Transparent self-cleaning coating preparation process

China Coatings Online News Information
Abstract: With butyl titanate and ethyl silica as the foreboding, nanoTiO2/SiO2 composite film with photocatalytic activity was prepared at low temperature using sol-gel method, and the effect of test temperature, pH, coating number, stirring speed and other factors on the hydromassive properties of the coating was investigated. The results showed that the contact angle of the TiO2/SiO2 composite film, which had a test temperature of 5 degrees C, a pH of 2.5, a TiO2 mass score of 50%, a coating layer of 3 layers and a speed of 1500r/min, was at a minimum of 6.8 degrees. Through photo-catalysis and outdoor testing, it is shown that homemade self-cleaning coatings have good photo-catalytic effect and anti-fouling properties.
key words: photo-catalysis; self-cleaning; hydromassive; anti-fouling; Paint
In-figure classification number: TQ630.6 Document identification code: A article number: 1006-2556 (2012) 02-0049-04
0. foreword
notTiO2, because of its high activity, good stability, non-toxic, low price and other advantages, is currently the most widely used photocatalytic materials, and has been successfully applied in many fields, such as sanitary ware, optical instruments, coatings, glass, highway walls, etc. The addition of SiO2 in nanoTiO2/SiO2 composite film makes TiO2/SiO2 composite film not only maintain the photocatalytic activity of nanoTiO2, but also effectively improve the ultra-hydromassive effect of the film, mainly because SiO2 materials tend to form thicker physical adsorption on the surface. The water layer, so that the film surface shows hydro-hydrogenic properties, and can prevent the adsorption of oxygen in the air on the film surface, so that the chemical adsorption of water to oxygen replacement slows down, thus prolonging the duration of its ultra-hydro-hydrogenicity, so that the film can still maintain a longer period of hydro-hydrogenicity after stopping lighting. Domestic research on SiO2 doping nanoTiO2 reported more, but the thin-film products are less, and basically after 450 to 500 degrees C high temperature treatment, so that nanoTiO2 film has photocatalytic activity, which makes the application of nanoTiO2 with photocatalytic activity has been greatly limited. In this paper, a relatively simple method is used to synthesize nanoTiO2/SiO2 composite sol with photocatalytic activity, and after low temperature filming, nanoTiO2/SiO2 composite has good photocatalytic activity. The hydroffinity of the film surface is combined with its photo catalytic activity, which makes the film surface self-cleaning and easy to clean. And through photo catalytic test and outdoor test, it is shown that homemade self-cleaning coating has good anti-fouling properties.
1. Test part
1.1 test raw materials
butyl titanate, chemical purity, Shanghai Kefeng chemical reagents; positive silicate, chemical purity, Beijing chemical plant; waterless ethanol, hydrochloric acid, analysis pure, Yantai City double chemical; acetyl acetone, analytical pure, Tianjin Guangfu Fine Chemical Research Institute; distilled water, homemade.
1.2 Test Instrument
Fourier Infrared Chromatography, TENSOR, Bruker Spectroscopic Instrument Co., D.C.; Contact Angle Assay, HARKE-SPCA, Beijing Harco Test Instrument Factory; Straight Tube Quartz Ultraviolet Sterilization Lamp, Lianyungang Donghai County Innovation Light Plant; Full-intelligent light transmission meter, MN-TTA, Tianjin Qili Technology Co., Ltd.; high-speed dispersion machine, GFJ-0.4, Shanghai Modern Environmental Engineering Co., Ltd.; Distilled water generator, DZF-6050, Beijing Medical Equipment Factory.
1.3 test process
1.3.1 preparation of silicone sol
accurate amount of 50mL waterless ethanol placed in a 200mL beo bowl, in the stirring to add a certain amount of ethyl silica, and hydrochloric acid to adjust the pH of the solution, stirring 10min after adding distilled water, continue to stir 30min to obtain silicone solution.
1.3.2 preparation of silicone titanium sol
accurately take 100mL waterless ethanol placed in a 500mL beo bowl, add a certain amount of butyl titanate and a small amount of acetyl acetone under stirring, and adjust the pH of the solution with hydrochloric acid, stir 10min after adding distilled water, stirring 30min to obtain titanium solution. The silicone sol is slowly added to the titanium sol, and the colorless transparent silicone titanium sol is obtained after stirring for a certain period of time. And with waterless ethanol to double the silicon titanium sol, you have to clean the paint.
1.4 photo catalytic activity test
1.4.1 photo catalytic activity test one
each accurately measured 30g of the sample to be placed in the numbered test tube, to each test Add 2g pre-matched methyl orange solution (0.1mg/mL) to the tube, stir well, place the test tube 60cm from the ground with ultraviolet light, take pictures at different times, observe color changes.
1.4.2 photo catalytic activity test II
preparation concentration of 0.1 mg / mL meth orange solution, poured on the glass plate sprayed with self-cleaning paint, the glass plate placed 60 cm from the ground with ultraviolet light exposure, in different time periods to take pictures, observe color changes.
1.5 Outdoor Test Expedition
sprayed homemade self-cleaning paint on a 60cm×70cm glass plate and placed it on a homemade outdoor test stand to observe its anti-fouling capabilities.
results and discussion
2.1TiO2/SiO2 sol infrared spectra
Figure 1 is the infrared spectra of TiO2/SiO2 sol, 3434.32cm-1 Absorption peaks of OH in structural water, 1634.05cm-1 for physical adsorption water - OH absorption peaks, 1456.92cm-1 and 1398.61cm-1 for - CH The curved vibration peak of the C-H key in 3, the non-symmetric vibration peak of the Si-O-Si key at 1100.39cm-1, the 792.66cm-1 and 649.07cm-1 are affected. The symmetrical vibration peak of The Si-O-Si key affected by Ti, 962.75cm-1 is the vibration peak caused by Si-O-Ti key, and 547.95cm-1 is the vibration peak caused by Ti-O-Ti key. As can be found from the analysis in Figure 1, TiO2 and SiO2 in TiO2/SiO2 sol are both independent phases and have complexes of TiO2 and SiO2.
effect of 2.2 test temperature on hydrotherapic properties
Figure 2 shows the contact angle of the TiO2/SiO2 composite film made at different temperatures when the pH of the solution is 2.5. As can be seen from Figure 2, the contact angle of the TiO2/SiO2 composite film is also increased as the test temperature increases. This may be as the test temperature increases, TiO2 particle grain is larger, less than the surface area, the smaller the proportion of surface atoms, the amount of OH freelance on the coating surface is also reduced, the hydrophobicity of the composite coating is reduced.
effect of the pH of the solution on hydrotherapic properties
Table 1 lists the contact angles of the TiO2/SiO2 composite film made at different pH values at a test temperature of 5 degrees C. As can be seen from Table 1, with the increase of pH, the contact angle of the Resulting TiO2/SiO2 composite film also increases, and when the pH of the solution is 6, butyl titanate hydrolysates to form TiO2 powder, which cannot form TiO2/SiO2 sol. This is because hydrochloric acid as an hydration inhibitor of butyl titanate, when the pH increases, butyl titanate hydrolytic speed is faster, the formation of TiO2 particle size is larger, so tiO2/SiO2 composite film contact angle also increased, when the pH of the solution continues to increase, butyl titanate hydrolytic speed is very fast, butyl titanate hydrolytic formation of TiO2 powder.
effects of different TiO2 content on hydro-hydro properties
Figure 3 shows the contact angle of the TiO2/SiO2 composite film formed by different TiO2 content. As can be seen from Figure 3, the contact angle of TiO2/SiO2 composite film is the smallest with the increase of TiO2 content, and the contact angle is the smallest when TiO2 content is 50%. This is because with the increase of SiO2 content, SiO2 in the sol inhibits the growth of grains, the smaller the size of the surface grain, the larger the proportion of surface atoms, the amount of OH free-form on the coating surface also increased, the hydrophobility of the composite coating increased. When the SiO2 content is more, tiO2 surface is occupied by more SiO2, TiO2's effective surface is reduced, not easily affected by light excitation to produce hydro-water-producing areas, so the contact angle is larger.effect of 2.5 coating layers on hydro-hydroferrium performance
fgication 4 shows the contact angle of the TiO2/SiO2 composite film made when the test temperature is 5 degrees C, the pH value is 2.5, and the TiO2 mass fraction is 50%. As can be seen from Figure 4, the number of coating layers increases, and the contact angle of the TiO2/SiO2 composite film is gradually reduced, but after coating 3 layers, the degree of decline of the contact angle decreases gradually. Ultraviolet light is easy to pass through a single-layer or even double-layer film, low utilization rate of light energy, less hydromassive substances, resulting in a larger contact angle. With the increase of the number of thin film layers (i.e. thickness), the absorption of ultraviolet light increased, hydromassive substances increased, while the roughness of the film surface also increased, which is beneficial to hydromassiveness, when the number of thin film layers increased to the third layer, the inner TiO2 can not contact with water, the effect on hydromassiveness is small, so the contact angle does not change much. Therefore, from the cost point of consideration, the number of coating layers is set at 3 layers.
effect of different speeds on hydrophoto performance
Figure 5 shows the contact angle of the TiO2/SiO2 composite film with a test temperature of 5 degrees C, a pH of 2.5, a TiO2 mass score of 50%, and a coating layer of 3 layers. As can be seen from Figure 5, the coating speed increases, and the contact angle of the TiO2/SiO2 composite film is gradually reduced, but the degree of change is gradually reduced. Because the higher the speed, the smaller the size of tiO2, so the Contact Angle of the TiO2/SiO2 composite film is also reduced. When the speed increases to a certain extent, the degree of influence of the speed on the contact angle decreases, so the contact angle changes little. Therefore, the speed is set at 1500r/min.
2.7 photo catalytic activity test
2.7.1 photo catalytic activity test one
Figure 6 represents a comparison of homemade self-cleaning coatings with photo catalytic tests of other samples. As can be seen from Figure 6, after exposure to ultraviolet light, the color of methyl oranges in the self-cleaning paint is significantly lighter, and there is little change in the color of 1, 4, and so on. It is stated that the homemade self-cleaning coating has obvious photo catalytic activity.
2.7.2 Photo catalytic activity test II
apply a layer of homemade self-cleaning coating on the glass plate, after natural drying, pour a small amount of pre-matched methyl orange solution on the coating surface, put the plate under ultraviolet light, observe color changes. As can be seen from Figure 7, after exposure to ultraviolet lamps, the color of methyl orange disappears, indicating that homemade self-cleaning coatings have better photo catalytic activity.
2.8 Outdoor Test
Figure 8 is a picture of a model placed outdoors after Jan. Visible from Figure 8, sprayed since the cleaning paint, sprayed self-cleaning paint glass surface is relatively clean, and the uncoated glass surface has obvious traces of rain, and after the rain rinse surface has mud, it can be seen that after spraying self-cleaning paint, the glass surface is easier to clean, and after cleaning relatively clean, indicating that homemade self-cleaning paint has a better anti-fouling ability.
3. Conclusion
(1) The contact angle of the TiO2/SiO2 composite film made at a temperature of 5 degrees C, pH of 2.5, TiO2 mass fraction of 50%, coating layer of 3 layers, and speed of 1500r/min is 6.8 degrees.
(2) through photo-catalysis and outdoor testing, it is shown that homemade self-cleaning coatings have good photo-catalytic effect and anti-fouling properties.
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