Move over Kevlar? New nanofibers combine extreme strength and toughness
Ultra-strong fibers like Dyneema and Kevlar may be in for some competition. Scientists at MIT have developed new polyethylene nanofibers that are both strong and tough, and that could someday be used in applications such as less-bulky body armor.
Led by Prof. Gregory Rutledge, the researchers created the fibers by adapting an existing technique known as gel spinning, in which a polymer gel is extruded through a heated syringe and mechanically spun into strands. In this case, however, the gel was spun not by mechanical means, but via an electrical field.
The resulting gel-electrospun nanofibers are just a few hundred nanometers (billionths of a meter) in width, and for reasons that still aren't entirely understood, they exhibit both high strength and toughness – something that doesn't occur often with materials.
"Usually when you get high strength, you lose something in the toughness," says Rutledge. "The material becomes more brittle and therefore doesn't have the mechanism for absorbing energy, and it tends to break. It's a big deal when you get a material that has very high strength and high toughness."
As compared to carbon and ceramic fibers, the new nanofibers are similar in strength but are considerably tougher. They're also less dense, which means that they outperform traditional materials on a pound-for-pound basis. Their modulus (resistance to stretching) isn't quite as good, but they should be relatively easy and inexpensive to manufacture.