Study On The Design,preparation And Structure-function Relationship Of PEG Phase Change Materials Regulated By Graphene

Phase change materials(PCMs)is one of the most important part of the new energy materials.As an advanced energy saving material,the phase change material can store and release latent heat when it undergo phase change process.Phase change materials not only improve the storage of intermittent and unstable energy to solve the problem of the mismatch between supply and demand of energy usage in time and space,but also can be used as controlled thermal storage candidates for thermal management of solar energy,wind energy,geothermal energy and industrial waste heat etc.PCMs can increase the energy utilization efficiency and be significant to relieve the pressure of environment and energy.Polyethylene glycol(PEG)is an important branch in the field of new organic PCMs,it dispalys phase change temperature closed to the body temperature,large heat of melting and corrosion resistance.According to the different molecular weight design,PEG phase transition temperature can be adjusted and used in low temperature.However,there are some difficulties in using PEG for latent heat storage like low thermal conductivity,ease of leakage with solid-liquid phase transition and low thermal stability,which are remarkable obstacles in the practical application of PEG for energy storage.In this paper,we used Hummers to prepare graphene oxide(GO),a phase change material consisting of three-dimensional(3D)graphene aerogel(GA)composite PEG was prepared by a convenient one-step hydrothermal method,two-dimensional graphene sheets modified chemically can be intergrated into3 D macroporous structures via Vc hydrothermal reduction technologies and formed graphene-based gels.The structure of 3D graphene-based architecture not only provides heat conduction channel for PEG heat transfer,but also provides sufficient adsorption space matrix to solve the leakage of PEG.With the increasing of the reduction degree,GO layer defect is reduced than pristine GO,the thermal physical and chemical properties are similar to graphene.Compared with PEG,the loss rate of 3D graphene PEG gel composited PCM enthalpy was less than 1%,the thermal conductivity increased by 61.7%,PEGcontent reached up to 99.3%.The material leakage phenomenon did not occur in the liquid at 70℃ after 30 min.When reduction degree was maximum,thermal stability increased by 20℃ compared with the pure PEG.In addition,because the surface of GO oxygen contained functional group and PEG molecular could be designed,functional PEG PCMs prepared by chemical method.In this paper,acylating chlorination,which make the GO has high chemical reactivity,occurred on the surface of the GO,due to reduced oxygen containing functional groups reduced GO defects,increased both the GO of chemical activity and reduction.Small organic molecules acylation chloride trimer,who are sensitive to temperature,are selected to modified acylation with GO chloride.Graphene inorganic organic functional carrier is prepared,when the carrier is completely aminated,amino modified active site provides support of PEG,PEG was modified by 4-4’-two diphenylmethane isocyanate to make the PEG terminate with reactive cyanate.Functionalized graphene PEG composite carrier phase change material was prepared by the aggregation of amino acid and reactive cyanate.The loss rate of enthalpy for material is 5.3%,the thermal conductivity increased by 69.5%,thermal decomposition temperature increased by 50℃,there is no leakage occurred in 70℃,90℃ and 110℃,respectively in30 min.Graphene PEG gel composite phase change and functionalized graphene PEG composite PCMs successfully prepared which present high thermal conductivity,leakage resistance and thermal stability of integration.