T-shirts available at Wal-Mart could be converted into wearable armor, according to scientists from South Carolina, Switzerland and China.
By combining the carbon in the cotton with boron, the scientists have created a tough, lightweight fabric of boron carbide, the same material used to protect tanks. The research could lead to more comfortable body armor for soldiers and police. It could even be used to produce lightweight, fuel-efficient cars and aircraft.
"The current boron carbide armor is strong, but its not flexible and its very heavy," said Xiaodong Li, a scientist at the University of South Carolina and co-author of a recent article in the journal Advanced Materials. "We tried to solve this problem but with a different approach. In our approach, we used cotton T-shirts."
Boron carbide is the third hardest material on Earth, after diamond and another boron-based material. In bulletproof vests and tanks, thick, heavy ceramic plates of dark gray boron carbide protect soldiers and police.
Cotton, however, couldn't be more different from boron carbide. Soft and breathable, cotton clothes are cheap and widely worn.
The trick for the scientists was combining dissolved boron with the carbon fibers inside the cotton fibers to form boron carbide.
The scientists started with a $5 package of plain, white T-shirts purchased at Wal-Mart, which they then cut into thin strips. They dipped those white cotton strips into a black solution of boron. After an hour, the strips were removed from the solution and baked in at oven at more than 1,000 degrees Celsius (1832 degrees Fahrenheit) for an hour. The heat stripped away anything that wasn't carbon or boron, and combined these two elements into boron carbide.
The resulting fabric is very different than the original materials that at the start of the process. It's lighter, stronger, tougher and stiffer than the original cotton, but it can still be bent, unlike normal boron carbide armor plates. The physical properties of the new fabric are still being tested, said Li, but "from our preliminary results we can say the test have been very, very promising."
"We expect that the nanowires can capture a bullet," said Li.
The former T-shirt can also block other hazards as well, such as cancer-causing ultraviolet light from the sun and even life-threatening neutrons emitted by decaying radioactive materials, said Li.
Body armor is just one potential application of the new research. Covering cars or aircraft with cotton-based boron carbide, instead of the metal used today, would make these vehicles significantly lighter and more fuel efficient.
The number of potential applications is enormous, said Nicholas Kotov, a scientist at the University of Michigan who also works on developing new materials for body armor.
"In bulk the layers of this material are quite strong," said Kotov. "It's a great project and is very interesting and dynamic research direction."
