Preserving Industrial Equipment with Acryllic UrethanePenncoat Inc
We at PennCoat frequently use an acrylic urethane mastic called Durethane DTM, manufactured by PPG. It can be used to put a hard protective coat on metals, concrete and masonry. The product can produce a high gloss and can be tinted in various hues, with good color retention. It has low amount of volatile organic compounds (VOCs), resists the sun’s ultraviolet rays and is fairly easy to apply. Durethane DTM is a two-component system consisting of a resin and a solvent that is mixed just before use to yield an acrylic urethane that builds a thick, high-solid surface without requiring a lot of substrate preparation. The shelf life of the unmixed components is three years from date of manufacture.
Component A of Durethane DTM is the solvent and colorant. Butyl acetate (C6H12O2) is one of the principal solvents, composing 7 to 13 percent by weight. Another solvent, parachlorobenzotrifluoride, or PCBTF (C7H4ClF3), is present in approximately the same proportion and is favored in polyurethane finishes for its low VOC content. Component A is white thanks to a 10 to 30 percent concentration of titanium oxide, but various tints are available.
Component B is a hardening resin composed of hexamethylene diisocyanate, or HDI (C8H12N2O2), which forms a coating that is resistant to abrasion and UV radiation. The two components are mixed in the ratio five parts A to one part B. Optionally, you can mix in a urethane accelerator to reduce the drying time and/or a tint to color the product. PPG recommends the use of PerformColor 4257 colorants to tint Durethane DTM. When applied, the mixture forms a film 3- to 5-mils thick. The mixed product is about 65 percent solids by volume with a VOC content of 2.01 lbs/gal. At a dry film thickness of 4 mils, expect a spread rate of 261 square feet per gallon.
Preparation and Application
Pre-mix Component A at a moderate speed with a pneumatic air mixer. Add Component B and continue to mix for one to two minutes longer. The surface should be clean, dry and free of contamination. It’s best to apply the coating in stable temperature conditions to avoid dimensional instability. If applying to a previously painted surface, test that surface’s adhesion to make sure it isn’t lifted by the Durethane. Normally, Durethane is self-priming, but you might want to separately prime heavily rusted metals. You can use a suitable epoxy primer for concrete. Once you mix the two components, you have about three hours to complete the application (less if you added accelerant). You can apply Durethane DTM with a conventional spray (E or F tip with needle), airless spray (tip size 0.331 – 0.443mm, 2,500 psi, use thinner), natural bristle brush or roller (3/8-inch nap with solvent-resistant core, can use flow control additive). Naturally, you’ll want to observe proper ventilation conditions and keep the material away from flames or sparks.
PPG recommends that you do not apply the product when the temperature of the air, surface or product is below 40°F, with the surface temperature no less than 5°F above the dew point. The maximum conditions for application are 100°F air temperature and 85 percent humidity. You might choose to add up to 5 percent (by volume) zero-VOC PCBTF thinner to avoid putting down too thick a coat, which might trap air and cause pinholing. The dry-through time at 77°F and 50 percent humidity is less than one hour with accelerator, but 8.5 hours otherwise.
PennCoat, Inc. has been providing industrial painting, commercial painting, epoxy flooring, and polished concrete services for nearly 30 years. Our experienced installers are trained and equipped with the proper knowledge and tools to ensure that every installation is installed efficiently and safely. PennCoat, Inc. provides service to Pennsylvania, New Jersey, Maryland, and Delaware. And we cover York, Lancaster, Philadelphia, Chester, Montgomery, Baltimore, Harrisburg, Dauphin, Bucks, Berks, and other counties in the surrounding