Organic topcoats are the primary source of barrier-type protection against environmental degradation of Department of Defense (DoD) systems. Standard topcoats contain high levels of solvents and volatile organic compounds (VOCs). Since the painting process releases these VOCs as hazardous air pollutants (HAPs), current coatings create hazards for workers and air pollution concerns for the facility. Hazardous waste disposal is also an issue. A single Navy Depot typically discharges over 15,000 pounds of solvent per year from coating operations. This project demonstrated a new topcoat formulation built on the advances in polymer chemistry that use water-dispersible resins and do not require organic solvents for viscosity reduction and spray application. In this novel polyurethane coating, the polymer exists in an organic phase surrounded by water that provides the necessary liquid medium. After application, the water evaporates and allows the binder and pigment particles to fuse into a continuous film. The topcoat was demonstrated on full aircraft, aircraft components, and support equipment.
Laboratory testing followed by some initial outdoor exposure tests indicated that there were some deficiencies that needed to be addressed before moving to full-scale demonstrations. These included short pot life, insufficient elongation capability at low temperatures (i.e., flexibility), resistance to high temperature, and chalking during outdoor exposure. These deficiencies were overcome through reformulation and the development of clear mixing and application instructions. In full-scale field-testing, the zero-VOC topcoat was applied to the outer wing panels of a C-2 aircraft, components of a CH-46 helicopter, an EA-6B jet, two F/A-18 fighter jets, a CH-60S helicopter at the original equipment manufacturer (OEM), and various pieces of support equipment. Tow bars were deployed aboard the USS Harry S. Truman for six months and remained topside for the entire deployment. After deployment, these tow bars looked slightly better than similar tow bars painted with the standard solventborne topcoat. The remainder of the demonstrations will continue through calendar year 2002 when comparisons will be made to similar assets painted with the standard topcoat.
Successful demonstration and validation of the zero-VOC topcoat will aid the transition of the technology to service facilities and the process of gaining regulatory acceptance. The new topcoat will virtually eliminate VOCs from the topcoating process. By eliminating VOCs, the facilities can avoid regulatory fines and required emission controls. Reduction in the volume of hazardous waste generated will reduce hazardous waste handling and disposal costs. Furthermore, elimination of VOCs will decrease exposure of workers to solvents by up to 35 percent. Finally, since facilities will remain in compliance, downtime will decrease and operational readiness can be maintained more efficiently.
The zero-VOC topcoat is a technically feasible means to reduce VOCs and HAPs from the painting process. According to cost analysis, reductions of 31,200 pounds per year of Toxic Release Inventory (TRI) materials; 68,800 pounds per year of TRI chemicals; and 145,000 pounds per year of hazardous waste reduction will be realized by implementing the new topcoat. However, this is based on 90 percent implementation at 66 Navy sites. Further reductions will be realized if the zero-VOC topcoat is implemented at other government sites and OEMs. (Project Completed - 2003)