Engineers at Picatinny Arsenal, N.J., are developing a new paint formula so soldiers will know if their ammunition is safe to use just by seeing what color it is, officials said.
“We have formulas that change color within the designated temperature ranges, but our biggest challenge is maintaining long-term stability of a coating,” said James Zunino, Project Officer / Materials Engineer, Armament Research, Development and Engineering Center (ARDEC). “We have to develop a paint that will survive in military operating conditions, including harsh temperatures and wind blasts.”
Referred to as Thermal Indicating Paints, the new paint formula uses thermochromic polymers to detect temperature ranges that ammunition was exposed to during transport or storage.
A mood ring is a common example of a thermochromic object. The ring changes color in response to the body temperature of the person wearing it. The thermochromic element changes the wavelength of light when it is exposed to different temperatures.
The same basic concept applies to thermal indicating paints for ammunition, but Picatinny’s challenge is ensuring the color change is permanent.
Throughout combat operations, ammunition is often exposed to extreme temperatures during transport, storage and pre-positioning. Research shows that Middle East combat operations temperatures inside munitions’ containers can exceed 190 degrees Fahrenheit, officials said in a statement.
Storing ammunition at too high temperatures can compromise the integrity and performance of the round. Further, using the overexposed round can lead to increased safety risks for the warfighter.
When propelling charges are exposed to high temperatures for extended periods, the propellant stabilizer can be rapidly depleted, creating the potential for auto-ignition. Additionally, if the overheated propellant is fired, it can lead to dangerous, elevated gun pressures that could cause weapon failure and put soldiers at risk of injury.
There have been documented incidents of failures caused by thermal exposures during Desert Storm and the recent conflicts in Iraq and Afghanistan, the officials said.
“Thermal indicating paints can help prevent warfighters from using ammo that may have been compromised by exposure to environmental conditions outside of design limits,” Zunino said. “It could reduce the amount of accidents that could happen, it can reduce the logistical burden of transporting and storing munitions, and it gives increased survivability to the soldier.”
ARDEC uses in-house testing equipment at Picatinny to test various formulations of the paints. The team is partnering with the New Jersey Institute of Technology (NJIT) to develop a formula that can provide an irreversible, permanent color change to indicate specific temperature ranges on munitions.
“Working with NJIT has been exceptional. We work very closely with one another–it’s much more than just e-mail correspondence,” said Giuseppe Di Benedetto, ARDEC Technical Lead / Chemical Engineer.
The team is developing cost effective and commercially available formulations that can detect four heat ranges–all in degrees Fahrenheit–145-164, 165-184, 185-200, and above 200. The first round to be tested will likely be the 30mm High Explosive (HE) round.
The paint coating has potential to be much more cost effective, pennies per application compared to costly temperature gauges the Army currently uses on its larger caliber ammunition stocks.
“We’re starting with the 30mm family of ammo, because they aren’t expensive enough rounds to deem the use of a costly temperature gauge or monitor,” Zunino said. “The savings are bigger because it’s low value, high volume assets.”
The team plans to have a formula ready for trial testing within the year, he said.
The Project Director Joint Services, a division of the Program Executive Office for Ammunition headquartered at Picatinny, manages the program and will coordinate the Army’s acquisition and fielding efforts on the new paints.
“The desired outcome in the Class V (ammo) world would be a very inexpensive telltale that soldiers and logisticians could use to identify munitions that had experienced temperature exposures outside design limits,” said Mitch Hillard, program specialist, PD Joint Services. “Such munitions could then be set aside for test and analysis to provide feedback to the development community on the performance and safety effects of extreme environmental exposures.”