Study On Preparation And Thermal Properties Of Shape-stabilized Sodium Acetate Trihydrate Composite Phase Change Materials

Phase change thermal storage materials have many advantages,such as high heat storage capacity,stable temperature and recyclable,and have broad application prospects in some aspects.Such as controling the ambient temperature to maintain a constant temperature,building energy conservation and heat preservation,recycling the thermal energy and electric energy flat valley peak shaving,so that they have attracted much attention.The shape-stabilized phase change thermal storage materials are prepared by complexing the phase change materials with the others packaging materials to solve the following problems:leakage and large volume change,them also could improve thermal stability,so that it could be used in environmental temperature management systems.So far,organic phase change materials be used more in environmental temperature management systems,because of the poor compatibility between inorganic phase change materials and organic packaging materials.But relatively,inorganic phase change materials have commonly phase transition temperature,lower cost and higher heat storage capacity.In this thesis,complex the the sodium acetate trihydrate（SAT）with different support materials to prepare several kinds of shape-stabilized phase change thermal storage materials,prepared a new phase change silicone potting glue,and improved the thermal physical properties on the whole,has a positive effect on promoting the inorganic phase change materials to be used in battery,precision instruments and aviation’s ambient temperature thermal management systems.SAT was selected as the inorganic phase change material.In this thesis,use the melt-mixing method or porous adsorption method to prepare the shape-stabilized phase change materials,and use a series of test instruments to characterize the thermal physical properties of the samples,at the same time analysis how the preparation conditions to affect the samples’thermal physical properties,and get the best formula.The research contents and mian results are as follows:（1）Use two surfactants,such as TX-100（TX）and cetyl trimethyl ammonium bromide（CTAB）to modifiy the expanded graphite（EG）:the unmodified EG′s contact angle is about 77.0°,When use the unmodified EG to adsorb the melted SAT,need 9 wt%EG and 5 h to reach the non-leakage target,at this time,the latent heat is 185.7 J/g and the thermal conductivity is 2.112 W·m^-1·K^-1;In this thesis,named the EG modified by the TX-100 as TX-EG,its contact angle is 16.3°,When use the TX-EG to adsorb the melted SAT,need 8.5 wt%TX-EG and 3 h to reach the non-leakage target,at this time,the latent heat is 212.4 J/g and the thermal conductivity is 2.097 W·m^-1·K^-1;In this thesis,named the EG modified by the CTAB as CTAB-EG,its contact angle is 10.3°,when use the CTAB-EG to adsorb the SAT,need 7.5 wt%CTAB-EG and 1 h to reach the non-leakage target,at this time,the latent heat is 205.7 J/g and the thermal conductivity is 2.005W·m^-1·K^-1.After modified by two kinds of surfactants,the thermal conductivity changes little,but the adsorption capacity and adsorption rate of melted SAT obviously improved,reduced the cost,improved the latent heat.That is because of the surfactants increased hydrophilic functional groups,so that improved the hydrophilic,increased adsorption capacity of melted SAT,increased the latent heat.（2）In this thesis,use the carboxymethyl cellulose（CMC）and xanthan gum（XG）as modified materials to complex with melted SAT,so that to prepare the shape-stabilized phase change materials.Through experiments,it can be concluded that when the mass ratio of CMC is 4 wt%,the shape-stabilized phase change materials can be formed,at this time,the latent heat is 222.0 J/g,and the thermal conductivity is 0.5849 W·m^-1·K^-1.When the mass ratio of XG is 6 wt%,the shape-stabilized phase change materials can be formed,at this time,the latent heat is 215.8 J/g,and the thermal conductivity is 0.5785 W·m^-1·K^-1.It can be seen that CMC and XG can make the SAT shape-stabilized and maintain a high heat storage capacity.CMC has better modification effect than XG,it can make the SAT shape-stabilized with smaller mass ratio,maintains a larger heat storage capacity,reduces the influence of thermal conductivity.That is because of the XG is extremely hydrophilic,when add it to water,it absorbs water quickly and expands into a gelatinous substance,the high speed causes the outer layer to expand completely,cause the water molecules are no longer able to enter the inner layer,so that the use of XG must be more to achieve the same effect as CMC.（3）Using the CMC to melting with the silicone potting glue,and then modifiy the SAT so that could get shape-stabilized phase change materials.Through the experiments could found that,this way could reduce the cure time from 72 h to 2 h;The mass ratio of silicone potting glue could be reduced from 15 wt%to 10 wt%,at this time,the latent heat of the product is 191.7 J/g;After 50th cycles,the latent heat decreased 8.7%,before modification,the latent heat decreased 20.3%,so that the thermal stability was obviously improved.This new phase change heat storage sealant has a faster solidification rate and higher latent heat,It is expected to be applied to the thermal management system of power battery,to achieve the long-term adjustment of the battery operating environment temperature.