U.S. Naval Research Develops Safer Topcoat for Aircraft

The Marine Corps AH-1Z Viper helicopter was recently painted with a 1K camouflage gray polysiloxane topcoat on the exterior. Photo by Victor Chen, NRL.

The U.S. Naval Research Laboratory’s (NRL) (Washington, DC, USA) Center for Corrosion Science and Engineering has developed a safer and user-friendly topcoat that was recently applied onto the exterior of Navy and Marine Corps aircraft. The topcoat, which is a one-component (1K) polysiloxane based on organosilane polymers, is a new technology that is free of harmful isocyanates and other hazardous air polluting (HAP) chemicals.

Isocyanates and HAPs are found in two-component (2K) polyurethane topcoats currently used on U.S. Department of Defense (DoD) and commercial aircraft. Erick Iezzi, a senior research chemist at NRL, applied the new topcoat with Naval Air Warfare Center–Aircraft Division engineers onto a U.S. Navy F/A-18 Hornet located at Naval Air Station Patuxent River in Maryland, USA. Additionally, the topcoat was applied to multiple U.S. Marine Corps helicopters.

The topcoat on these aircraft is scheduled for an evaluation period of one to two years. “We're very proud of this achievement,” Iezzi says. “Polyurethane topcoats have existed for several decades, yet within a few years we've been able develop an environmentally friendly alternative that provides similar laboratory performance and is easy for painters to use.”

Replacing isocyanates with polysiloxane provides a safer coating for painters and anyone conducting maintenance in nearby areas, according to NRL. The topcoat also contains lower levels of volatile organic compounds, which negatively impact air quality during spray applications.

The topcoat requires no metering or mixing of components because all chemicals are in one container, thus reducing time of preparation and providing a more homogeneous color. The container is also resealable for future use, which reduces hazardous waste and disposal costs.

While NRL chemists previously developed coatings for surface ships, they say the requirements for aircraft coatings are more demanding. “Developing a new high-performance topcoat for aircraft is more difficult than for ships,” Iezzi says. “Aircraft have aluminum skin, which means the coating must provide greater flexibility, especially at cold temperatures during high-altitude flight. An aircraft topcoat must also retain a camouflage appearance for longer periods of time.”

The polymers and coating technology are covered by U.S. patents, which are licensed by NCP Coatings, Inc. (Niles, Michigan, USA). NCP produces the camouflage topcoat for demonstrations and field validation. The company is using this technology to develop semi- and high-gloss formulations.

The applications were coordinated with the Naval Air Systems Command and sponsored by the DoD’s Environmental Security Technology Certification Program, with contributing funds from the U.S. Office of Naval Research.

Source: U.S. Defense Visual Information Distribution Service, www.dvidshub.net.