Nylon

In 1928 E. I. du Pont de Nemours & Company (Du Pont) launched one of its first basic research programs and hired Wallace Hume Carothers to run it. He was brought to Du Pont in part because his fellow researchers at Harvard University and the University of Illinois had called him the best

synthetic chemist they knew. The program he supervised was designed to investigate the composition of natural polymers such as silk, cellulose, and rubber. Many of Carothers's efforts related to condensation polymers were based on his deduction that if a monofunctional reactant reacted in a certain manner in forming a small molecule, then similar reactions that employed a comparable reactant, but with two reactive groups, would form polymers. (See Figure 1.)

The amide unit (found in polyamides) shown in Figure 2 is the same connective grouping that is found in proteins.

Although the Carothers group had worked with both polyesters and polyamides, they initially emphasized their work on the polyesters, as polyesters were more soluble and easier to work with. Julian Hill, a member of the Carothers team, noticed that he could form fibers if he separated a portion of a soft polyester material using a glass stirring rod and pulled it away from the clump. But because the polyesters had softening points that were too low for their use as textiles, the group returned to its work with the polyamides. The researchers found that fibers could also be formed from the polyamides, similar to those formed from the polyesters. The strength of these fibers approached, and in some cases surpassed, the strengths of natural fibers. This new miracle fiber (nylon) was introduced at the 1939 New York World's Fair, in an exhibit that announced the synthesis of a wonder fiber from "coal, air, and water"—an exaggeration but nevertheless eye-catching. When the nylon stockings were first offered for sale in New York City, on May 15, 1940, over four million pairs were sold in the first few hours. Nylon stocking sales took a large drop during World War II when it became publicized that nylon was needed to make parachutes.

The polyamides (nylons) were given a special naming system. Nylons made from diamines and dicarboxylic acids are designated by two numbers, the first representing the number of carbons in the diamine chain (a) and the second the number of carbons in the dicarboxylic acid (b). (See Figure 3.)

The nylon developed by Carothers at Du Pont was nylon 6,6. Because of the importance of starting out with equal amounts of the two reactants, salts of the diamine and of the diacid are made and then used in the commercial synthesis of nylon 6,6. (See Figure 4.)

STEPHANIE KWOLEK (1923–)

Stephanie Kwolek has seventeen patents, the first of which is for Kevlar. After creating a new polymer, she would spin them into fibers for strength and flexibility testing. Material for fibers of Kevlar was cloudy white instead of molasses brown, the first indication that she had uncovered an exceptional polymer.

—Valerie Borek

Nylon 6,6 (or simply nylon 66) is the largest volume nylon used as fiber, film, and plastic. About 1,134 million kilograms (2,500 million pounds) of nylon 66 were produced for fiber applications in 2000. Nylon 66 is used to make tire cord, rope, clothing, thread, hose, undergarments, rug filament,

socks, dresses, and more. Because of the presence of polar units in nylons, similar to the presence of polar units in proteins, materials made from nylon have a nice "feel" to them. Nylon materials also attract odors (many everyday odors are polar in nature) and are easily stained. Most textile and fabric products are treated to repel unwanted odors and stainmaking materials.

Nylon 66 was the first engineering thermoplastic, and up until 1953 represented all of engineering thermoplastic sales. The term "thermoplastic" denotes a material that can be melted through heating. The term "engineering thermoplastics" describes a plastic material that can be cut, drilled, or machined. About 680.4 million kilograms (1,500 million pounds) of nylons were produced in the United States in 2000 for thermoplastic use. Nylon 66 plastic is tough and rigid. It has a relatively high use temperature (to about 270°C or 518°F), and is used in the manufacture of products ranging from automotive gears to hairbrush handles. Molded nylon 66 is used to make skate wheels, motorcycle crank cases, bearings, tractor hood extensions, skis for snowmobiles, lawnmower blades, bicycle wheels, and so on.

Most polymers, when heated, progress from a glasslike solid to a softer solid, and then to a viscous "taffylike" material that is most amenable to heat-associated fabrication. In the case of nylon 66, the transition from the solid to the soft stage is abrupt, requiring that fabrication be closely watched.

The presence in nylons of polar groups results in materials that have a relatively high glass transition temperature (T_g, the point at which segmental mobility begins) and high melting point (the point at which entire polymer chain mobility begins), so that, unlike many vinyl polymers such as polyethylene and polypropylene (which must be at temperatures above their glass transition temperatures to possess needed flexibility), nylons, and many other condensation polymers, function best in contexts in which strength, and not flexibility, is the desired attribute.

Because they have these polar groups that also allow for hydrogen bonding , nylons and most condensation polymers are also stronger, more rigid and brittle, and tougher in comparison to most vinyl polymers. Nylons are also "lubrication-free," meaning they do not need lubricant for easy mobility; thus they can be used to make mechanical bearings and gears that do not need periodic lubrication.

During the early 1950s George deMestral, after walking in the Swiss countryside, noticed that he had cockleburs caught in his jacket. He examined the cockleburs and noticed that they had tiny "hooks." His cotton jacket had loops that "held" the cockleburs. He began playing with his observations and making combinations of materials—one having rigid hooks and the other having flexible loops or eyes. Today, Velcro, the name given to the nylon-based hook-and-eye combination, uses nylon as both the hook material and the eye material. Polyester is sometimes blended with the nylon to make it stronger. (Polyesters have also been used to make hook-andeye material.) Velcro is used to fasten shoes, close space suits, and it has many other applications.

Nylon 6, produced via the ring-opening reaction of the compound caprolactam is structurally similar to nylon 66 and has similar properties and uses. It is widely used in Europe in place of nylon 66, but not in the United States. (See Figure 5.)

Nylon 6,10 and nylon 6,12 are also commercially available. Because of the presence of the additional methylene (–CH₂–) groups that are hydrophobic (water-hating), these nylons are more resistant to moisture and more ductile than nylon 66.

DSM (once called Dutch State Mines) introduced nylon 4,6 (Stanyl) in 1990. It is produced via the condensation reaction between adipic acid and 1,4-diaminobutane, produced from renewable resources. Stanyl can withstand temperatures up to about 300°C (570°F), allowing it to occupy a niche position—between conventional nylons and high-performance materials. (See Figure 6.)

Several new commercial ventures are based on using natural, renewable starting materials (instead of petrochemicals). These products are known as "green" products because they are made from renewable resources and can be composted. The compound 1,4-butanediamine, used to produce nylon 4,6 from natural material, is such a green product.

In general, more crystalline nylons are fibrous whereas less crystalline nylon materials are more plastic in behavior.

Several aromatic polyamides, called aramids, have been produced. These materials are strong, are stable at high temperatures, and have good flame-resistance properties. Nomex (made from m -diaminobenzene and isophthalic acid) is used to make flame-resistant clothing and the thin pads used in space shuttles to protect sintered silica-fiber mats from stress and vibration during flight. Kevlar (made from p -diaminobenzene and terephthalic acid) is structurally similar to Nomex and by weight is stronger than steel. It is used in the manufacture of so-called bullet-resistant clothing. Because of its outstanding strength to weight ratio, it was used as the skin covering of the human-powered Gossamer Albatross, flown over the English Channel.

Aramids are also widely used as the fibers that are part of space-age composites and in the manufacture of tire cord and tread. (See Figure 7.)

see also Carothers, Wallace; Materials Science; Polymers, Synthetic.

Charles E. Carraher Jr.

Bibliography

Allcock, Harry R.; Lampe, Frederick W.; and Mark, James E. (2003). Contemporary Polymer Chemistry, 3rd edition. Upper Saddle River, NJ: Pearson/Prentice Hall.

Amato, Ivan (1997). Stuff: The Materials the World Is Made Of. New York: Basic Books.

Campbell, Ian M. (2000). Introduction to Synthetic Polymers, 2nd edition. New York: Oxford University Press.

Carraher, Charles E., Jr. (2003). Giant Molecules: Essential Materials for Everyday Living and Problem Solving, 2nd edition. Hoboken, NJ: Wiley.

Carraher, Charles E., Jr. (2003). Polymer Chemistry, 6th edition. New York: Marcel Dekker.

Collier, Billie J., and Tortora, Phyllis G. (2000). Understanding Textiles. Upper Saddle River, NJ: Prentice Hall.

Craver, Clara E., and Carraher, Charles E., Jr. (2000). Applied Polymer Science: 21st Century. New York: Elsevier.

Elias, Hans-Georg (1997). An Introduction to Polymer Science. New York: Wiley.

Morawetz, Herbert (1985). Polymers: The Origins and Growth of a Science. New York: Wiley.

Morgan, Paul W., and Kwolek, Stephanie L. (1959). "The Nylon Rope Trick." Journal of Chemical Education 36:182–184.

Rodriguez, Ferdinand (1996). Principles of Polymer Systems, 4th edition. Washington, DC: Taylor & Francis.

Salamone, Joseph C., ed. (1996). Polymeric Materials Encyclopedia. Boca Raton, FL: CRC Press.

Stevens, Malcolm P. (1990). Polymer Chemistry: An Introduction, 2nd edition. New York: Oxford University Press.

Thrower, Peter (1996). Materials in Today's World, 2nd edition. New York: McGraw-Hill.

Tonelli, Alan E. (2001). Polymers from the Inside Out: An Introduction to Macromolecules. New York: Wiley-Interscience.

NYLON

Nylon was the first fiber to be synthesized from petrochemicals and became known as the "miracle fiber." Its inventor was American chemist Wallace Carothers of the DuPont Company. Introduced in 1931, it was first called "66." By 1938 Paul Schlack, a German chemist from the I.G. Farben Company, created a different form of the fiber known as nylon 6. In 1941, British Nylon, Inc. began nylon 6 production in Great Britain. Invented two decades after rayon and acetate, nylon opened the door for synthetic fiber inventions that revolutionized the global textile industry.

DuPont began commercial production of nylon in 1939 by featuring women's hosiery at the San Francisco Exposition. It was one of the most exciting fashion innovations of the age, and women were intrigued by the strength, beauty, and low cost of nylon stockings compared to silk stockings. World War II diverted production of nylon to the war effort as it was used in products like parachutes, ponchos, tires, ropes, tents, and even U.S. currency. When commercial production resumed after World War II thousands of women lined up in New York City to purchase nylon hosiery.

Neil Armstrong planted a nylon flag on the moon in 1969 while wearing a nylon and aramid space suit, symbolizing the futuristic aura of the "miracle fiber." Synthetic fibers can be produced in various modifications. Throughout its history special-purpose nylon fibers have been developed. The Japanese company, Kuraray, began developing leather-look microfiber nylon in 1964, which is used for high-fashion apparel, sportswear, and luggage. A lustrous and luxurious-appearing Qiana nylon was introduced in the early 1970s as an innovation with the triangular cross-sectional shape of silk. It is no longer made. Antron nylon had similar properties and continues to be produced.

Consumers found nylon to be less comfortable than natural fibers. One solution was to blend nylon with other fibers to enhance strength and improve comfort. Modifications produced Hydrofil nylon, which was engineered for increased absorbency. Recent development of microfiber nylon (fibers with exceptionally fine diameters) added a comfort dimension first appreciated in active sportswear, such as athletic wear made of Tactel microfiber nylon produced by DuPont. Designer and consumer-level fashion acceptance of microfiber products continues to grow and with it may come a resurgence of nylon in apparel fashion.

Research into possible innovations for nylon continues. One frontier is micro-encapsulation in medical applications, in which nutrients and supplements encapsulated in the apparel are released as therapy to the body. Encapsulation appeared in interior textiles as perfume in furnishings used to set the mood of a room. Nylon is produced in Asia, North America, Western Europe, and Eastern Europe, with production growth showing a marked shift to Asia. Nylon's share of fiber production has decreased from 20 percent in 1982 to 11 percent in 2002. Polyester at 58 percent has clearly become the dominant synthetic fiber.

Production of nylon

Nylon is chemically synthesized from petrochemicals by reacting an acid with an amine. The variant of amine and acid determines the resultant type of nylon (e.g. 66 or 6). The compounds form a nylon salt that is dried and heated under a vacuum to eliminate water and form a polymer known as polyamide. In the technical textile literature nylon may be referred to as polyamide. The polyamide is melted, passed through a spinneret with holes, and drawn in long continuous filaments. Variations in the steps of this process allow producers to engineer specific properties. Often yarns are texturized (treated to change the surface texture) in order to add character, stretch, or bulk. Fibers are then processed into yarns relative to use.

Characteristics of nylon textiles

Nylon is known for its high strength, abrasion resistance, durability, elongation, and versatility. These properties make nylon highly suitable for heavy poplin and taffeta upholstery and luggage fabrics. The versatility of nylon allowed for creation of the aesthetics of natural fibers with far better performance. Because of excellent elongation, nylon has been particularly well suited for knitwear. Comfort has been a challenge, though, given low absorption and a medium heat retention that contribute to sweating when physically active. Hydrophil has been engineered to provide absorption and wicking (moisture transport). Nylon taffeta has been used extensively for rainwear, umbrellas, and wind-resistant garments. Static is another outcome of low moisture absorption that can be uncomfortable and possibly unsafe in some environments. Antistatic variants have been developed to manage this problem in garments and in carpeting in which finishes or small amounts of metallic and carbon fibers are used. Nylon can be heat set, making it highly resilient and shrink resistant at normal temperatures; however, at very high heat it can wrinkle, shrink, and even melt. Nylon resists damage from chemicals and is also resistant to mold, mildew, and insects. It is less resistant to damage from sunlight. Nylon attracts oil-based stains and performs best if treated with stain-release finishes. This is particularly needed for carpeting and upholstery.

Nylon in fashion across time

Introducing nylon through women's nylon hosiery created a fashion frenzy never seen for any other manufactured fiber. The momentum of this introduction made nylon the leading synthetic fiber until 1969 when polyester consumption overtook nylon. One major feature of these new textiles that had great appeal was "wash and wear," in which ironing became a seldom-or-never kind of expectation for relatively wrinkle-free textiles. Growth in popularity of knitwear, particularly sportswear, contributed to the fashionability of synthetic apparel. Yet, attempts to make nylon appealing in apparel have met with numerous comfort issues for typical clothing, leading to a perception that nylon is uncomfortable when worn. With ongoing innovations in sportswear and high fashion, nylon continues to be a fiber with a bit of "miracle" pending.

Common nylon textile uses

The primary demand for nylon is for carpeting; 80 percent of carpeting is nylon. Other interior-textile uses include bedspreads, window treatments, and upholstery. Within apparel, nylon is used in hosiery, particularly women's sheer hosiery, lingerie, foundation garments, raincoats, linings, windbreakers, and a wide array of athletic wear in which the stretch of nylon is an asset. Industrial uses are extensive and include tire cord, car headliners and trunk liners, car trims, clutch and brake pads, radiator and other hoses, car airbags, conveyer and seat belts, parachutes, racket strings, ropes and nets, sleeping bags, tarpaulins, tents, thread, fishing line, brushes, sports gear, luggage, and dental floss.

See alsoAcrylic and Modacrylic Fibers; Rayon .

bibliography

Braddock, Sarah, and Marie O'Mahony. Techno Textiles: Revolutionary Fabrics for Fashion and Design. New York: Thames and Hudson, Inc., 1998.

Collier, Billie, and Phyllis Tortora. Understanding Textiles. New York: Macmillan Publishing, 2000.

Hatch, Kathryn. Textile Science. Minneapolis: West Publishing, 1993.

Kadolph, Sara, and Anna Langford. Textiles. 9th ed. New York: Prentice-Hall, 2002.

Internet Resource

"Fibersource." American Fiber Manufacturers Association/Fiber Economics Bureau. Available from <http://www.fibersource.com>.

Carol J. Salusso

Nylon

A synthetic thermoplastic material, nylon was first introduced commercially by E.I. du Pont de Nemours and Company in the form of toothbrush bristles in 1938. The process of condensation polymerization, by which nylon and the synthetic rubber neoprene are made, was discovered by Wallace Carothers, a chemist working for the du Pont company in the 1930s. The name "nylon" itself was originally a trademark of the du Pont company, but the material is now produced in many different forms, all of which belong to the chemical group known as polyamides. Although these nylons have different characteristics and can be used in different ways, they all share the same basic qualities. In general, nylon is useful because it is a light, strong, hard-wearing material that is resistant to corrosive chemicals and can be easily molded when heated and colored with pigments. Besides these qualities, nylon is also remarkably cheap and easy to manufacture. As a result, a huge variety of different uses have been found for it, and nylon is present in almost all areas of life. For example, it appears in the form of woven fabrics, thread, and rope, as plastic sheets, moldings, and netting. Because it is resistant to wear, nylon is also used as an alternative to conventional steel bearings and gears, and as insulation in electrical equipment.

Within two years of the introduction of the first nylon toothbrushes, nylon was being spun as a multifilament yarn to make hosiery. Being harder-wearing than silk, nylon stockings were much sought after when they first appeared in 1940. This was particularly true in Europe during World War II, where gifts of nylons made American servicemen as popular with local women as Hershey chocolate made them with children. More crucially, nylon parachutes were lighter and more reliable than silk, and in military slang a parachute descent became known as a "nylon letdown." In the 1960s and 1970s nylon was at the height of its popularity as a fabric material, perhaps because of its longevity and the fact that clothes made from colored nylon do not fade with washing. Because of their tendency to generate static electricity, however, nylon fabrics are not always comfortable to wear, and as dye and detergent technologies have improved, nylon's popularity has decreased. In the 1990s nylon fabrics were most often found in waterproof outer clothing and hosiery. The material also had an effect on modern healthcare, since nylon surgical sutures, splints, braces, and many other medical items, are cheap, and easy to sterilize and keep clean.

The versatility of nylon as a material means that, besides the multifilament yarns used in clothing and the monofilaments used as bristles, nylon can also be moulded into solid objects of many different sizes and shapes. Because of its resilience, nylon is a good material for making objects that need to resist wear and tear, such as plastic containers, stationery items, floor coverings, and bearings. Nylon bearings are particularly useful under extreme conditions, where lubrication is impractical or where the bearing is exposed to water. It can also be formed into objects that hold pressure, such as bicycle tires, inflated balls, certain pump cylinders, and valves. The invention of nylon, and the plastics technologies that followed, made possible the cheap mass production of high quality consumer objects, from children's toys and kitchen utensils to computers, cameras, televisions, and sound systems.

Despite his remarkable discovery, and despite receiving over 50 other patents, the inventor of nylon, Wallace Carothers, was an unhappy man, suffering from severe depression and alcoholism. Although nylon revolutionized life in the late twentieth century, Carothers did not live to enjoy the benefits of his work. He committed suicide in 1937, not long before those first bristles went into production.

—Chris Routledge

Further Reading:

Hermes, Matthew E. Enough for One Lifetime: Wallace Carothers, Inventor of Nylon. History of Modern Chemical Sciences Series. Washington, D.C., American Chemical Society, 1996.

Kohan, Melvin I. The Nylon Plastics Handbook. Cincinnati, Hanser and Gardner, 1995.

Nylon

Wallace Carothers (1896–1937) invented nylon while working for the DuPont Company in the 1930s. The name "nylon" was originally a DuPont trademark. Nylon first appeared in the form of toothbrush bristles in 1938. Soon nylon became one of the most widely used man-made materials. It is used in ropes, plastic sheeting, netting, moldings, and woven fabrics. It is also used as an insulating material in electrical goods. Nylon takes the place of steel bearings, gears, and bushings (insulating linings for holes or tubes) in all kinds of machines. It is also widely used in medicine for making splints, sutures, braces and other items. At the start of the twenty-first century, nylon appears in almost all areas of life. Without it, many of the things people take for granted would not exist.

Within two years of the first toothbrush bristles, nylon was being used to make lightweight fabrics for hosiery. Because they were so strong, nylon stockings (see entry under 1930s—Fashion in volume 2) were more popular than silk and soon became known as nylons. Nylon also replaced silk in parachutes, and in military slang a parachute jump was known as a "nylon let-down." By the 1960s, nylon was widely used in objects from furniture to clothing. Occasionally, nylon has not always improved people's lives. In the 1970s, synthetics such as nylon dominated fashion. Like its cousin polyester (see entry under 1970s—Fashion in volume 4), nylon tended to encourage sweating. In extreme cases, nylon shirts became charged with static electricity and made the wearer's hair stand on end. Thankfully, nylon is currently most popularly used in sports wear and hosiery.

Nevertheless, nylon is not far from being the wonder material it was once thought to be. Because it is so tough and resistant to wear and tear, it is ideal for floor coverings, tires, inflated balls, pumps, valves, containers, and car body parts. The invention of nylon made possible the cheap mass production of high-quality consumer goods from children's toys to computers and sound systems. Wallace Carothers' invention revolutionized life in the twentieth century and beyond.

—Chris Routledge

For More Information

Handley, Susannah. Nylon: The Story of a Fashion Revolution: From Art Silk to Nylon and Thinking Fibres. Baltimore: Johns Hopkins University Press, 2000.

Hermes, Matthew E. Enough For One Lifetime: Wallace Carothers, Inventor of Nylon. Washington, DC: American Chemical Society, 1996.

ny·lon / ˈnīˌlän/ • n. a tough, lightweight, elastic synthetic polymer with a proteinlike chemical structure, able to be produced as filaments, sheets, or molded objects. ∎  fabric or yarn made from nylon fibers. ∎  (nylons) stockings or hose made of nylon.