Preparation And Property Of ATO-Based Transparent And Heat Insulating Coatings And Films

Most space that human lives in (such as housing and cars) require possessing two main functions: energy saving and daylight utilizing. General glass can hardly insulate the infrared radiation thus brings enormous energy loss. Currently existing Low-E glass could not obtain popular application due to its high production cost and poor performance on some aspects. With high transparency in visible light and satisfying infrared-insulating performance, antimony doped tin oxide (ATO) nanoparticles are an ideal transparent and heat-insulating material. The preparation of ATO based novel coat can solve the problem of transparent and heat-insulating simultaneously. In addition, ATO based coat has other advantages such as low cost and simpler production process. It has high practical values and wide market prospects.In this paper, the dispersing performance of ATO in aqueous medium was studied firstly. The influence of dispersing methods, type and content of dispersants, pH value adjusting, dispersing time and further treatment after dispersing on the ATO slurry stability and dispersibility were discussed. The results indicate that when the dispersant was KH570 (with 1% of the weight of ATO) and the pH value of the final slurry was adjusted to～8, the dispersion stability is best; Ball-milling dispersion is more effective than ultrasonic dispersion. It is important for adjusting pH value of the dispersion system to～9 before milling. The pollutants in ATO slurry can be removed by method of centrifugal sedimentation, forming stably dispersed ATO slurry with average diameter～70 nm.Transparent and heat insulating coat with high performance is prepared by mixing aqueous polyurethane film-forming agent (WPU) with ATO aqueous nano slurry. The coatings’ heat-insulating effect was measured by long time tracking the temperature changes not only in polystyrene foam boxes covered by ATO/PU coated glass plate and PU coated glass plate but also on the plate surfaces all under infrared light lamps. The results showed that the temperatures in ATO/PU glass covered box were always lower than those in PU glass covered box (～8℃), while the temperatures on ATO/PU glass surface were always higher than those on PU glass plate surface (～17℃). However, all the temperatures approached balance after certain irradiation time. These results demonstrate the heat-insulating effect of ATO/PU coatings is attributed to their absorbing to infrared light but not reflecting and the heat-insulating effect is durable and stable. The spectrum performance characterized by ultraviolet-visible light-infrared spectrophotometer further confirms that the visible light transmittance is up to 65% and infrared radiation insulation is over 85%; TEM imaging confirmed the ATO nanoparticles were dispersed well in PU film (with diameter all≤100 nm).Based on the study of transparent and heat insulating ATO/PU coating, ATO/PU composited films were prepared by casting dispersed nano-ATO/ PU suspensions on poly (dimethylsiloxane) (PDMS) templates replicated from fresh lotus leaves. Surface temperature changes under an infrared light lamp and water contact angle measurements demonstrated ATO introduction not only endowed films thermal insulation function but also ensured films surface superhydrophobicity (water contact angle up to 151.3±2.1°), the reason for surface superhydrophobicity was studied by scanning electronic microphotography (SEM) imaging coupled with Energy-Dispersive X-ray spectroscopic (EDX) measurements.In the end, the mechanism of heat insulation was studied by analyzing the light energy flow diagram and referring semiconductor physics relative theory. It showed that the obstructing of ATO nanoparticle to the incident light energy mainly derived from absorbing most part of photons and reflecting a small part of photons.