Characterization of curing emissions from conversion varnishes

Three commercially available conversion varnish coating "systems" (stain, sealer, and topcoat) were selected for an initial scoping study. The total volatile content of the catalyzed varnishes, as determined by U.S. Environmental Protection Agency (EPA) Method 24, ranged from 64 to 73 weight%. Uncombined (free) formaldehyde concentrations, determined by a sodium sulfite titration method, ranged from 0.15 to 0.58 weight% of the uncatalyzed varnishes. Each sealer and topcoat was also analyzed by gas chromatography (EPA Method 311). The primary volatile organic constituents included methyl ethyl ketone (MEK), isobutanol, n-butanol, methyl isobutyl ketone (MIBK), toluene, ethylbenzene, the xylenes, and 1,2,4-trimethylbenzene. Dynamic small chamber tests were performed to identify and quantify emissions following application to coupons of typical kitchen cabinet wood substrates and during curing and aging. One of the objectives was to determine the relationship between the concentration of solvents [hazardous air pollutants (HAPs) and volatile organic compounds (VOCs)] and formaldehyde measured in the coatings' formulations and the emissions released during curing, after the coatings were applied. The results to date have shown good mass balance (amount of a constituent applied versus amount emitted) for the individual WAPs (except formaldehyde) and VOCs identified in the sealers and topcoats. Formaldehyde emissions have shown six to seven times the emission compared to the free formaldehyde content in the formulation, indicating that formaldehyde is formed during the curing process. Results of the formulation analyses and emission tests completed to date are described in this paper.