A new camouflage paint has proved effective at concealing soldiers from the enemy and protecting their faces and hands from the searing heat of bomb blasts, researchers say.
Firefighters may also benefit from the new heat-resistant makeup, say University of Southern Mississippi scientists, who presented their research last week at a meeting of the American Chemical Society in Philadelphia.
‘Literally Cook the Face’
The research, initiated at the request of the Defense Department, is aimed at reducing the toll from roadside bomb blasts that have killed, burned and maimed soldiers in Iraq, Afghanistan and other conflicts.
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|Camouflage face paint has been used for centuries to conceal soldiers. Soon, it may also protect them.|
“The detonation of a roadside bomb or any other powerful explosive produces two dangerous blasts,” said Robert Y. Lochhead, Ph.D., who presented the research.
“First comes a blast wave of high pressure that spreads out at supersonic speeds and can cause devastating internal injuries,” he said. “A thermal blast follows almost instantaneously. It is a wave of heat that exceeds 1,112 degrees Fahrenheit. That’s as hot as a burning cigarette. The thermal blast lasts only two seconds, but it can literally cook the face, hands and other exposed skin.”
Ultrathin Protective Coating
To reduce that threat, ACS reported, the Defense Department sought a new material that soldiers could smear on their faces like sunblock, leaving a thin coating that could protect against high heat.
Lochhead admits now that he did not think it could be done. But he and his team found otherwise, developing a formulation that protects in laboratory experiments well beyond the two-second heat-wave threat from improvised explosive devices (IEDs) and other bombs.
For centuries, soldiers have used face paint for camouflage, Lochhead noted.
The new material meets that need but also protects the face and hands for up to 15 seconds before its own temperature rises to the point where a first-degree, or mild, burn might occur.
In some tests, researchers said, the new face paint can protect for up to 60 seconds, which could be important in giving soldiers time to move away from blast-related fires. It could also buy critical time for civilian firefighters.
The makeup had to meet several key criteria, according to ACS. It had to reflect intense heat; have camouflage colors suitable for day and night use; be easy to apply and remove; be waterproof; and be non-irritating to the eyes, nose and mouth.
Finding pigment particles of the proper size was also important. Conventional makeup pigments fall in the 100 to 500 nm range—too small for reflecting heat. “Lethal ballistic heat waves have wavelengths of 1,000 to 8,000 nm,” Lochhead said. “If pigments were to scatter or reflect these heat waves, the particles would have to be larger than the wavelength of the heat—that is, larger than 10,000 nm.”
Most challenging: The team had to avoid the use of mineral oil, mineral spirits, fatty substances and other traditional hydrocarbon makeup ingredients, which can burn in contact with intense heat in the flame spectrum, researchers said.
Instead, the team turned to silicones, which are not as flammable because they absorb radiation at wavelengths outside the intense heat spectrum. Silicones have been replacing hydrocarbons in many commercial cosmetic makeup products as cosmetics companies improve products to confer better feel properties and transfer-resistance, according to ACS.
Another challenge was adding DEET, an insect repellent. The military mandates that all camouflage makeups contain 35 percent DEET.
However, “DEET also is flammable, so when the Department of Defense asked us to incorporate it, we didn’t think we could do it,” Lochhead said.
In the end, however, the team was able to encapsulate the DEET in a hydrogel substance, a water-rich material that prevented the insect repellent from catching fire.
So far, thermal tests indicate the new makeup is able to keep surfaces from reaching 60 °C—the temperature at which skin burns—for 10 to 27 seconds, depending on pigment color. That’s far greater than the four seconds the military requires.
The coating has proved successful in preliminary laboratory tests, green-lighting additional development. The military is also currently conducting wear and comfort tests.
Lochhead’s team also plans to test the material on other surfaces to try to protect clothing, tents and other items from burning, and is developing a colorless version for firefighters.