Once nylon polymer had been made, it still had to be spun into fibers. Learning how to spin
nylon polymer
brought a whole new crop of headaches to be overcome. The first stemmed from nylon's high
melting point. Nylon 6-6 melts at about 265 oC. To spin it
into fibers one had to heat it up to 285 oC.
All the
spinning machinery DuPont had was made for spinning rayon. Rayon is spun at low
temperature and pressure. Rayon-spinning pumps weren't designed to handle the kind of
punishment involved in spinning nylon. New pumps had to be made from a special steel alloy
known as "Ohio air die".
There was yet another problem involved with the high temperatures used in spinning nylon
polymer. At these high temperatures, gas bubbles formed in the nylon melt. To get rid of the
gas bubbles, the melt in the spinning machine had to be placed under high pressure. How high?
Nylon melt was pumped through the
spinnerets
at up to 5000 pounds per square inch! At this pressure, the gas bubbles were compressed into
solution with the nylon melt before it flowed through the spinneret.
2. Labovsky, Joseph. Oral history by John K. Smith, 24 July 1996. Philadelphia: Chemical
Heritage Foundation.
During the first experimental stages (1934-5),
polymers
were spun into fibers using machines like
the one shown in the photograph on the right. Of course, when production was scaled up,
more sophisticated equipment
had to be developed. Learning how to make nylon fibers of consistent quality on a large scale
presented a host of problems for DuPont's scientists and engineers to overcome.
High temperatures and pressures melt rayon pumps
Gas bubbles in melt
The big picture
To get an idea of how the whole spinning process took place, take a look at the diagram on the
right. Nylon polymer chips (shown in maroon) were placed in the hopper at the top, then heated
to 285 oC under a pure nitrogen atmosphere to prevent oxidation. The heat melted the
nylon chips. The nylon melt was then pumped down through the spinneret to produce filaments,
which were then collected on the windup bobbin. As you can see in the diagram, the entire
apparatus occupied three floors of a building.
References
1. Hermes, Matthew. Enough for One Lifetime: Wallace Carothers, Inventor of Nylon.
Washington, D.C.: American Chemical Society; Philadelphia: Chemical Heritage Foundation, 1996.
Photo credit
First nitrogen gas pressure spinner and windup - gift of Joe Labovsky.