Preparation And Solar-thermal Properties Of Polyurethane Based Solid-solid Composite Phase Change Materials

Thermal utilization technology of solar energy is the most direct and efficient one among ways of solar utilization.However,due to the discontinuity,the solar energy usage is of low efficiency.To solve this problem,some researchers focus on the development of new storage media materials of solar heat,some keeping working on adding various additives to reach high thermal conductivity,the others tries on increasing the coating rate of phase change material to improve the thermal storage performance.Besides,the study about improving the absorption performance of sunlight from full spectrum is rarely reported.Therefore,a new multifunctional composite solid-solid phase change material was prepared by selecting solid-solid phase change material polyurethane(PU)as the matrix and copper sulfide(Cu S)nanometer material as the additive,which not only improves the heat transfer and heat storage performance,but also improves the heat absorption performance,so as to improve the solar energy utilization efficiency.For photo-thermal conversion materials,copper sulfide nanomaterials prepared in different solvent environments were explored,so as to optimize the preparation scheme of composite materials with excellent performance in yield,solar thermal conversion and absorption capacity,thermal stability and particle dispersion.Results showed that the copper sulfide monodisperse nanodisks synthesized through ethylene glycol based solvothermal method showed admirable light absorption efficiency in full spectrum,good dispersibility,relatively high yield and reliable thermal stability.Besides,low temperature and short time required for the preparation of the copper sulfide nanodisks made it a kind of solar-thermal conversion material with great market potential.What's more,the suitable synthesis scheme and good properties of the copper sulfide nanomaterials are surely leading to a bright prospect for application in solar-thermal conversion functional composite materials.Based on the copper sulfide nanomaterials prepared in the earlier stage,a new multifunctional composite phase change material was prepared by using polyurethane solid-solid phase change material.The monodisperse copper sulfide nanodisk was firstly prepared by solvothermal method,and then the uniform composite of copper sulfide nanodisk and polyurethane phase change substrate was realized in the in-situ polymerization process.Compared with pure polyurethane phase change materials(phase change enthalpy 140 J/g),composite materials with 4 wt% Cu S nanodisks had a higher energy storage density although their enthalpy value was reduced to 120 J/g.In addition,the experimentally prepared Cu S@PU composite phase change materials exhibited excellent shape stability,thermal stability and cyclic stability,which was attributed to the solid-solid phase change properties of the polyurethane material itself.The composite materials were also indicated to be quite reliable that there was only 0.6% energy loss after 100 cycles of heating and cooling.The full-solar spectral response capability of copper sulfide nanocrystals makes the solar-thermal conversion efficiency of Cu S@PU composite phase change materials(up to 91%)higher than that of most reported ones.Moreover,the new composite phase change material Cu S@PU integrated heat absorption,heat transfer and heat storage functions,and realized the three processes of solar energy absorption,conduction and storage into one,thus greatly improving the efficiency of solar-thermal conversion system.High energy storage density,appropriate phase transition temperature,excellent thermal stability and high solar-thermal conversion efficiency made this new multi-function phase change material Cu S@PU had potential application in utilization of solar energy systems in the future.