Study On Transparent And Heat Insulating Coatings Prepared From Nanometered Indium Tin Oxide (ITO)

As the society pays more and more attention to problems of energy sources and environments, higher and higher requirements have been put forward to the transparent and heat insulating performance of the glass. Though the transparency of the ordinary glass is considerably high, it can hardly insulate the infrared radiation, which results in enormous energy lost for occasions needing to be insulated from heat radiation. The existing heat insulation glass has the defects on the performance or cost generally. Having high transparency in visible light and effective infrared-insulating performance, nano-metered indium tin oxide (ITO) is an ideal transparent and heat-insulating material. The preparation of transparent and heat insulating coating made from nano-ITO can solve these problems. In addition, it has the advantages of simple process and low cost. So this kind of coating has extremely high practical application value and wide market prospects.The dispersion behaviors of nano-ITO in aqueous system are studied in this paper firstly. Influence of PH value, type and content of dispersants, dispersion medium, processing parameters, and different dispersing methods on the dispersion stability is discussed. The results indicated that the isoelectric point determined in water was 7-8. The dispersion stability is improved when PH value is above or below this value. The optimum dispersant and it's content in dispersion system is DP-512 and 10% of the weight of nano particles. The maximum improves of dispersion stability are acquired when 37% of ethanol by volume is added to the dispersion system. Influence of different dispersing methods and processing parameters on the dispersion stability are compared. Ultrasonic dispersion method is more effective than milling and high-speed dispersion methods. The combination of both milling and ultrasonic dispersion methods can improve the dispersing effects slightly than ultrasonic dispersion, which can acquire a nano ITO slurry having mean diameter of 200nm and a narrow particle size distribution.High performance transparent and heat insulating coating is prepared by addingsilicone film-forming agent to ethanol slurry of nano ITO and adjusting cosolvent and PH value of the coating system. Through the results of coating's mechanics, optical performance and SEM analysis, we can draw a conclusion that the CPVC value of the coating is near to 0.34. Coatings having good comprehensive mechanics performance are prepared by adding a protecting layer of hydroxyl acrylic resin on the heat insulating layer. The coating has remarkable solar spectrum selectivity which can transmit visible light and insulate infrared radiation. For the coating which has a PVC value of 0.34, the visible light transmittance is 83.01% and the solar direct transmittance is 63.35% and 66.71% respectively when the atmosphere quality is 1 and 2. That is to say, 36.65% and 33.29% of the heat of solar radiation is insulated respectively. SEM analysis of the coatings indicate that the particle size of ITO in coatings is less than 50nm. The heat insulating effects of coatings is determined under an self-made equipment. Results indicate that the coating has obvious heat insulating effects, which has a temperature difference of above 10#-more than 20# at most-between the heat insulating and ordinary glass under iodine-tungsten lamp.