Objective: The Department of Defense (DoD) spends millions of dollars each year utilizing solvent-borne organic coatings to protect weapon system substrates. These coatings include chromated primers and topcoats containing high volumes of volatile organic compounds (VOC) and hazardous air pollutants (HAP) and present a significant burden for environmental compliance, permitting, tracking, storage, operations, disposal, and reporting requirements. The objective of this project is to demonstrate, validate, and implement a VOC/HAP-free low temperature cure powder coating on DoD weapon system components in a depot production environment. Technology Description: Low temperature cure powder coatings were developed through scientific analysis of powder coating chemistries and the discovery that an acid/epoxy reaction could facilitate a low temperature cure of powder coating. These studies led to the down selection of an acid functional polyester resin with a triglycidylisocyanurate crosslinker. Coating material development involved optimizing parameters such as catalyst, resin type, corrosion inhibitor, flow additive, pigment concentration, powder particle size, and the ratio of resin to crosslinker. The resultant coating developed under SERDP project WP-1268 is a VOC/HAP-free alternative to solvent-based coatings, and it features performance properties equal to or better than those of coating systems governed by commonly used specifications such as MIL-PRF-23377, MIL-P-53022, MIL-PRF-85285, and MIL-PRF-22750. The coating can be applied directly to the component substrate, eliminating the need for primers. This low temperature cure powder coating is fully curable at 250°F and can replace other powder coatings, which require temperatures between 280°F and 400°F. Decreasing the curing temperature enables temperature-sensitive substrates, such as tempered aluminum, to be powder coated safely, without compromising their structural integrity and performance. Although all powder coatings offer superior barrier protection against corrosion, the powder coating being examined also contains a corrosion inhibitor, barium metaborate, to further improve corrosion protection in the event of coating damage. Expected Benefits: Significant reductions in VOCs, HAPs, and hazardous waste disposal could result from implementing low temperature cure powder coating technologies. In 2004, an estimated 2 million pounds of VOC and HAP emissions resulted from wet paint and depaint operations at Air Force logistics centers. The new low temperature cure powder coatings have the potential to eliminate more than 95% of the toxic and hazardous materials currently being used for the targeted heat-sensitive substrates. Further, the coatings may be applied to these substrates to meet corrosion protection requirements without compromising the structural integrity of the component. (Anticipated Project Completion - 2009) Principal Investigator: Mr. Wayne Patterson
OO-ALC/MADL
Science and Engineering Laboratory
7278 4th Street, Building 10, Bay D
Hill AFB, UT 84056
Telephone: (801) 775-2992
Fax: (801) 775-2628
E-mail: wayne.patterson@hill.af.mil |
