Technology Transfer Network - Air Toxics Web Site
Converting to high-solids coatings typically involves reformulating sealers and/or topcoats, and generally is an easy transition for the facility. When the coating system has a higher solids content, the amount of volatiles released as the coating cures is decreased, resulting in a direct reduction in facility emissions. Because sealers and topcoats can account for up to 65 percent of finishing emissions, the potential emissions reduction can be significant. Traditional solvent-borne nitrocellulose sealers and topcoats have an average solids content of less than 20 percent, while high-solids sealers and topcoats can contain from 30 to 50 percent solids.
Reformulated high-solids coating systems generally are catalyzed conversion systems. In a catalyzed conversion system, the coating is cured partially through a polymerization reaction that creates a more durable and chemical resistant coating. However, the high-solids coatings are similar to traditional coatings because they are still solvent-borne, so the application method and coating behavior during application do not change significantly allowing the operators to easily adjust to the new coating system.
Other advantages of high-solids coatings include reduced solvent waste and better coverage because of the higher solids content. One application of a high-solids coating can place twice the amount of solids on an item using less solvent. This increased coverage can lead to cost savings if the cost per gallon of coating did not increase substantially with the reformulation. However, the increase in solids content also results in an increase in viscosity, so adjustments to application equipment may be required. Some facilities heat the coating before application to reduce its viscosity.
The potential VOC/HAP emissions reductions associated with the use of high-solids coatings are not as great as the reductions that can be achieved using the other low-VOC/HAP coating technologies. The coatings are still solvent-borne and a significant amount of solvent evaporates as the coating dries. From a pollution prevention perspective, high-solids coatings are an improvement over traditional solvent-borne coatings, but other technologies can provide a finish of equivalent quality with a greater VOC/HAP emissions reduction.
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