Traditionally, carbon fibers are made by “carbonizing” a polymer called poly-acrylonitrile, or PAN. First, the polymer is spun into a fiber and then it is heated to very high temperatures. This causes the polymer molecules to to be converted into a homogenous carbon structure, causing the material to become a stiff solid.
Some research groups are designing new fibers that are made with 100 percent carbon nanotubes, which are among the strongest materials out there. But they’re extremely expensive. Marilyn Minus’ goal is to design a composite fiber that is twice as strong as current commercial materials, but cheaper.
To do so, she’s adding small amounts of nanotubes to the polymer fibers. The tubes, she says, act as needle-like skates allowing the long, flexible polymer chains to slide into a more ordered conformation. Now the spaghetti strands aren’t jumbled in a messy pile, but are neatly aligned, one strand evenly stacked atop the next. The alignment affords much stronger properties, says Minus.
She’s playing around with several different types of polymers and nanomaterials and varying the concentrations of each. Ultimately she hopes to have a library of sorts, with a variety of materials designed for a variety of applications. Also, because she’s using textile grade polymers with only a small percentage of nanomaterials, the prices of her fibers may not be much higher than a silk shirt.
And speaking of silk, Minus has already developed fibers that are stronger than spider silk — one of the strongest natural materials around. At the same time, her fibers are pushing the limits of Zylon, the strongest synthetic material currently available. Still at the beginning of her research, Minus believes there is still a lot room for improvement.