What is a waterborne coating?
Any coating with water as solvent or dispersion medium can be called water-based coating. Waterborne coatings include water-soluble coatings, water-dilutable coatings and water-dispersible coatings (latex coatings). Water-soluble coatings are mainly water-soluble resin, represented by polyvinyl alcohol and its various modifications, in addition to water-soluble alkyd resin, water-soluble epoxy resin and inorganic polymer water-based resin.
How about waterborne coatings?
Advantages of waterborne coatings:
1, water-based coatings use water as solvent, saving a lot of resources; Waterborne coatings eliminate the fire danger in the construction process; Reduce air pollution; Water-borne coatings only use a small amount of low-toxic alcohol ether organic solvents, which improves the working environment. Generally speaking, the organic solvent (the proportion of coatings) of waterborne coatings is between 65,438+00% and 65,438+05%, while that of cathodic electrophoretic coatings has been reduced to below 65,438+0.2%, which plays a significant role in reducing pollution and saving resources.
2. Waterborne coatings can be directly applied to wet surfaces and wet environments; Waterborne coatings have good adaptability and strong adhesion to the surface of materials.
3. Water-based painting tools can be washed with water, which greatly reduces the amount of cleaning solvent.
4. The electrophoretic coating of waterborne coatings is even and flat. Good flattening; The inner cavity, welding seam and edges and corners can be coated with a certain thickness, which has good protection; Electrophoretic coatings have the best corrosion resistance, and the salt spray resistance of thick film cathodic electrophoretic coatings can reach1200 h h.
Disadvantages of waterborne coatings:
1. Waterborne coatings require high cleanliness during construction and on the surface of materials. Because of the large surface tension of water, dirt is easy to cause shrinkage cavity in the coating film.
2. Waterborne coatings have poor dispersion stability to strong mechanical force. When the flow velocity in the conveying pipeline changes sharply, the dispersed particles are compressed into solid particles, which makes the coating film pockmarked. It is required that the conveying pipeline has a good shape and the pipe wall is free of defects.
3. Waterborne coatings are very corrosive to coating equipment, which requires anti-corrosion lining or stainless steel materials, resulting in high equipment cost. Waterborne coatings corrode pipelines, dissolve metals, precipitate dispersed particles, and produce pits on the coatings. Stainless steel tubes are also needed.
4. Baking waterborne coatings has strict requirements on the construction environment (temperature and humidity), which increases the investment and energy consumption of temperature and humidity control equipment.
5. Water-based coatings have high latent heat of evaporation and high baking energy consumption. Cathodic electrophoretic coating should be baked at 65438 080℃; But it takes a long time for latex paint to dry completely.
6. The high-boiling organic cosolvent of waterborne coatings produces a large amount of oil fume during baking, which drops on the surface of the coating film after condensation, affecting the appearance.
7. The poor water resistance of waterborne coatings makes the stability of coatings and bath solution poor, and the water resistance of coatings is poor. The medium of waterborne coatings is generally weakly alkaline (pH 7.5 ~ pH 8.5), and the ester bond in the resin is easy to hydrolyze and degrade the molecular chain, which affects the stability of coatings and baths and the performance of coatings.
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