Preparation And Properties Of Vanadium Dioxide Based Water-based Intelligent Heat Insulation Coatings

The increased indoor temperature caused by infrared rays in the Sun penetrating glass windows will increase the use of air conditioning,resulting in a large amount of energy consumption.As a typical thermochromic material,vanadium dioxide（VO₂）can undergo a reversible phase transition at 68℃.The intelligent control of the transmittance of infrared rays on the glass surface can be realized by employing the difference in infrared reflectance before and after the phase transition of VO₂.Therefore,the preparation of VO₂-based water-borne intelligent heat insulation coating and its application on building glass can reduce the indoor temperature rising for energy saving and CO₂emission reduction.However,the poor stability and inferior compatibility between an organic resin and inorganic VO₂powders limit practical application.To solve the above problems,the strategy via designing and constructing a core-shell structure was used to achieve the surface modification of VO₂powders.The stability and dispersion of VO₂in aqueous system could be improved significantly.Furthermore,the excellent solar modulation capability of the coating is simultaneously increased from 8.47%to 10.84%.The main results of the study are summarized as below:1.Monoclinic vanadium dioxide（VO₂（M））nanoparticles were prepared by a hydrothermal one-step method.The particle size of VO₂（M）is 40 nm and the phase transition temperature is 61.3℃by adjusting the reaction time,temperature,and other parameters.Subsequently,the surface modification of VO₂（M）was carried out by using 3-（trimethoxy-silica-methyl）propyl methacrylate（KH-570）,and VO₂@KH-570 hybrid particles were successfully prepared.The shell materials can not only improve the stability of VO₂（M）but also successfully introduce the double bond functional groups to the particle surface,endowing it with reactivity.The mercapto-terminated hydrophilic poly（N,N-dimethylacrylamide）（PDMA）homopolymer was prepared by Reversible Addition-Fragmentation Chain Transfer（RAFT）Polymerization and ammonolysis reaction.Finally,PDMA is grafted onto the surface of VO₂by"Grafting to"method to obtain the VO₂@PDMA hybrid nanoparticles.The dispersibility and stability of the modified VO2nanoparticles in a water-based system are significantly improved,and the solar modulation capability of the intelligent thermal insulation coating prepared by VO₂@PDMA and polyvinylpyrrolidone（PVP）is also improved from 8.47%to 9.58%,compared with the unmodified VO₂powder.2.The stability of VO₂powder was further improved by preparing amphiphilic block polymerpoly（hexafluorobutylmethacrylate-b-N,N-dimethylacrylamide）（PDMA-b-PHFBMA）as a double-shell material.The internal PHFBMA fluoropolymer shell has shown excellent hydrophobicity and weatherability,which can greatly improve the stability of VO₂in the reported system.The external PDMA hydrophilic chain segment can improve the dispersion of VO₂powder in aqueous system.The results show that the dispersibility,acidity resistance,and oxidation resistance of VO₂@PHFBMA-b-PDMA powder in the aqueous phase are significantly improved.The VO₂@PHFBMA-b-PDMA/PVP thermal insulation coating has a solar modulation capability(ΔT_sol)upto 10.85%.3.VO₂@PHFBMA-b-PDMA particles with excellent performance were selected based on the sunlight modulation ability of VO₂@PHFBMA-b-PDMA/PVP thermal insulation coating.The VO₂-based water-borne intelligent heat insulation coating was prepared by using commercial water-borne resin instead of PVP.The intelligent heat insulation coating can be prepared by a simple coating process.The heat insulation glass coating has shown excellent visible light transmittance,with robust adhesion and hardness.The properties of UV resistance and temperature resistance of the coating meet the requirement of the state national standard（GB/T 29501-2013）.The coating can quickly respond to the changes in ambient temperature without external energy equipment,realizing intelligent indoor temperature control.Meanwhile,the heat insulation property of the glass can be designed based on the thickness（3-10μm）of the 4-14℃coating.And through the roll coating or spray coating process applied in new glass and old window transformation,to achieve large-scale production and use.