and construction,with a very broad prospect.However,the function of WPC is relatively single,and green phase change thermal storage material（PCM）can achieve energy-saving and temperature regulation through the transformation of phase state.The introduction of green PCMcan give wood plastic composite a new function,which can realize the response of WPC to the environment temperature and the efficient storage and transformation of thermal energy.It is of great significance for the development of new bio based green energy-saving materials.Therefore,in this paper,the shaped PCMis taken as the research object,the preparation and performance research of porous and microencapsulated phase change energy storage materials are carried out,porous and microencapsulated phase change energy storage materials with high energy storage density and excellent thermal physical properties are designed,and the functional materials of PCMand wood plastic composite are constructed.Starting from the phase structure of the matrix,the performance of the shaped phase change energy storage wood plastic composite was characterized,and the energy storage mechanism of the shaped phase change energy storage wood plastic composite was further explored,and the thermal storage and release performance simulation of the shaped phase change energy storage wood plastic composite was carried out.The main conclusions are as follows:（1）Porous phase change energy storage materials were prepared by vacuum adsorption method,which was based on the expanded graphite（EG）which was used as the shaped matrix material and the polyethylene glycol 800（PEG 800）which was used as the phase change material.The phase change temperature range of PEG/EG phase change energy storage materials was 18.89℃～34.23℃,which was in the comfortable temperature range of human body,and the phase change latent heat values were97.56 J·g^-1 and 98.59 J·g^-1 in the crystallization and melting range.The thermal storage and release rate increased by 27.31%and 60.5%in the process of heating and cooling.The combination of EG and PEG800 was achieved by hydrogen bond and capillary adsorption,which limited the scope of molten PEG and prevented the leakage of liquid.The high thermal conductivity of EG can reduce the supercooling of PEG 800.（2）The unitary microencapsulated PCM with polyurethane as wall material and PEG 800 as core material was prepared by interfacial polymerization.The binary microencapsulated PCM with polyurethane as wall material and PEG 800 and PEG 1000 as core material was designed and synthesized.Both unitary and binary microencapsulated PCMs had positive resistance and thermal stability.In the crystallization process,the phase change latent heat values of unitary and binary microencapsulated PCMs were 109.6 J·g^-1 and 97.19 J·g^-1,which were 96.6 J·g^-1 and 98.58 J·g^-1 respectively in the melting process.The phase change temperatures of unitary and binary microencapsulated PCMs were 25.51℃,23.12℃and 28.02℃,38.10℃,32.88℃and 36.24℃in the process of crystallization and melting,which were in the comfortable thermal environment temperature range of human body.The temperature rise and fall time of binary microcapsule PCMwas longer,and the heat storage effect was more obvious.The binary microcapsule phase change thermal storage materials have polyurethane structure,and the functional groups of PEG 800 and PEG 1000 are not damaged during the preparation process.The microcapsule matrix structure can form stable chemical bond with the core material,which reduces the displacement of phase transition temperature to low temperature.The binary heat storage mode reduces the supercooling of PCM.（3）Based on the porous PCM,the porous phase change thermal storage wood plastic composites（TSWPC）with high thermal storage density and good thermal stability was prepared by extrusion molding.When the content of porous PCMs was 40%,porous TSWPC represented high thermal storage values which were 117.83 J·g^-1 and 116.80 J·g^-1 during solidifying-melting cycle,and the thermal stability was good.The internal heat conduction of porous TSWPC depends on the molecular chain vibration of polymer matrix and the interaction between lattice phonon and filler lattice phonon in the form of diffusion.Porous phase change thermal storage wood plastic composite had limited ability to regulate indoor temperature within 24 hours,and only played the effect of thermal storage and temperature regulation within its own phase change temperature range.（4）Based on the binary microcapsule PCM,the microencapsulated TSWPC with excellent thermal storage performance was prepared by the mixing molding method.When the content of microencapsulated PCM was 40%,the thermal storage values of the microencapsulated TSWPC during the solidifying-melting cycle were 127.14 J·g^-1 and 121.37 J·g^-1.Under the influence of binary energy storage mode,during the process of crystallizing and melting,the width of phase change temperature ranges of the microencapsulated TSWPC were 23.37℃and 20.64℃,respectively.The bridging between microcapsules and WPC enhanced the interface effect of microencapsulated TSWPC.In the process of heat transfer,the heat transfer depends on the molecular chain vibration of polymer matrix,the interaction of lattice phonon and packing lattice phonon in the form of diffusion.The microencapsulated phase-change thermal wood plastic composite can adjust the indoor temperature within 24 hours,which slows down the change of indoor temperature.