Study On Preparation And Application Of Waterborne Coatings Obtained From Polymer Emulsions

Coatings are a kind of materials coated on the surface of an object, which can provide the object decorative, protective or particular functions. Waterborne coatings that use polymer emulsion as film-forming component are being paid attention to by more and more scientific and technical personnel and the application field of waterboene coatings has become more widely.The preparation and application performance of three waterborne coatings which use different polymer emulsions as film-forming component have been investigated in this paper, and a classification method of coating adhesion and measuring method of rust area of coatings based on the Photoshop software have also been proposed. The main work of this paper is as follows:1. The waterborne crack decorative coatings were prepared by two-component epoxy basecoat and topcoat made from one of the fluorine-containing acrylic emulsion, silicone-acrylic emulsion and styrene-acrylic emulsion. Compared with the traditional solvent-based paint, the waterborne coatings are environmental friendly and non-toxic. Crack decorative coatings can be applied to the surface of wall, glass, furniture or works of art and so on. The mechanism of crack patterns generation was analyzed. The factors that influence the crack spacing and crack shape of crack patterns were investigated. Different crack spacing and crack shape of the crack pattern were prepared by changing the film thickness, topcoat type, pigment content, the air flow rate of coating surface and other factors. Three junction types of crack patterns were prepared by the three top coatings, which were T-junction, Y-junction and mixed junction. T-junction type was made from styrene-acrylic emulsion. Y-junction type was made from fluorine-containing acrylic emulsion and mixed junctions type was made from silicone-acrylic emulsion. The crack spacing increased with the increase of the thickness of topcoat. The higher content of pigments and fillers, namely the greater the pigment to binder ratio, the more difficult of topcoat cracking. In the process of film drying, the increase of air flow speed on coating surface can result in smaller crack spacing of crack patterns. The properties of coating film including adhesion, water resistance, scrub resistance and so on were tested. The results showed that the crackle coatings possessed satisfactory properties for practical application. 2. The waterborne fluorine-containing exterior coatings were prepared using fluorine-containing polymer emulsion, whose preparation and application performance, especially the coatings’ weathering durability was investigated. The coatings’ weathering durability mainly determined by the changes of color, gloss and hydrophobicity. Color change, gloss change and change in hydrophobicity were measured by whiteness meter, gloss meter, and contact angle measuring instrument. Artificial aging test of coatings was carried out for 1000h in Xeon Lamp Aging Test Chamber. The fluorine-containing coatings made from weather-resistant rutile TiO2, DuPont R706, were without peeling, no blistering, and color changed slightly. After the outdoor aging under natural conditions for one year, during which the coatings undergoing sunlight, rain, diurnal variation, the fluorine-containing coating film were without peeling, no blistering and no color change. The fluorine-containing coatings were tested by National Test Center of Polymer and Chemical Building Materials in Beijing, the test results met or exceeded national standard for synthetic latex wall paint of GB/T 9755-2001 synthetic resin emulsion coatings for exterior wall.3. To solve the environmental problem of Cr in silicon steel sheet coatings, silicon steel sheet coatings without Cr were prepared by using acrylate polymer emulsion and a multi-tooth metal chelating agent. The multi-tooth metal chelating agent was used as anti-rust component, instead of the traditional components of toxic Cr. The chelating agent formed many chelate rings on the surface of silicon steel during film forming, which forming compact single-molecule protective film. This film can effectively prevent the O2 and the water getting into the silicon steel surface, and sequentially inhibit the oxidation corrosion of silicon steel. The templets of chrome free silicon steel sheet coatings were tested by the Guangzhou National Quality Supervision and Inspection Center for Household Electrical Appliances for the hot-resistance and refrigerant-resistance performance. The test results showed that the coatings fully met the requirements of coating for silicon steel sheet.4. A method of paint adhesion classification and coatings rust area measurement was proposed, in which the Photoshop processing software and a scanner were introduced. Based on the flexible select image methods and the statistical function to the image pixel of Photoshop software, the classing method of film adhesion by using Photoshop software and scanner was proposed. The pixel was the relative area in this method. This method was more accurate than the commonly used method of image comparison. The percent area removed given by ASTM standard and the percent pixels removed measured by Photoshop was correlated, with the correlation coefficient being 0.997. Likewise, based on the flexible select image methods and the statistical function for the image pixel, combined with the height and width measurement function in "Info" panel for the image, the rusty areas can be quantitatively determined by using A’=X’/X×A. For regular rust area, the area calculated by Photoshop software and that measured by a vernier caliper and were compared. The determining error of rusty areas was under 3.0%. This proved the veracity of the result measured by Photoshop software.