International. A new study by researchers in Canada deals with water-based coatings that share the mechanism of action of oil-based coatings.
Because oil- or solvent-based coatings emit volatile organic compounds (VOCs), it is desirable to replace them with aqueous coating formulations. However, water-based (latex) coatings that are dispersions of polymer particles, are surpassed with solvent-based coatings in hardness, durability, brightness and application in cold climates.
The challenge with latex is that discrete polymer particles must come together to form a complete film, a complex process that often leads to imperfections in the coating. The results of the proof of concept show that CO2-sensitive copolymers can form the basis of a coating in water in which the polymer completely dissolves before application and yet resists water after application to a surface. These polymers are insoluble in neutral water, but dissolve completely in carbonated water.
When a carbonated polymer solution is poured over a substrate, the subsequent loss of CO2 and water by evaporation results in a water-resistant, transparent and continuous coating. With further development, these new coatings can retain the VOC-free advantage of water-based coatings, while eliminating the need for particle coalescence.
Source: Green Chemistry.
