- Spandex-or elastane-is a synthetic fiber known for its
exceptional elasticity. It is stronger and more durable than rubber, its
major non-synthetic competitor. It was invented in 1959 by DuPont
chemist Joseph Shivers. When first introduced, it revolutionized many
areas of the clothing industry.
"Spandex" is a generic name and not derived from the chemical name of
the fiber, as are most manufactured fibers, but an extension of the
word expand. "Spandex" is the preferred name in North America;
elsewhere it is referred to as "elastane".
Spandex fiber production
- Spandex fibers are produced in four different ways, including
melt extrusion, reaction spinning, solution dry spinning, and solution
wet spinning. All of these methods include the initial step of reacting
monomers to produce a prepolymer. Once the prepolymer is formed, it is
reacted further in various ways and drawn out to produce a long fiber.
The solution dry spinning method is used to produce over 90% of the
world's spandex fibers.
-
Solution dry spinning
Step 1: The first step is to produce the
prepolymer. This is done by mixing a macroglycol with a diisocyanate
monomer. The two compounds are mixed together in a reaction vessel to
produce a prepolymer. A typical ratio of glycol to diisocyanate is 1:2.
Step
2: The prepolymer is further reacted with an equal amount of
diamine. This reaction is known as chain extension reaction. The
resulting solution is diluted with a solvent to produce the spinning
solution. The solvent helps make the solution thinner and more easily
handled, and then it can be pumped into the fiber production cell.
Step
3: The spinning solution is pumped into a cylindrical spinning
cell where it is cured and converted into fibers. In this cell, the
polymer solution is forced through a metal plate called a spinneret.
This causes the solution to be aligned in strands of liquid polymer. As
the strands pass through the cell, they are heated in the presence of a
nitrogen and solvent gas. This process causes the liquid polymer to
react chemically and form solid strands.
Step 4:
As the fibers exit the cell, an amount of solid strands are bundled
together to produce the desired thickness. Each fiber of spandex is made
up of many smaller individual fibers that adhere to one another due to
the natural stickiness of their surface.
Step 5:
The resulting fibers are then treated with a finishing agent which can
be magnesium stearate or another polymer. This treatment prevents the
fibers' sticking together and aids in textile manufacture. The fibers
are then transferred through a series of rollers onto a spool.
Step
6: When the spools are filled with fiber, they are put into
final packaging and shipped to textile manufacturers