Formulating High-Performance Waterborne Epoxy Coatings
Primer Pigmentation The PVC should be in the range of 30-45%. Optimums are usually found in the range of 35-40%. Lower PVC levels generally result in lower application solids, early blistering at high humidity, and greater tendency to flash rusting. Table 9 summarizes typical pigment levels. Table 9. Typical Primer Pigmentation Levels
Pigment Type Anti-corrosion pigment Color pigment (e.g. red iron oxide) Extender Pigments calcium metasilicate silica-alumina ceramic microspheres barium sulfate mica Total % Volume 5.4-8.5 4.9 12.5 10.1 1.2-4.4 0.9 ~38
Type 5 Waterborne Epoxy Formulations Using the principals summarized above, the Type 5 waterborne epoxy was used to formulate a white enamel, a white primer, and a red iron oxide primer. These formulations are summarized in Table 10. The performance of these coatings is summarized in Table 11. The performance of the waterborne enamel is compared to that of a conventional solvent based epoxy enamel. The performance of the waterborne coating is equivalent to that of the solvent based coating, with the exception that the waterborne coating gives low VOC (1.53 lb/gal), more rapid dry, and superior corrosion resistance in the salt spray test. The waterborne primers give fast dry and excellent corrosion resistance.
Thermoset Resin Formulators Association 2006 Annual Meeting September 11-12, Montréal, Québec, Canada
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