It was about 18 years into her work at DuPont that one day in her normal every day routine Kwolek where she would create another polymer, melt it, and ask a technician to turn it into a fiber with a machine called a spinneret. A spinneret takes the polymer and pushes it out in an air-stream that creates a fiber in such a way that is comparable to how cotton candy is made. The spinneret can also be compared to how a spider spins a web (Selle, 2004).
In Selle’s report, he offers Kwolek’s own words of what it was like when she first discovered it: “Ordinarily, when you have a polymer solution of a flexible polymer chain, it sort of reminds you of molasses. IT may not be as thick but is generally of a transparent or translucent nature. With the polymer solution that I had, it was almost like water – and it was cloudy” (Selle, 2004).
After she was unable to remove the trademark cloudiness of the polymer she proceeded to go through the normal process of her daily routine by bringing what she had to a technician to see if it could be wove into a fiber. When she brought it to the technician to see what it would make, the technician declined saying that, just from looking at the solution, it could not be spun. After days of relentlessly reasoning with the technician Kwolek eventually was able to persuade him to spin the fiber. After he spun it, it came out perfectly and as exactly as she had imagined. What was more, however, was that this fiber was “strong, tough, flame resistant, and stiff beyond all imagining” (Selle, 2004).
Kevlar is essentially a liquid crystal which is a state of matter that resides somewhere between a liquid and a solid. The molecules of a liquid crystal are tightly packed and creates something like a thick syrup and after enough of the polymer has been added, the solution turns watery and eventually becomes a liquid crystal solution (Selle, 2004).
Kwolek gives a perfect analogy in Selle’s report as she explains it as logs in a river:
“Increasing the viscosity of the polymer solution is like adding more logs to the river so that they jam against each other helter-skelter and clog up the channel. At some point, though, groups of logs begin to clap together and form arrays of parallel timbers until the entire river is filled by logs in parallel. This allows for them to flow freely downstream and also for many more logs to be added, since all the spaces between the logs are eliminated by the parallelism. This is akin to the solution suddenly turning watery, allowing the concentration to be increased.”
In order to make a Kevlar fiber the Kevlar crystals are put through the holes of a spinneret. Kwolek described it further as when the molecules are in the holes they are “already lined up. You solidify the fibers by removing the solvent, and you end up with a fiber where all these molecules are lined up parallel to each other. They’re highly oriented along the long fiber axis, and they’re highly crystalline” (Selle, 2004).
