CAMOUFLAGE make-up that can protect troops from the heat of explosions is
being developed by British defence researchers. Wearing the cream could mean the
difference between a severe burn that needs a skin graft and a far less serious
injury.
The Ministry of Defence says burns from explosions account for up to 30 per
cent of British military casualties, and even superficial injuries can be
painful enough to severely hinder a soldier. The figure is so high because the
radiant heat and hot gases from blasts can injure over much greater range than
shrapnel. Exposed skin such as the face and hands are most at risk. Gloves and
cotton hoods can protect these areas to some extent, but soldiers often avoid
them because they are bulky and restrictive.
Now, Graham Cooper and Paul Dearden at Britain鈥檚 Chemical and Biological
Defence Laboratory at Porton Down near Salisbury have developed a skin cream
that blocks up to 80 per cent of the heat from explosions. To a standard
skin-cream base of glycerol and zinc oxide, they added fine particles of
titanium dioxide which, at a specific size, can reflect infrared radiation.
Conventional explosives produce intense pulses of near infrared light that can
burn the skin in less than 10 milliseconds.
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Making the cream reflective to IR was not enough, however. Explosions also
produce dangerously hot gas, so Cooper included a solid 鈥渕elt additive鈥� called
cetyl alcohol. This melts at 47 掳C, the temperature at which skin would
normally burn. So when hot gas hits the cream, the heat is absorbed in melting
the cetyl alcohol. Because cetyl alcohol has a high latent heat of
fusion鈥攖he amount of energy required to make it melt鈥攊t absorbs more
of the heat from the blast.
Cooper says that when the blast wave has passed, the melted additive
re-radiates the absorbed heat slowly and safely as it solidifies. 鈥淏ecause the
heat comes back more slowly, the bloodstream can transport the heat away,鈥� he
says.
The Porton Down team tested its mixture by setting off explosions near
cream-coated ceramic plates designed to have the same thermal properties as
skin. Thermocouples embedded in the plates recorded how much heat got through
the cream. The team also blasted cream-covered sheets of donated human skin with
flashes from infrared lamps. The cream blocked up to 80 per cent of the heat
blast in ideal lab conditions, but the team expects only about 50 per cent
protection in the field.
Because the cream has to reflect only infrared light, the researchers can
colour it to turn it into camouflage make-up. Cooper has already produced a dark
brown version of the cream for the MoD to assess.
Bryan Lawton, an expert on heat transfer in skin at Cranfield University in
Shrivenham, Wiltshire, says soldiers in the field could definitely benefit from
the protective cream. 鈥淚t鈥檚 becoming more important for the military, because
the number of burns they get is going up. Soldiers are more exposed,鈥� he says.