Finding a Green Alternative to Vinyl Resin Coatings
Is it possible to identify or develop a coating product which would provide the advantages of a vinyl resin without the high VOC levels? Reclamation specified coatings must meet all Federal standard VOC regulations of 450 g/L, materials containing less than 250 g/L would allow use in California and 100 g/L or less would meet the most strict air quality requirements (southern California). The Army Corps of Engineers is interested in finding a possible substitute for vinyl resins to reduce VOC emissions as well as their reliance on a single product type for impact resistant gate coatings.
Need and Benefit
Vinyl resin coatings were utilized by the Bureau of Reclamation (Reclamation) and are currently used by the Army Corps of Engineers as a coating system that can achieve a 30-50 year service life in a majority of immersion service conditions. These coatings were commonly used by Reclamation on gates and other equipment which required a durable coating that could stand up to frequent UV exposure and immersion service. Vinyl resins rely on high fractions of VOC-containing solvents which pose health and safety and environmental concerns. The 1992 EPA VOC regulations placed a limit on the amount of solvent that coatings were allowed to contain which severely limited vinyl resins from use. The Army Corps of Engineers is the only organization that still uses these coating systems, but must maintain an exemption in order to apply the coating. The Army Corps of Engineers funded a company to develop a vinyl system using acetone as the carrier, unfortunately this product was not successful. In 2009, Dow Chemical discontinued the production of vinyl resins there is concern that these materials may become difficult to obtain in the future. Reclamation has used epoxies and cycloaliphatic epoxies as a replacement, but they chalk and degrade in UV light over time. Epoxy coatings are generally fairly brittle and cannot withstand impact damage. Another problem with epoxy coatings is that they slowly absorb water and the corrosion resistance decreases with time, whereas the vinyl resins provide excellent barrier protection over the life of the coating.
Existing coatings in use by Reclamation are inferior to vinyl resin coatings for fluctuating immersion especially where the structure is subjected to impacts. For example, epoxies chalk when exposed to UV light and aliphatic polyurethanes, acrylics, and polysiloxanes don't hold up well in long term immersion. Fluoropolymers are very expensive, must be baked on, and aren't typically specified for immersion service. A green replacement for vinyl resins could significantly reduce a coating's life cycle cost and VOC emissions. Coating maintenance costs are projected to increase in the coming years as the legacy coatings reach the end of their service lives and begin to require replacement. Any potential replacement materials will have a projected lifespan that is much shorter (15 years vs 30+ years) than the material being replaced.
Contact the Principal Investigator for information about partners.
Bureau of Reclamation Review
The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.
Finding a Green Alternative to Vinyl Resin Coatings (final, PDF,
By David Tordonato, Bobbi Jo E. Merten, Allen Skaja
Research Product completed on September 30, 2018