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Nylon

Nylon
Density 1150 kg/m3
Electrical conductivity(σ) 10-12 (mĚohm)-1
Thermal conductivity 0.25 W/(mĚK)

This article covers the material nylon. For the women's magazine, see Nylon (magazine).

Nylon is a synthetic polymer, a plastic, invented on February 28, 1935 by Wallace Carothers at DuPont of Wilmington, Delaware, USA. The material was announced in 1938 and the first nylon products; a nylon bristle toothbrush made with nylon yarn (went on sale on February 24, 1938) and more famously, women's stockings (went on sale on May 15, 1940). Nylon fibres are now used to make many synthetic fabrics, and solid nylon is used as an engineering material.


Chemically, nylon is a condensation polymer made of repeating units with amide linkages between them: hence it is frequently referred to as a polyamide. It was the first synthetic fibre to be made entirely from inorganic ingredients: coal, water and air (and, by this, I assume the author means "inorganic" as "not from a living thing", since coal does contain carbon). These are formed into two intermediate chemicals, most commonly hexamethylene diamine and adipic acid (a dicarboxylic acid), which are then mixed to polymerise. The most common variant is nylon 6,6, also called nylon 66, which refers to the fact that both the diamine (hexamethylene diamine ) and the diacid (adipic acid) have 6 carbon backbones. The diacid and diamine units alternate in the polymer chain. Therefore, unlike natural polyamides like proteins, the direction of the amide bond reverses at each bond.

The general information above is fairly close to what goes into PA/Nylon polymerization. However, "coal and steam" is a bit simplistic, and the combination of HMD and AA to make PA-66 leaves out quite a bit of details. In fact, you CAN get PA-66 from other starting monomers. And you CAN (and always do) get any polyamide from anything other than coal.

Another common nylon is nylon 6 or polycaprolactam. It is special because it's not strictly a condensation polymer. The polymer contains all the atoms of the monomer caprolactam.

In most non-US locations (and, indeed, in the US and Europe), "nylon" polymers are known as polyamides (or PA), which is a more correct nomenclature, though still somewhat flawed. There are several different versions of these "nylons", which include various polyamides made using mono- or diacid and mono- or diamine monomers. The numbers usually appended to the "nylon" or "PA" part refer to the number of CH "units" between the reactive ends of the monomer. In the case of "Nylon 6,6", there are 6 CH units between the reactive dicarboxylic acid and 6 CH units between diamine linkages. In the case of "Nylon 6", there are 6 CH units between the reactive carboxylic acid and amine linkages (which were orginally located on the same monomer, caprolactam). Likewise, "Nylon 6,12" or "PA-6,12" consists of a polymer based upon a 6-CH diamine, and a 12-CH diacid. You can extrapolate from this to N-6,11; N-10,12; and whatnot.

Other "nylons" or "polyamides" include copolymerized carboxylic acid/diamine products that are NOT based upon the monomers listed above. For example, some "nylon" polymers are polymerized with the addition of diacids like terephthalic acid or isophthalic acid (more commonly associated with polyesters); copolymers of N66/N6; copolymers of N66/N6/N12; and others.

Oddly enough, some of the terpolymers based upon nylon are used every day in packaging. In fact, one use of nylon polymers is in meat wrappings. This usage includes some sausage/meat sheaths.

There is no evidence for the popular belief that "nylon" is a contraction of "NY" (for "New York") and "Lon" for "London", the two cities where the material was first manufactured. In 1940 John W. Eckelberry of DuPont stated that the letters "nyl" were arbitrary and the "on" was copied from the names of other fibres such as cotton and rayon. A later publication by DuPont (Context, vol. 7, no. 2, 1978) explained that the name was originally intended to be "No-Run" ("run" in this context meaning "unravel"), but was then modified to avoid making such an unjustified claim and to make it sound better. The story goes that Carothers changed one letter at a time until DuPont's management were satisfied.

Another popular belief is that nylon stands for "now you, lazy old nippon," as nylon was developed in the 1930s. In this sentence nippon stands for Japan, as in the 1930s, the decade in which nylon was developed, a chemical "war" was taking place between the US and Japan.

Even though the word nylon was coined, it was never trademarked.

During World War II, nylon replaced Asian silk in parachutes. It was also used to make tires, tents, ropes, ponchos, and other military supplies. It was even used in the production of a high-grade paper for US currency. At the outset of the War, cotton accounted for more than 80 percent of all fibres used, and manufactured and wool fibres accounted for the remaining 20 percent. By August, 1945, manufactured fibres had risen to 25 percent, and cotton had dropped to 75 percent.

Some conspiracy theorists surmise that cannabis was made illegal because the fibres from the hemp plant, used for fabrics and ropes, were in strong competition with nylon. However, nylon fiber is more than twice as strong as hemp fiber and weighs 25% less. While hemp was originally used in climbing rope, it is now virtually unused in modern climbing, including countries where cannabis is legal.

Uses

See also

Last updated: 10-24-2005 06:43:01
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