Preparation And Properties Of Near-infrared Colorful Thermal Insulation Coating

With environmental protection and energy saving,and low-carbon emission reduction have increasingly become the mainstream of society,and various corresponding studies have also emerged.The high temperature in summer will cause a serious urban heat island effect in the city.In order to reduce the impact of the urban heat island effect,colorful thermal insulation coatings have been paid attention as a simple and quick solution.In this subject,colorful thermal insulation coatings are studied from two aspects:resin and powder.Water-based polyurethane（WPU）is a resin with environmental protection and good physical and chemical properties.It can be modified with silicone to improve its hydrophobicity and water resistance to adapt to the outdoor working environment.Fe and Fe/Al are doped into La YO₃ and Y₂Ce₂O₇rare earth metal oxides to prepare colorful inorganic pigments with high reflectivity in the near-infrared region.The resin and pigments are compounded to obtain colorful insulation coating with high near-infrared reflectivity,and the actual thermal insulation effect of the coating was investigated.The main research contents of this paper are as follows:Firstly:the preparation and performance study of ethoxysilane modified waterborne polyurethane,by introducing siloxane segments to improve the basic performance and water resistance of waterborne polyurethane coatings.Firstly,use 3-isocyanatopropyltriethoxysilane（IPTS）and diethanolamine（DEA）to make a homemade diol（Si-2OH）containing ethoxysilane side chain,and then use isophorone diisocyanate（IPDI）,polycarbonate diol（PCDL）,dimethylolpropionic acid（DMPA）,self-made silicon-containing diol（Si-2OH）,pentaerythritol triacrylate（PETA）and trimethylolpropane（TMP）as the main raw material to synthesize UV curable waterborne polyurethane containing ethoxysilane in the side chain.The structure of UV-WPU and the performance of the coating film were characterized and tested by infrared（FT-IR）,nuclear magnetic（¹H NMR）,optical contact angle measuring instrument,ultraviolet spectrophotometer,and thermogravimetric analyzer,and at the same time,explore the influence of the self-made Si-2OH addition on the properties of polyurethane and its coating film.The results showed that the introduction of Si-2OH increased the optical contact angle of the waterborne polyurethane coating from 65.6°to 88.2°,and the transmittance decreased to a certain extent,but the impact did not exceed 1%,thermal stability,adhesion and pencil strength have been improved to a certain extent,and its storage stability exceeds 180 days.When the molar ratio of Si-2OH is 10%,its tensile strength can reach 5.89 MPa,but the elongation at break will decrease to a certain extent.Through the comparison of various data,when the addition amount of Si-2OH is selected as 10%,the organic silicon-modified UV-curable waterborne polyurethane（UV-WPU-Si-10）has the best overall performance.Secondly:preparation of La_1-xFe_xYO₃ and La_1-xFe_0.5xAl_0.5xYO₃near-infrared colorful thermal insulation powders and their corresponding colorful thermal insulation coatings.Using hydrothermal method,using Y（NO₃）₃·6H₂O,La（NO₃）₃·6H₂O,Fe（NO₃）₃·9H₂O and Al（NO₃）₃·9H₂O as raw materials,a series of Fe doped and Fe/Al doped La YO₃powders were prepared.The above powders are used as the colorful functional fillers and resins compound to prepare the near-infrared colorful thermal insulation coating.XRD was used to characterize the composition of the powder,the spectrophotometer was used to characterize the color of the powder,and the color change of the powder after soaking in the acid solution was measured to characterize its acid resistance,the thermogravimetric analyzer was used to characterize the heat resistance of powder.Measure the spectral reflectance of the powder and coating with an ultraviolet-visible-near-infrared spectrophotometer,and calculate the near-infrared reflectance,visible light reflectance and sunlight full-band reflectance.The effects of Fe and Fe/Al doping on the color,acid and heat resistance and near-infrared reflectivity of the powder and the corresponding coating were explored.The results show that as the single doping amount of Fe increases,the color of the powder changes from white to yellow to orange,and the near-infrared reflectivity of the powder and the corresponding coating gradually decreases.When the doping amount is 0.7,The near-infrared reflectivity of the powder and the corresponding coating are64.04%and 52.74%,respectively.When the doping amount is 0.1,the reflectivity values are82.31%and 65.5%,respectively.When Fe/Al doped,the color change of the powder changes from white to yellow,and the near-infrared reflectivity of the powder and the corresponding coating also gradually decreases but the trend is slow.When the doping amount is 0.1,the near-infrared reflectivity of the powder and the corresponding coating are 89.31%and 71.81%,respectively.When the doping amount is 0.7,the reflectivity values are 80.32%and 63.37%,respectively.Both Fe and Fe/Al doped powders have good acid and heat resistance.Through the testing,it is found that when the powder and resin are compounded,the overall performance of the coating is best when the solid content of the powder is 20%.Therefore,coatings with 20%solid content were prepared for testing in the subsequent tests.In the actual thermal insulation effect test,the stable temperature of the corresponding coatings of each powder after heating up can reach up to 13.7℃compared with the control group.Thirdly:the preparation of Y₂Ce_2-xFe_xO₇and Y₂Ce_2-xFe_0.5x Al_0.5xO₇ near-infrared colorful thermal insulation powders and their corresponding colorful heat-insulating coatings.Using Y（NO₃）₃·6H₂O,Ce（NO₃）₃·6H₂O,Fe（NO₃）₃·9H₂O and Al（NO₃）₃·9H₂O as raw materials,a series of Fe doped and Fe/Al doped Y₂Ce₂O₇ powders were prepared by the sol-gel method.The resin selected in the above powder first system is compounded to prepare a near-infrared color thermal insulation coating.The above powders are used as the colorful functional fillers and resins compound to prepare the near-infrared colorful thermal insulation coating.XRD was used to characterize the composition of the powder,the spectrophotometer was used to characterize the color of the powder,and the color change of the powder after soaking in the acid solution was measured to characterize its acid resistance,the thermogravimetric analyzer was used to characterize the heat resistance of powder.Measure the spectral reflectance of the powder and coating with an ultraviolet-visible-near-infrared spectrophotometer,and calculate the near-infrared reflectance,visible light reflectance and sunlight full-band reflectance.The effects of Fe and Fe/Al doping on the color,acid and heat resistance and near-infrared reflectivity of the powder and the corresponding coating were explored.The results show that:The doping of Fe（doping amount does not exceed 0.3）and Fe/Al（doping amount does not exceed 0.5）is well incorporated into the crystal lattice of Y₂Ce₂O₇ without causing the formation of other impurity phases,the doping of Fe and Fe/Al reduces the lightness of the pigment,the color is more yellow and red,and the saturation also increases.The overall color of the pigment changes from yellow to orange.Both Y₂Ce_2-xFe_xO₇ and Y₂Ce_2-xFe_0.5xAl_0.5xO₇series powders have good acid resistance and heat resistance and excellent near-infrared reflectivity.The near-infrared reflectance of Y₂Ce_2-xFe_xO₇ series powders are all above 70%,and the near-infrared reflectance of Y₂Ce_2-xFe_0.5xAl_0.5xO₇ series powders are all above 82%.Among them,the lowest near-infrared reflectance is 71.76%of Y₂Ce_1.7Fe_0.3O₇,and the highest is 88.89%of Y₂Ce_1.95Fe_0.025Al_0.025O₇.The near-infrared reflectance of Y₂Ce_2-xFe_xO₇series coatings are all above 56%,and the near-infrared reflectivity of Y₂Ce_2-xFe_0.5xAl_0.5xO₇ series coatings are all above 68%,except for the Y₂Ce_1.7Fe_0.3O₇ powder,the corresponding coating temperature difference is 7.5℃,the temperature difference of other coatings corresponding to the pigments is above 10℃,the highest of is 14.3℃of the coating corresponding to Y₂Ce_1.95Fe_0.025Al_0.025O₇ powder（except the coating corresponding to Y₂Ce₂O₇powder）.