The objective of this project was to demonstrate and validate low-volatile organic compound (VOC), quick-curing aerospace coatings for multiple weapon systems. Conventional aerospace coatings of the type evaluated typically contain high levels of VOCs and hazardous air pollutants (HAP) and are applied to relatively high thicknesses. Applications of these coatings are labor and time intensive, typically requiring several hours and multiple work shifts to complete and leading to bottlenecks in production and Programmed Depot Maintenance (PDM) processes. The solvents used in these coatings, such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), toluene, and xylene lead to VOC and HAP emissions that often exceed 400 grams per liter. Because of the relatively high coating thicknesses required, application of these coatings may comprise a significant portion of a facility's overall emissions that are subject to National Emission Standards for Hazardous Air Pollutants (NESHAP). The continued use of these coatings presents logistical and safety requirements at production and PDM facilities.
Two low-VOC, quick-cure coatings—FP 212 and FP 60-2—were demonstrated for different weapon systems. Through the use of exempt solvents, the VOC contents of these coatings are significantly lower than the baseline coatings. The solvents used in the formulations of these coatings have relatively high vapor pressures, which allow much of the solvent to evaporate before reaching the substrate. The result is that relatively high build rates (mils per pass) are achieved as only small quantities of solvent remain in the wet coating that reaches the substrate. Improved curing agents, as well as high vapor pressures of the solvents, result in relatively quick cure times for the coatings. Both coatings are formulated with an improved polyurethane resin and are applied as admixed materials, allowing use of conventional manual spray or robotic spray application methods.
Both coatings passed all laboratory-scale qualification testing for the selected weapon systems. Additionally, application studies were performed with FP 212 and FP 60-2 on full-scale engineering prototypes of proposed weapon system areas of application. Results showed that FP 60-2 requires significantly less time to reach desired thickness and cures much more quickly than the baseline. FP 212 showed similar application advantages but to a lesser extent. The application properties of both coatings improved significantly when applied under elevated temperature and humidity conditions. It also was discovered that the new resin used in the formulation of FP 212 and FP 60-2 resulted in drastic durability improvements in maritime environments compared to the baseline coatings. Results showed that FP 212 and FP 60-2 should last two to three times longer in maritime environments compared to baseline coatings. It is expected that these coatings will show similar durability benefits in non-maritime environments as well. FP 212 and FP 60-2 represent drop-in replacements for the baseline coatings.
The demonstrated coatings will result in significant life-cycle environmental and economic benefits. The improved application properties demonstrated during the full-scale application studies will result in decreased labor hours required for material application and decreased production and PDM flow times. Increased durability of the coatings in maritime and other environments will virtually eliminate depot-level repairs of these coatings over the normal aircraft lifetime, which will decrease downtime, costs, and emissions associated with repairs. The drop-in replacement capabilities of FP 212 and FP 60-2 will minimize training requirements and eliminate equipment and facility modifications. It is anticipated that life-cycle VOC and HAP emissions for the weapon systems of interest will decrease by 270,000 pounds and 328,000 pounds, respectively. Life-cycle cost savings of transitioning FP 212 and FP 60-2 to production and PDM processes of the weapon systems of interest are expected to result in a net present value of approximately $50 million. (Project Completed - 2007)