If wood is the world's most
versatile natural material, nylon is probably the most
useful synthetic one. It's a plastic that can be molded into everyday products
or drawn into fibers for making fabrics—and its launch in the late 1930s truly changed the world.
Don't believe me? Let me explain. You can pretty much live your entire life with nylon by your side.
You can snooze away on brushed nylon sheets until
your alarm clock (powered by nylon gears) wakes you up.
Hop across the nylon rug or carpet to your kitchen, maybe eat your breakfast from a nylon
bowl, before cleaning your teeth with a nylon toothbrush.
Hold a nylon umbrella over your head to keep out the rain when you set out for work or school or,
if the sun's shining and you're heading to the beach, wear your quick-drying nylon-based swimming shorts
instead. Feeling adventurous? You could try jumping from an airplane
and have a nylon parachute bring you safely to the ground!
Those are just a few of the things that nylon does for us every single day. What makes this material so amazing? Let's take a closer look!
Photo: Above: The world was introduced to nylon in 1938 when the DuPont chemical company used the material to make
synthetic toothbrushes. Below: You can make nylon bristles pretty much any length. This amazing citrus fruit harvesting machine has nylon filaments that are about 3.5m (~12ft) long. They spin around and shake the fruit gently from the trees. Photo by Keith Weller courtesy of US Department of Agriculture/Agricultural Research Service (USDA/ARS).
Nylon is a polymer—a plastic with super-long,
heavy molecules built up of short, endlessly repeating sections of atoms, just like a
heavy metal chain is made of ever-repeating links. Nylon is not actually one, single substance but the name
given to a whole family of very similar materials called polyamides.
So whenever we say "nylon is..." it's generally more correct to say "nylons are..."
One reason there's a family of nylons is because the original and most common form of the
material, nylon 6,6, was patented by E.I. du Pont de Nemours &
Company (DuPont™), the US firm where it was invented, so rivals such as German chemical giant
BASF had to come up with alternatives. Another
reason is that the different kinds of nylon have different
properties, which makes them useful for different things. Other kinds
of nylon include nylon 6, nylon 6,12, and nylon 5,10. Two other
"fantastic plastics" made by DuPont, Kevlar® (a superstrong
material used in bulletproof vests) and Nomex® (a fireproof textile
used in racing car suits and oven gloves), are also polyamides and they're chemically related to nylon.
Photo: Nylon couldn't wait to became a space-age material. In 1952, NASA rocket scientist
Wernher von Braun proposed building a space station out of flexible nylon, which could be carried into space by a relatively small rocket and then inflated like a car tire. That concept never made it off the ground, but nylon still played its part in space history: the flag planted on the Moon by Neil Armstrong in 1969 was made from—guess what—nylon! Illustration by Chesley Bonestell courtesy of
NASA Marshall Space Flight Center (NASA-MSFC).
How is nylon manufactured?
Unlike traditional materials such as wood,
iron, wool, and cotton, nylon does not exist
in nature: we have to make it in chemical plants from organic
(carbon-based) chemicals found in natural materials such as coal or petroleum.
(It's also possible to make nylon from renewable materials; Zytel®, a type of nylon
produced by DuPont, comes from castor oil—so, essentially, vegetables.)
The nylon polymer is made by reacting together two fairly large molecules using moderate heat (roughly
285°C or 545°F) and pressure in a reaction vessel called an
autoclave, which is a bit like an industrial-strength kettle.
One of the starting molecules is called hexane-1,6-dicarboxylic acid
(also called adipic acid) and the other is known as 1,6-diaminohexane
(also called hexamethylenediamine). When they combine, they fuse
together to make an even larger molecule and give off water in a
chemical reaction known as condensation polymerization
(condensation because water is eliminated; polymerization
because a big, repeating molecule is produced). The large polymer
formed in this case is the most common type of nylon—known as
nylon-6,6 because the two molecules from which it's made each
contain six carbon atoms; other nylons are made by reacting different starting chemicals. Usually this
chemical process produces a giant sheet or ribbon of nylon that is
shredded into chips, which become the raw material for all kinds of
everyday plastic products.
Artwork: How nylon 6,6 is made by condensation polymerization. 1) The two ingredients are 1,6-diaminohexane (left, red) and hexane-1,6-dicarboxylic acid (right, black). 2) A hydrogen (H) from the (red) diaminohexane joins with a hydroxide (OH) from the (black) acid. 3) A water molecule (blue) is lost (which is why the process is called condensation) as the two molecules join together. 4) The same thing happens over and over again, making a bigger and bigger molecule from the same repeated components—the process we call polymerization.
Nylon clothes and similar products are made not from chips but from fibers of nylon,
which are effectively strands of plastic yarn. They're made by
melting nylon chips and drawing them through a spinneret,
which is a wheel or plate with lots of tiny holes in it. Fibers of
different length and thickness are made by using holes of different
size and drawing them out at different speeds. Strands are sometimes
used by themselves (for example, in the manufacture of stockings) and
sometimes tens, hundreds, or even thousands are wrapped together to
make thicker and stronger yarns (similar to cotton but far stronger).
Photo: Strong and lightweight: clothes aren't the only things made from nylon fabrics. Parachutes were originally made from silk; now they're more likely to be made from "ripstop" nylons. This parachute was designed to help the Mars Science Laboratory make a safe landing and
is mostly nylon, with a small amount of polyester near the central vent. Photo courtesy of NASA/JPL-Caltech.
Photo: A closeup of the criss-cross reinforcement in ripstop nylon. These little rectangles are designed to stop rips or punctures from spreading, so a tiny tear won't get bigger by racing through the whole material.
How strong is nylon?
Photo: A box of 15-denier women's tights. You might take the "denier" to be an indication of strength, durability, opaqueness, coarseness, or thickness, but it's actually a measurement of thread weight.
If you've ever bought nylon tights or stockings, you'll know they're labeled
in confusing units called deniers, which is defined as the weight in grams of 9000 meters of the yarn from which they're made. Loosely speaking, for people who wear nylon garments, the denier is a "proxy" measurement of strength, durability, and wear resistance, because stockings and other things made from thicker and heavier yarns tend to be stronger and last longer than finer ones.
Denier is also related to the size of the nylon fibers from which a garment is made: the thinner the fibers, the lower the denier. Higher-denier fabrics tend to be coarser and more opaque (harder to see through).
Confused? Perhaps you've seen stockings for sale marked as "15 denier" or "40 denier" without ever really understanding what that means. If you see stockings described as 40-denier, it means a 9-km (roughly 6-mile) roll of the yarn they're made from would weigh just 40 grams (1.4 oz)—which gives you some idea just
how fine nylon yarn really is! Tights and stockings with higher denier measurements are generally thicker and stronger; ones with lower denier measurements are more sheer and more fragile. Ultra-sheer tights, for example, are usually less than 10 denier; thick winter tights can be 100 denier or more.
Scientists are much stricter about all this: the denier isn't a measurement of strength, durability, or thickness at all. To measure thread strength, we'd need to use more carefully defined units, such as grams (force) per denier, technically referred to as the tenacity (effectively the breaking strength of a fiber and equivalent
to measurements like kilograms per square centimeter or pounds per square inch for conventional
To give you an idea how strong nylon is, here's a chart of the ultimate tensile strength (again, loosely, the breaking strength) of some everyday materials. You can see that nylon is much stronger than you might think, but nowhere near as strong as metals like aluminum or steel.
Chart: Nylon is stronger than most forms of concrete and plastics such as polypropylene, but weaker than most woods and metals.
Properties of nylon
Photo: These shorts are made from 70 percent cotton and 30 percent nylon, which means they're very soft and comfortable and dry much faster than 100 percent cotton shorts. Even so, both cotton and nylon absorb water, so these aren't the most practical fabrics for swim shorts; you'll find most swimwear is 100 percent polyester because it's much
Generally, nylon is a silky smooth thermoplastic (which means it melts and turns
runny when you heat it up, generally at around 260°C or 500°F) that's
strong, tough, and durable (it's reasonably wear-proof and resists
sunlight and weathering). Since it's a synthetic plastic, it's highly
resistant to attack from such natural nasties as molds, insects, and fungi.
It's waterproof (hence its use in umbrellas and waterproof clothes)
and fast-drying because (unlike with natural fabrics like cotton or
wool) water molecules can't easily penetrate the outer surface.
It does, however, absorb a certain amount of water, so it's
less popular in swimwear than faster-drying synthetics such as polyester.
Although reasonably resistant to quite a lot of everyday substances,
nylon will dissolve in phenol, acids, and some other harsh chemicals.
Uses of nylon
It's almost easier to say what nylon isn't used for. Look around your home and
you'll find it's packed with nylon. The first products made with this
amazingly versatile chemical were toothbrushes and women's stockings.
Later it was used in everything from tennis rackets and parachutes to
inexpensive machine gears, fishing lines, and nylon rugs. Some cars
even have body parts made from nylon!
Nylon isn't always used alone. In clothes, for example, it's often blended with natural textiles such as cotton,
viscose (also known as rayon, a halfway-house, semi-synthetic made from trees and other plants), or other totally synthetic materials, including stretchy Spandex (also known as Lycra and Elastane) and quick-drying, easy-to-dye polyester.
Everyone's heard of nylon, but hardly anyone outside the world of chemistry knows the
name of Wallace Carothers (1896–1937), its brilliant, enigmatic, and
ultimately tragic inventor. Carothers was a promising academic
chemist working at Harvard University when DuPont™ lured him to its
Wilmington, Delaware headquarters in the late 1920s. His job was leading a
research team that was experimenting with polymerization and he
scored an early success with the invention of neoprene, a
synthetic rubber now best known for its use in wetsuits.
In spring 1930, one of the Carothers team,
Julian Hill, accidentally produced a
strange gooey blob of material that he could draw out into long, thin
fibers. After further research and development, this material
became nylon 6,6—the world's first commercially successful
synthetic polymer—and DuPont patented it a few years later. This should have
been a triumph for Carothers, but he'd been plagued by alcoholism and
depression for some time and personal problems had ground him down. Tragically,
he found life unbearable and committed suicide in a Philadelphia hotel in 1937.
The year after his death, DuPont launched nylon commercially, initially
in plastic toothbrushes. Two years later, in 1940, the new material caused
an incredible sensation when the first nylon stockings went on sale—something like 5 million
pairs were sold on the first day alone!
In his nine years at DuPont, Wallace Carothers filed over 50 patents,
but doubt about the value of his work was one of several factors that
had apparently driven him to his death. If only he'd known how important his
work was about to become. Today, he is rightly regarded as a pioneer
of synthetic materials and considered one of the most important chemists of modern times.
[PDF] Synthetic Fiber Manufacturing by Charles B. Weinberger, Dept of Chemical Engineering, Drexel University. August 30, 1996. A good overview of fiber-production techniques for an undergraduate audience. It covers synthetic fibers such as nylon and polyester, as well as things like fiber-optic cables. [Archived via the Wayback Machine.]
↑ For an explanation of tensile strength, density, and tenacity, and how they relate to one another, see "Properties of Fibers" in Survey of industrial chemistry by Philip J. Chenier, Springer, 2002, p.318.
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