Because oil- or solvent-based coatings (e.g. paints, varnishes, sealants) emit volatile organic compounds (VOCs), replacement with aqueous coating formulations is desirable. However, water-based (latex) coatings which are dispersions of polymer particles, are out-performed by solvent-based coatings in hardness, durability, gloss and cold-weather application.
Dissolving in carbonated water
The challenge with latexes is that discrete polymer particles must coalesce to form a complete film, a complex process that often leads to imperfections in the coating. Proof-of-concept results show that CO2-responsive copolymers can form the basis of a water-borne coating in which the polymer is fully dissolved before application and yet water-resistant after application to a surface. These polymers are insoluble in neutral water, but dissolve fully in carbonated water.
Eliminating the need for coalescence
When a carbonated solution of polymer is cast onto a substrate, the subsequent loss of CO2 and water by evaporation results in a clear, continuous water-resistant coating. With further development, these new coatings may retain the VOC-free advantage of water-based coatings while eliminating the need for coalescence of particles.
The study is published in: Green Chemistry, Issue 8, 2018.
Picture - The new developed water-borne coatings share the mechanism of action of oil-based coatings. Source: Leigh Prather – stock.adobe.com