Researchers at Massachusetts Institute of Technology (MIT) created a process that can produce ultrafine fibers (in nanometers) that are exceptionally strong and tough. The fibers can be used in many applications like protective armor and nanocomposites. The process is also expected to be inexpensive and easily produced.
According to Gregory Rutledge, the MIT professor of chemical engineering, and postdoc Jay Park, the new process is called gel electrospinning. Rutledge said that in materials science, there are a lot of tradeoffs. Researchers are able to enhance a specific characteristic of a material, but there will be a decline in a different characteristic. “Strength and toughness are a pair like that: Usually when you get high strength, you lose something in the toughness,” he said. “The material becomes more brittle and therefore doesn’t have the mechanism for absorbing energy, and it tends to break.” However, in this new process they created for the fibers, many of these tradeoffs are eliminated.
“It’s a big deal when you get a material that has very high strength and high toughness,” which is the case in this process. The new process uses a variation of the traditional method called gel spinning but adds electrical forces. The new process results in ultrafine fibers of polyethylene which match or exceed the properties of some of the strongest fiber materials like Kevlar and Dyneema, which are usually used in applications like bullet-stopping body armor.
“We started off with a mission to make fibers in a different size range, namely below 1 micron [millionth of a meter], because those have a variety of interesting features in their own right,” Rutledge said “And we’ve looked at such ultrafine fibers, sometimes called nanofibers, for many years. But there was nothing in what would be called the high-performance fiber range.”
High-performance fibers like Kevlar and polyethylenes that are gel-spun like Dyneema and Spectra are also used in ropes which are used for extreme activities and aas reinforcing fibers in some high-performance composites.
“There hasn’t been a whole lot new happening in that field in many years, because they have very top-performing fibers in that mechanical space,” Rutledge said. However, this new material, according to the scientists, exceeds all the others. “What really sets those apart is what we call specific modulus and specific strength, which means that on a per-weight basis they outperform just about everything.” Modulus refers to how stiff a fiber is, or how much it resists being stretched.