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Smart coatings could help save soldiers' lives.

Scientists at the U.S. Armament Research, Development and Engineering Center (ARDEC) are developing cutting-edge armament technology solutions that save soldiers' lives. Located at Picatinny Arsenal in north central New Jersey, ARDEC is a specialized research, development, and engineering center within the U.S. Army Materiel Command that focuses on five major technology areas--advanced weapon systems, advanced energetics and warheads, fire control, logistics, and emerging technologies. Emerging technologies include networked lethality, defense against unmanned systems, counterterrorism technologies, homeland defense technologies, novel power and energy systems, manufacturing science technologies, and advanced materials/ nanotechnologies, some of the latter of which are based on smart coatings technology.

There are in fact four different efforts specifically targeting development of smart coatings--the Smart Coatings Materiel Program (SCMP), the Active Coatings Technologies (ACT) and Active Coatings Technologies on Roto-Craft (ACTOR) initiatives, and the Development of Active Sensor Systems for Military Utilization (DASSMU) project.

Engineers at ARDEC work with researchers at the New Jersey Institute of Technology (NJIT) on several of these projects. Initially, according to materials engineer James Zunino, the team at ARDEC worked to develop the concept of a multilayer coating system that could sense, analyze, and respond to stimuli in real time. "With this multilayer approach, we were pursuing the idea of creating a coating that acts like skin, which bruises when hit, turns red when cold/hot, and heals when damaged or injured," he explains. As they started to develop the components and technologies necessary to create such a smart coating, they realized that some were further along than others and some had stand-alone applications. The ACT program was formed to enable tailoring of coating systems based on specific applications such as Thermal Paints for Ammunition Assurance, Embedded Systems for Smart Skin of Vehicles, and others that cannot be publicly discussed. Active coatings, Zunino adds, are cost-effective ways to add sensing capabilities where electronics and conventional techniques are cost prohibitive or affect the system.

The smart coatings work at ARDEC has garnered significant attention. In 2009, for example, the engineers (including Zunino, Laura Battista, Nelson Colon, and the now retired Dr. Joseph Argento) won the 2009 Thomas Alva Edison Patent Award from the Research and Development Council for an anticorrosion smart coating system.

More recently, ARDEC's thermal indicating paint has been in the spotlight. The coating contains thermochromic materials based on polydiacetylenes (PDAs) that change color when exposed to different temperatures. This coating is designed to be applied to ammunition to indicate when the bullets have been exposed to extreme temperatures that can compromise their integrity and performance and therefore present a safety hazard to the soldier. The challenge for the engineers, according to Zunino, has been to make the color change permanent and also to ensure coating stability under a variety of harsh military operating conditions. ARDEC researchers have collaborated with NJIT on this project as well.

"The thermal paints are tailorable to provide indications that munitions were stored at temperatures beyond their designed limits," Zunino says. "They provide an easy color change indication that the warfighter can readily see and use to make decisions." Four different paints are being developed that will detect temperatures in four different ranges. Initial testing on small arms ammunition is underway and looks promising, according to Zunino. These bullets are less expensive and therefore are not monitored with costly temperature gauges such as are used for larger caliber ammunition stocks. The smart coating, of course, also must be very inexpensive for this application.

The thermal paints also have potential use in first responder (fire investigation, temperature warnings, etc.) and food packaging applications. Other color changing coatings may also be useful for indicating the onset of corrosion before structural/visual changes occur; in this case the oxidation/redox reactions cause the color change. Adds Zunino: "Color changing paints and materials can also be integrated with embedded sensors for numerous applications such as a smart skin for indicating stress, strain, humidity, shock, impact, etc."

In addition to anticorrosion and thermochromic paints, ARDEC is also investigating several other smart coating technologies including self-cleaning, UV activated, self-healing, electrochromic, electroluminescent, chemical/biological responsive, micropore-based, active intelligent clays, etc. At present, thermal indicating paints; multifunctional, perfluo-roalkylated polymer-based coatings with anticorrosion properties; anti-chemical/ biological agent coatings; and hydrophobic nanocoatings are the main focus, and, according to Zunino, are the closest to transitioning into practical applications. The nanocoatings are being developed with anticorrosion and antifouling capabilities and for numerous military (storage tanks, radomes, vehicles, vessels, etc.) as well as medical and optical applications.

The program researchers and engineers consider all possible options when developing these smart coating systems. Where possible, conventional resins and additives are incorporated or leveraged, but quite often new additives or resins and even completely novel coating systems are devised for a specific application, according to Zunino. He gives as examples entirely new ink formulations used with new deposition techniques and new classes of molecules and materials that can be made into coatings, composites, and films. As mentioned above, ARDEC is making use of polydiacetylenes, intelligent nano-clays, and many different nanomaterials, including metallic and nonmetallic particles, various nano-sized polymeric materials, and carbon and other nanotubes to develop advanced smart coatings.

"We try to make application-based solutions," Zunino observes. "For example, thermal paints for ammunition need to work and survive extreme operating and storage conditions, so we add different materials to the base coating to make the paints, such as different oxides and polymers for tunability, color stability, UV protection, adhesion, etc. In some cases, we use as the base coatings existing military coatings like Army CARC or Aviation Coatings. For the military in general, what we use or create must be able to survive military operation, storage, and transportation conditions. They may need to last 20+ years in storage and operate/survive anywhere in the world; at a minimum they have to meet military standards and specifications."

In addition to performance properties, the ARDEC researchers must also consider manufacturability. Where possible, the new smart coatings are designed to be produced using existing production methods in order to avoid increasing cost. "You can have a great system but if it is not cost effective to incorporate it, the Army won't use it. If you need a new process, the return on investment must be worth it," states Zunino. Case in point: a $20,000 coating system will not be applied on a $30,000 vehicle, but that same coating may be appropriate for a $100,000 weapon system. Coatings for Roto-craft and ships can be more expensive than on munitions. Zunino sums up by saying, "The technologies involved and the types of systems we develop have to fit the potential utilization."

Many of the smart coating projects that the ARDEC engineers have been working on are progressing through the Army's complex testing process and a few are already in use. Some of the embedded sensors based on novel inks were transitioned to PEO Aviation for testing and integration for use on the Apache. The group is working on a project for the Air Force that involves use of its multifunctional perfluoroalkylated polymer-based coatings for protection of underground fuel storage tanks. More testing must be completed on the thermal paints to validate multi-year storage and exposure survivability, according to Zunino. ARDEC does hold patents on several of the smart coatings technologies, and companies have expressed interest in licensing some of them for both military and commercial applications.

The U.S. Department of Defense (DoD) uses Technology Readiness Levels (TRLs) to monitor and categorize technologies to determine how ready they are for operational assessment. The smart coatings technologies developed at ARDEC are at numerous TRL stages and have short and long-term transition potential. The Program Executive Office (PEO) for Ammunition and the Project Director (PD) for Joint Services, Ammunition Logistics Division (AMMOLOG) have been working closely with Zunino and his colleagues to advance and transition technologies for their applications. There are also several new weapon system development projects to create next generation systems for the Army, Navy, Air Force, etc., and the smart coatings group has been working with those teams to try to find new applications and transition points for the Smart and Active Coatings technologies.

"It takes a long time and a lot of approvals to get a new coating system adopted, though," Zunino acknowledges. "The safety of the warfighter is goal one, and therefore a lot of testing, evaluation, and qualification are required before operational and field testing is approved."


"ARDEC is making use of polydiacetylenes, intelligent nanoclays, and many different nanomaterials, including metallic and nonmetallic particles, various nano-sized polymeric materials, and carbon and other nanotubes to develop advanced smart coatings."
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Publication:JCT CoatingsTech
Date:Nov 1, 2011
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