Nylon

For other uses, see Nylon (disambiguation). This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (September 2008) This article's introduction section may not adequately summarize its contents. To comply with Wikipedia's lead section guidelines, please consider expanding the lead to provide an accessible overview of the article's key points. (November 2010) Nylon Density 1.15 g/cm3 Electrical conductivity (σ) 10−12 S/m Thermal conductivity 0.25 W/(m·K) Melting point 463–624 K 190–350 °C 374–663 °F Nylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station. Nylon is one of the most commonly used polymers. Contents 1 Overview 2 Chemistry 2.1 Concepts of nylon production 2.2 Characteristics 3 Bulk properties 4 Historical uses 5 Use in composites 6 Hydrolysis and degradation 7 Incineration and recycling 8 Etymology 9 See also 10 References 11 Further reading 12 External links // Overview This section does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2011) Nylon is a thermoplastic silky material, first used commercially in a nylon-bristled toothbrush (1938), followed more famously by women's stockings ("nylons"; 1940). It is made of repeating units linked by amide bonds and is frequently referred to as polyamide (PA). Nylon was the first commercially successful synthetic polymer. There are two common methods of making nylon for fiber applications. In one approach, molecules with an acid (COOH) group on each end are reacted with molecules containing amine (NH2) groups on each end. The resulting nylon is named on the basis of the number of carbon atoms separating the two acid groups and the two amines. These are formed into monomers of intermediate molecular weight, which are then reacted to form long polymer chains. Nylon was intended to be a synthetic replacement for silk and substituted for it in many different products after silk became scarce during World War II. It replaced silk in military applications such as parachutes and flak vests, and was used in many types of vehicle tires. Nylon fibres are used in many applications, including fabrics, bridal veils, carpets, musical strings, and rope. Solid nylon is used for mechanical parts such as machine screws, gears and other low- to medium-stress components previously cast in metal. Engineering-grade nylon is processed by extrusion, casting, and injection molding. Solid nylon is used in hair combs. Type 6,6 Nylon 101 is the most common commercial grade of nylon, and Nylon 6 is the most common commercial grade of molded nylon. Nylon is available in glass-filled variants which increase structural and impact strength and rigidity, and molybdenum sulfide-filled variants which increase lubricity. Aramids are another type of polyamide with quite different chain structures which include aromatic groups in the main chain. Such polymers make excellent ballistic fibres. Chemistry Nylons are condensation copolymers formed by reacting equal parts of a diamine and a dicarboxylic acid, so that amides are formed at both ends of each monomer in a process analogous to polypeptide biopolymers. Chemical elements included are carbon, hydrogen, nitrogen, and oxygen. The numerical suffix specifies the numbers of carbons donated by the monomers; the diamine first and the diacid second. The most common variant is nylon 6-6 which refers to the fact that the diamine (hexamethylene diamine, IUPAC name: 1,6-diaminohexane) and the diacid (adipic acid, IUPAC name: hexane-1,6-dicarboxylic acid) each donate 6 carbons to the polymer chain. As with other regular copolymers like polyesters and polyurethanes, the "repeating unit" consists of one of each monomer, so that they alternate in the chain. Since each monomer in this copolymer has the same reactive group on both ends, the direction of the amide bond reverses between each monomer, unlike natural polyamide proteins which have overall directionality: C terminal → N terminal. In the laboratory, nylon 6-6 can also be made using adipoyl chloride instead of adipic. It is difficult to get the proportions exactly correct, and deviations can lead to chain termination at molecular weights less than a desirable 10,000 daltons (u). To overcome this problem, a crystalline, solid "nylon salt" can be formed at room temperature, using an exact 1:1 ratio of the acid and the base to neutralize each other. Heated to 285 °C (545 °F), the salt reacts to form nylon polymer. Above 20,000 daltons, it is impossible to spin the chains into yarn, so to combat this, some acetic acid is added to react with a free amine end group during polymer elongation to limit the molecular weight. In practice, and especially for 6,6, the monomers are often combined in a water solution. The water used to make the solution is evaporated under controlled conditions, and the increasing concentration of "salt" is polymerized to the final molecular weight. DuPont patented1 nylon 6,6, so in order to compete, other companies (particularly the German BASF) developed the homopolymer nylon 6, or polycaprolactam — not a condensation polymer, but formed by a ring-opening polymerization (alternatively made by polymerizing aminocaproic acid). The peptide bond within the caprolactam is broken with the exposed active groups on each side being incorporated into two new bonds as the monomer becomes part of the polymer backbone. In this case, all amide bonds lie in the same direction, but the properties of nylon 6 are sometimes indistinguishable from those of nylon 6,6 — except for melt temperature and some fiber properties in products like carpets and textiles. There is also nylon 9. The 428 °F (220 °C) melting point of nylon 6 is lower than the 509 °F (265 °C) melting point of nylon 6,6.2 Nylon 5,10, made from pentamethylene diamine and sebacic acid, was studied by Carothers even before nylon 6,6 and has superior properties, but is more expensive to make. In keeping with this naming convention, "nylon 6,12" (N-6,12) or "PA-6,12" is a copolymer of a 6C diamine and a 12C diacid. Similarly for N-5,10 N-6,11; N-10,12, etc. Other nylons include copolymerized dicarboxylic acid/diamine products that are not based upon the monomers listed above. For example, some aromatic nylons are polymerized with the addition of diacids like terephthalic acid (→ Kevlar Twaron) or isophthalic acid (→ Nomex), more commonly associated with polyesters. There are copolymers of N-6,6/N6; copolymers of N-6,6/N-6/N-12; and others. Because of the way polyamides are formed, nylon would seem to be limited to unbranched, straight chains. But "star" branched nylon can be produced by the condensation of dicarboxylic acids with polyamines having three or more amino groups. The general reaction is: A molecule of water is given off and the nylon is formed. Its properties are determined by the R and R' groups in the monomers. In nylon 6,6, R = 4C and R' = 6C alkanes, but one also has to include the two carboxyl carbons in the diacid to get the number it donates to the chain. In Kevlar, both R and R' are benzene rings. Concepts of nylon production The first approach: combining molecules with an acid (COOH) group on each end are reacted with two chemicals that contain amine (NH2) groups on each end. This process creates nylon 6,6, made of hexamethylene diamine with six carbon atoms and adipic acid. The second approach: a compound has an acid at one end and an amine at the other and is polymerized to form a chain with repeating units of (-NH-[CH2n-CO-)x. In other words, nylon 6 is made from a single six-carbon substance called caprolactam. In this equation, if n=5, then nylon 6 is the assigned name (may also be referred to as polymer). The characteristic features of nylon 6,6 include: Pleats and creases can be heat-set at higher temperatures More compact molecular structure Better weathering properties; better sunlight resistance Softer "Hand" Higher melting point (256 °C / 492.8 °F) Superior colorfastness Excellent abrasion resistance On the other hand, nylon 6 is easy to dye, more readily fades; it has a higher impact resistance, a more rapid moisture absorption, greater elasticity and elastic recovery. Characteristics Variation of luster: nylon has the ability to be very lustrous, semilustrous or dull. Durability: its high tenacity fibers are used for seatbelts, tire cords, ballistic cloth and other uses. High elongation Excellent abrasion resistance Highly resilient (nylon fabrics are heat-set) Paved the way for easy-care garments High resistance to insects, fungi, animals, as well as molds, mildew, rot and many chemicals Used in carpets and nylon stockings Melts instead of burning Used in many military applications Good specific strength Transparent under infrared light (-12dB)3 Bulk properties Above their melting temperatures, Tm, thermoplastics like nylon are amorphous solids or viscous fluids in which the chains approximate random coils. Below Tm, amorphous regions alternate with regions which are lamellar crystals.[2] The amorphous regions contribute elasticity and the crystalline regions contribute strength and rigidity. The planar amide (-CO-NH-) groups are very polar, so nylon forms multiple hydrogen bonds among adjacent strands. Because the nylon backbone is so regular and symmetrical, especially if all the amide bonds are in the trans configuration, nylons often have high crystallinity and make excellent fibers. The amount of crystallinity depends on the details of formation, as well as on the kind of nylon. Apparently it can never be quenched from a melt as a completely amorphous solid. Nylon 6,6 can have multiple parallel strands aligned with their neighboring peptide bonds at coordinated separations of exactly 6 and 4 carbons for considerable lengths, so the carbonyl oxygens and amide hydrogens can line up to form interchain hydrogen bonds repeatedly, without interruption. Nylon 5,10 can have coordinated runs of 5 and 8 carbons. Thus parallel (but not antiparallel) strands can participate in extended, unbroken, multi-chain β-pleated sheets, a strong and tough supermolecular structure similar to that found in natural silk fibroin and the β-keratins in feathers. (Proteins have only an amino acid α-carbon separating sequential -CO-NH- groups.) Nylon 6 will form uninterrupted H-bonded sheets with mixed directionalities, but the β-sheet wrinkling is somewhat different. The three-dimensional disposition of each alkane hydrocarbon chain depends on rotations about the 109.47° tetrahedral bonds of singly-bonded carbon atoms. When extruded into fibers through pores in an industrial spinneret, the individual polymer chains tend to align because of viscous flow. If subjected to cold drawing afterwards, the fibers align further, increasing their crystallinity, and the material acquires additional tensile strength.[3] In practice, nylon fibers are most often drawn using heated rolls at high speeds. Block nylon tends to be less crystalline, except near the surfaces due to shearing stresses during formation. Nylon is clear and colorless, or milky, but is easily dyed. Multistranded nylon cord and rope is slippery and tends to unravel. The ends can be melted and fused with a heat source such as a flame or electrode to prevent this. When dry, polyamide is a good electrical insulator. However, polyamide is hygroscopic. The absorption of water will change some of the material's properties such as its electrical resistance. Nylon is less absorbent than wool or cotton. Historical uses Bill Pittendreigh, DuPont, and other individuals and corporations worked diligently during the first few months of World War II to find a way to replace Asian silk and hemp with nylon 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 U.S. currency. At the outset of the war, cotton accounted for more than 80% of all fibers used and manufactured, and wool fibers accounted for the remaining 20%. By August 1945, manufactured fibers had taken a market share of 25% and cotton had dropped. Some of the terpolymers based upon nylon are used every day in packaging. Nylon has been used for meat wrappings and sausage sheaths. Use in composites Nylon can be used as the matrix material in composite materials, with reinforcing fibres like glass or carbon fiber; such a composite has a higher density than pure nylon. Such thermoplastic composites (25% glass fibre) are frequently used in car components next to the engine, such as intake manifolds, where the good heat resistance of such materials makes them feasible competitors to metals. Hydrolysis and degradation All nylons are susceptible to hydrolysis, especially by strong acids, a reaction essentially the reverse of the synthetic reaction shown above. The molecular weight of nylon products so attacked drops fast, and cracks form quickly at the affected zones. Lower members of the nylons (such as nylon 6) are affected more than higher members such as nylon 12. This means that nylon parts cannot be used in contact with sulfuric acid for example, such as the electrolyte used in lead-acid batteries. When being molded, nylon must be dried to prevent hydrolysis in the molding machine barrel since water at high temperatures can also degrade the polymer. The reaction is of the type: Incineration and recycling Various nylons break down in fire and form hazardous smoke, and toxic fumes or ash, typically containing hydrogen cyanide. Incinerating nylons to recover the high energy used to create them is usually expensive, so most nylons reach the garbage dumps, decaying very slowly.4 Some recycling is done on nylon, usually creating pellets for reuse in the industry, but this is done at a much lower scale.5 Etymology In 1940, John W. Eckelberry of DuPont stated that the letters "nyl" were arbitrary and the "on" was copied from the suffixes of other fibers such as cotton and rayon. A later publication by DuPont explained that the name was originally intended to be "No-Run" ("run" meaning "unravel"), but was modified to avoid making such an unjustified claim and to make the word sound better.6 An apocryphal tale is that Nylon is a conflation of "New York" and "London". Equally spurious is the backronym for "Now You've Lost, Old Nippon" referring to the supposed loss of demand for Japanese silk. See also Aramid Forensic engineering Polymers Plastic Nylon 6 Nylon 6-6 Ballistic Nylon Rip-stop Nylon Cordura Nylon riots Step-growth polymerization Nylon-eating bacteria References ^ History of Nylon US Patent 2,130,523 'Linear polyamides suitable for spinning into strong pliable fibers', U.S. Patent 2,130,947 'Diamine dicarboxylic acid salt' and U.S. Patent 2,130,948 'Synthetic fibers', all issued September 20, 1938 ^ Typical physical characteristics of nylon at "Basics of Design Engineering" [1] ^ Millimeter-wave, terahertz, and mid-infrared transmission through common clothing Appl. Phys. Lett. 85, 519 (2004); doi:10.1063/1.1771814 ^ Typically 80 to 100% is sent to landfill or garbage dumps, while less than 18% are incinerated while recovering the energy. See Handbook of Plastics Recycling at Google Books. ^ Typically one percent or less of nylons are recycled this way. ^ Context, vol. 7, no. 2, 1978 Further reading Textiles by Sara J. Kadolph, ISBN 0131187694 External links For historical perspectives on nylon, see the Documents List of "The Stocking Story: You Be The Historian" at the Smithsonian website, by The Lemelson Center for the Study of Invention and Innovation, National Museum of American History, Smithsonian Institution. Wikimedia Commons has media related to: Nylon A chemical demonstration of the synthesis of nylon in Carleton University's CHEM 1000 course. (Video) Typical properties of Nylon / Polyamide Polyamide material description Discussion of nylon synthesis and properties "How Nylon Yarn Is Made", January 1946, Popular Science from raw material to shipment article with drawings and illustrations v · d · eFibers Natural Animal Alpaca · Angora · Bison down · Camel hair · Cashmere · Catgut · Chiengora · Guanaco · Llama · Mohair · Pashmina · Qiviut · Rabbit · Silk · Sinew · Spider silk · Wool · Vicuña · Yak Vegetable Abacá · Bamboo · Coir · Cotton · Flax (Linen) · Hemp · Jute · Kapok · Kenaf · Piña · Raffia palm · Ramie · Sisal · Wood Mineral Asbestos · Basalt · Mineral wool · Glass wool Cellulose Acetate · Art silk · Bamboo · Lyocell (Tencel) · Modal · Rayon Synthetic Acrylic · Aramid (Twaron · Kevlar · Technora · Nomex) · Carbon (Tenax) · Derclon · Microfiber · Modacrylic · Nylon · Olefin · Polyester · Polyethylene (Dyneema · Spectra) · Spandex · Vinalon · Zylon v · d · eClothing Materials Cotton · Fur · Leather · Linen · Nylon · Polyester · Rayon · Silk · Spandex · Wool Tops Blouse · Crop top · Dress shirt · Halterneck · Henley shirt · Hoodie · Jersey · Guernsey (clothing) · Poet shirt · Polo shirt · Shirt · Sleeveless shirt · Sweater · T-shirt · Tube top · Turtleneck · Twinset Trousers or pants Bell-bottoms · Bermuda shorts · Bondage pants · Capri pants · Cargo pants · Culottes · Cycling shorts · Dress pants · Jeans · Jodhpurs · Overall · Parachute pants · Phat pants  · Shorts · Sweatpants · Windpants Skirts A-line skirt · Ballerina skirt · Fustanella · Hobble skirt · Jean skirt · Job skirt · Leather skirt · Kilt · Men's skirts · Microskirt · Miniskirt · Pencil skirt · Poodle skirt · Prairie skirt · Rah-rah skirt · Sarong · Skort · Slip · Train · Wrap Dresses Ball gown · Cocktail dress · Evening gown · Gown · Jumper dress · Little black dress · Petticoat · Sari · Sundress · Tea gown · Wedding dress Suits and uniforms Academic dress · Afrocentric suit · Black tie · Buddhist monastic robe · Clerical clothing · Court dress · Gymslip · Jumpsuit · Lab coat · Lounge suit · Mao suit · Morning dress · Pantsuit · Red Sea rig · Scrubs · Stroller · Tangzhuang · Tuxedo · White tie Outerwear Abaya · Academic gown · Anorak · Apron · Blazer · Cagoule · Cloak · Coat · Duffle coat · Duster · Frock coat · Jacket · Greatcoat · Goggle Jacket · Hoodie · Opera coat · Overcoat · Pea coat · Poncho · Raincoat · Redingote · Robe · Shawl · Shrug · Ski suit · Sleeved blanket · Top coat · Trench coat · Vest · Waistcoat · Windbreaker Underwear Boxer briefs · Boxer shorts · Brassiere · Briefs · Compression shorts · Corselet · Corset · Diaper · Knickers · Lingerie · Loincloth · Long underwear · Men's undergarments · Panties · Teddy · Temple garment · Trunks · Undershirt Accessories Ascot tie · Belly chain · Belt · Bow tie · Chaps · Coin purse · Earring · Gaiters · Gloves · Handbag · Leg warmer · Leggings · Necklace · Necktie · Scarf · Stocking · Sunglasses · Suspenders · Tights Footwear Athletic shoe · Boot · Court shoe · Dress shoe · Flip-flops · Hosiery · Plimsoll shoe · Sandal · Shoe · Slipper · Sock Headwear Balaclava · Cap · Fascinator · Gaung baung · Hat · Headband · Helmet · Hijab · Hood · Kerchief · Kippah · Mantilla · Niqāb · Sombrero · Turban · Ushanka · Veil · Šajkača Nightwear Babydoll · Blanket sleeper · Negligee · Nightcap · Nightgown · Nightshirt · Peignoir · Pajamas Swimwear Bikini · Boardshorts · Swim diaper · Wetsuit Clothing parts Back closure · Buckle · Button · Buttonhole · Collar · Cuff · Elastic · Fly · Hemline · Hook-and-eye · Lapel · Neckline · Pocket · Shoulder pad · Shoulder strap · Sleeve · Snap · Strap · Velcro · Waistline · Zipper National costume Albanian dress  · Abaya · Aboyne dress · Áo bà ba · Áo dài · Áo tứ thân · Baro't saya & Barong Tagalog · Bunad · Þjóðbúningurinn · Cheongsam (Qípáo) · Dashiki · Deel · Dhoti · Dirndl · Djellaba · Gákti · Gho & Kira · Han Chinese clothing · Hanbok · Jellabiya · Jilbāb · Kebaya · Kente cloth · Kilt · Kimono · Lederhosen · Sampot · Sarafan · Sari · Sarong · Scottish dress · Thawb Historical garments Banyan · Bedgown · Bodice · Braccae · Breeches · Breeching · Brunswick · Chemise · Cravat · Chiton · Chlamys · Doublet · Exomis · Farthingale · Frock · Himation · Hose · Houppelande · Jerkin · Justacorps · Knickerbockers · Palla · Peplos · Polonaise · Smock-frock · Stola · Toga · Tunic History and surveys Africa · Ancient Greece · Ancient Rome · Ancient world · Anglo-Saxon · Byzantine · Clothing terminology · Dress code · Early Medieval Europe · Formal wear · Han Chinese clothing · History of clothing and textiles · History of Western fashion series (1100s-2000s) · Sumptuary law · Timeline of clothing and textiles technology · Undergarments · Vietnam · Women wearing pants See also Adaptive clothing · Adult diaper · Bathrobe · Costume · Fashion · Ironing · Laundry · Locking clothing · Reversible garment