| Low-carbon economy becomes a global focus, and energy-saving materials are welcomed greatly. It is significant to prepare new transparent heat-insulating coating for energy saving by using ultraviolet and infrared shielding properties of inorganic particles. With high transparency in visible light and excellent infrared-shielding performance, nano antimony doped tin oxide (ATO) is used to prepare heat-insulating coating. At present, nano-ATO heat-insulating coating is prepared mainly by mixing the waterborne nano-ATO slurry and polymer emulsion directly, which has a defect that nano-ATO particles can not be dispersed into polymer matrix well, which depress the heat-insulating ability. In this work, nano-ATO/organic monomer dispersion and waterborne nano-ATO slurry were prepared by surface modification and dispersion in organic monomer and water medium, respectively. Poly(MMA-BA)/nano-ATO composite emulsion is prepared through in-situ conventional emulsion polymerization and miniemulsion polymerization, respectively. Subsequently, the transparent heat-insulating coating with excellent heat-insulating property was prepared. The main research contents and achievements are listed as following:Firstly, nano-ATO dispersion with good stability was prepared in the medium of MMA/BA or water, and nano-ATO particles were dispersed well. The influence of modifier type and amount, dispersing condition on the stability of nano-ATO dispersion were studied. Nano-ATO dispersion was characterized by using TEM, FTIR, laser particle diameter analyzer and TG, the modification mechanism of nano-ATO particles with KH570 in monomer medium was discussed. It is found that the stability of nano-ATO dispersion is affected greatly by the modifier KH570. In monomer medium, nano-ATO particles are modificated mainly through self-condensation of KH570 on the surface of nano-ATO particles. The stability of nano-ATO/organic monomer dispersion can be improved when modification time, ultrasonic dispersion time and ultrasonic output power is increased. The optimal preparation condition of nano-ATO/organic monomer dispersion is: the amount of ATO is 3%, the amount of KH570 is 15%, modification time is 24 hour, ultrasonic output power is 360W, and dispersion time is 12 minutes. Under the optimal preparation condition, the average particle size of modified ATO particles in organic monomer dispersion is 70 nm. The stability of waterborne nano-ATO slurry is affected by dispersing method, dispersant dosage, pH values and viscosity. The optimal preparation condition of waterborne nano-ATO slurry is: the combined dispersing methods of high-speed shearing, bead milling and ultrasonication is used, the amount of ATO is 2%, the amount of KH570 is 1.5%, the amount of dispersant 3275 is 0.2%, pH value is 7, and viscosity is 88mPa.s. Under the optimal preparation condition, the average particle size of modified ATO particles in water dispersion is 94 nm.Secondly, poly(MMA-BA)/nano-ATO composite emulsion was prepared through in-situ conventional emulsion polymerization with main monomer MMA/BA and compound emulsifier of SDS and OP-10. Influence of monomer, emulsifier, emulsification condition, nano-ATO amount, initiator, polymerization temperature on encapsulation efficiency, coagulation ratio, monomer conversion, morphology and diameter distribution of latex particles were studied. The latices and its films were characterized by using TEM, laser particle diameter analyzer, TG and DSC. It is found that nano-ATO particles are encapsulated in the latex particles. With the increasing of nano-ATO amount, the encapsulation efficiency decreases. Functional monomer AA can both improve encapsulation efficiency and also reduce coagulation ratio. The optimal polymerization condition is: the amount of emulsifier (SDS/OP-10=2:1) is 4%, stirring speed is 400 r/min, ultrasonication time is 10 min, the amount of AA is 3%, MMA/BA ratio is 6:4, nano-ATO amount is 3%, the amount of KPS is 1.0%, polymerization temperature is 75℃. Under the optimal preparation condition, the average particle size of the latex is 77 nm, the polydispersity is 0.277, the encapsulation efficiency is 56.6%, the coagulation ratio is 7.9%, and monomer conversion is 90.4%.Thirdly, poly(MMA-BA)/nano-ATO composite miniemulsion was prepared by miniemulsion polymerization with SDS as emulsifier and HD as costabilizer. Influence of monomer, emulsifier, costablizer, ultrasonic time, nano-ATO amount, initiator, polymerization temperature on encapsulation efficiency, coagulation ratio, monomer conversion, morphology and diameter distribution of latex particles were studied. The latices and its films were characterized by using TEM, laser particle diameter analyzer, TG and DSC. It is found that miniemulsion polymerization has higher encapsulation efficiency, lower coagulation ratio, larger average particle size and narrower diameter distribution than conventional emulsion polymerization when nano-ATO amount is the same. It can both improve encapsulation efficiency and polymerization stability by adding costabilier into oil phase directly. With the increasing of amount of HD, the encapsulation efficiency increases, while the coagulation ratio decreases. However, when the amount of HD exceeds 4%, the encapsulation efficiency and the coagulation ratio remains stable. The optimal polymerization condition is: MMA/BA ratio is 6:4, the amount of SDS is 4%, ultrasonication time is 10min, the amount of costablizer is 4%, nano-ATO amount is 3%, the amount of KPS is 1.0%, polymerization temperature is 80℃. Under the optimal preparation condition, the average particle size of the latex is 84 nm, the polydispersity is 0.107, the encapsulation efficiency is 78.0%, the coagulation ratio is 3.1%, and monomer conversion is 90.8%.Finally, waterborn nano-ATO transparent heat-insulating coating was prepared by adding film-forming agent, thickening agent and pH adjusting agent into the composite latex prepared by in-situ emulsion polymerization or miniemulsion polymerization. The influence of nano-ATO amount on the heat-insulating property, water absorption and mechanical properties were studied. The heat-insulating property was characterized by using UV-VIS-NIR spectrophotometer and heat-insulating ability testing equipment, the infrared shielding mechanism of nano-ATO was discussed. It is found that the heat-insulating ability can be improved with the increasing of the content of nano-ATO in composite film. The infrared shielding property of nano-ATO is due mainly to the absorption. The heat-insulating coating prepared by composite miniemulsion has better heat-insulating ability than that prepared by composite emulsion, its shading coefficients decrease from 0.89 to 0.82 and visible light transmittance is 79.6%. The indoor temperature of testing equipment with heat-insulating coating is 5.8℃lower than that of testing equipment with the control sample. At same time, nano-ATO can improve the water resistance, impact strength and the pendulum hardness of composite film.
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