Nylon

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{|style="border: 1px solid; float: right; width: 250px;"!colspan="2" style="text-align: center; background: #CCC;"| Nylon|-|Density/[cm³ (σ)|10-12 [siemens (unit)/Metre|-|Thermal conductivity/(m·[Kelvin)|-style="background-color: #EEE;"|Melting point-624 [Kelvin
190°Celsius-350°Celsius
374°Fahrenheit-663°Fahrenheit|}

Plastic#Nylon is a generic designation for a family of synthetic polymers first produced on February 28, 1935 by Wallace Carothers at DuPont. Nylon is one of the most common polymers used as a fiber.

Overview Nylon is a thermoplastic silky material, first used commercially in a nylon-bristled toothbrush (1938), followed more famously by women's “nylons” stockings (1940). It is made of polymer linked by peptide bonds (another name for amide chemical bond) and is frequently referred to as polyamide (PA). Nylon was the first commerce successful polymer and the first chemical synthesis fiber to be made entirely from coal, water and air. These are formed into monomers of intermediate molecular mass, which are then reacted to form long polymer chains. It was intended to be a synthetic replacement for silk and substituted for it in many different products after silk became hard to come by during World War II.

Nylon replaced Silk in military applications such as parachutes and flak vests. Nylon is also a critical component in many types of vehicle tires and during the war became the replacement material for women's stockings. Nylon fibers are now used in textiless, bridal veils, carpets, guitar strings and rope. Solid nylon is also used to machine various parts such as gears and other low to medium stress components that previously were made from cast metals. Engineering grade Nylon is processed by extrusion, casting & injection molding. Type 6/6 Nylon 101 is the most common commercial grade of Nylon, and Nylon 6 is the most common commercial grade of cast Nylon. Nylon is also available in glass filled and molybdenum filled variants which increase the structural and impact strength of the material as well as it's rigidity.

Chemistry Nylons are condensation polymer formed by reacting equal parts of a amine and a dicarboxylic acid, so that peptide bonds form at both ends of each monomer in a process analogous to polypeptide biopolymers. 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) and the diacid (adipic 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 chemical reaction on both ends, the direction of the peptide bond reverses between each monomer, unlike natural polyamide proteins which have overall directionality: carboxyl → amino. In the laboratory, nylon 6,6 can also be made using adipoyl chloride instead of adipicIt is difficult to get the proportions exactly correct, and deviations can lead to chain termination at molecular weights less than a desirable 10,000 atomic mass unit (unified atomic mass unit). 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 (chemistry) to neutralize each other. Heated to 285 °C, 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 patented 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 20 September 1938 nylon 6,6, so in order to compete, other companies (particularly the German BASF) developed the homopolymer nylon 6, or caprolactam — 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 chemical reaction 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 (N6 is lower) and some fiber properties in products like carpets and textiles. There is also nylon 9.

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) 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 (molecule) 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' = 6C and R = 4C 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 benzenerings.

Nylon Fiber The Federal Trade Commissions' Definition for Nylon Fiber: A manufactured fiber in which the fiber forming substance is a long-chain synthetic polyamide in which less than 85% of the amide-linkages are attached directly (-CO-NH-) to two aliphatic groups.

A synthetic thermoplastic fiber (Nylon melts/glazes easily at relatively low temperatures)
Round, smooth, and shiny Fiber
cross sections can be either

trilobal to imitate silk
multilobal to increase staple like appearance and hand

It's most widely used structures are multifilament, monofilament, staple or tow and is available as partially drawn or as finished filaments.
Regular nylon has a round cross section and is perfectly uniform. The filaments are generally completely transparent unless they have been delustered or solution dyed. Thus, they are microscopically recognized as glass rods.
Molecular chains of nylon are long and straight variations but have no side chains or linkages.

Cold drawing (step 18 on the model) can align the chains so they are oriented with the lengthwise direction and are highly crystalline.

Nylon is related chemically to the protein fibers silk and wool.

They both have similar dye sites but nylon has many fewer dye sites than wool.

Basic 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 acidipic acid, as well as six carbon atoms.

The second approach: a compound has an acid at one end and an amine at the other and is polymerized to for a chain with repeating units of(-NH-n-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)

Nylon 6,6

Pleats and creases can be heat-set at higher temperatures

Difficult to dye

Nylon 6

Better dye Affinity

Softer Hand

Greater elasticity and elastic recovery

Better weathering properties; better sunlight resistance

Full Nylon Production Model

ProducersThe producers of nylon include: Honeywell Nylon Inc., Invista, Wellman Inc. among many others. The Dupont Company, is the most famous pioneer of the nylon we know today. The companies above now produce the nylon used in our everyday lives.

Characteristics

Variation of luster: nylon has the ability to be very lusterous, semilusterous 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 and fungi
molds, mildew, rot
many chemicals

Used in carpets and nylon stockings
Melts instead of burns
Used in many military applications

Bulk properties Above their glass transition temperature, 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 lamellae (materials) crystals. The amorphous regions contribute elasticity and the crystalline regions contribute strength and rigidity. The planar amide (-CO-NH-) groups are very chemical polarity, 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 geometric isomerism, 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 beta sheet, a strong and tough supermolecular structure similar to that found in natural keratin#Molecular biology and biochemistry and the keratin in feathers. (Proteins have only an amino acid α-carbon separating sequential -CO-NH- groups.) Nylon 6 will form uninterrupted hydrogen bond sheets with mixed directionalities, but the β-sheet wrinkling is somewhat different. The three-dimensional disposition of each alkane hydrocarbon Chain (sequence) depends on rotations about the 109.47° alkane#Molecular geometry bonds of singly-bonded carbon atoms.

When extrusion into fibers through pores in an industry spinneret, the individual polymer chains tend to align because of viscosity rheology. If subjected to cold drawing afterwards, the fibers align further, increasing their crystallinity, and the material acquires additional tensile strength. 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 stress (physics) 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.

There are carbon fiber/nylon composite material with higher density than pure nylon.

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 absorbant 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 with nylon in parachutes. It was also used to make tires, tents, ropes, ponchos, and other armed forces supplies. It was even used in the production of a high-grade paper for United States 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.

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 (Context, vol. 7, no. 2, 1978) 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. The story goes that Carothers changed one letter at a time until DuPont's management was satisfied. But he was not involved in the nylon project during the last year of his life, and committed suicide before the name was coined.

Two theories about the origin of the name claim that it is an acronym of "Now you've lost, Old Nippon" (N.Y.L.O.N.), or that it stands for "New York City-London". In the latter case, it is claimed that these were the two cities where the product was researched and developed, or that the inspiration came from a New York to London airplane ticket. There is no evidence for the 'airline ticket' theory, though some compelling evidence of the latter from contemporary researchers at Oxford University who assisted in development...Oxford can be viewed as London from New York, but Nylox would have been more accurate.

Uses

carpet fiber
clothing
fishing lines
footwear
nylon fiber
pantyhose
toothbrush bristles
velcro
airbag fiber
automobile parts: intake manifold (automotive engineering), gasoline (petrol) tanks
slings and rope used in climbing gear
machine parts, such as gears and bearing (mechanical)s
parachutes
metallized nylon balloons
classical guitar and flamenco guitar strings
paintball marker bolts
racquetball, squash (sport), and tennis racquet vibrating string
Strings (music) for String instruments
Drumstick heads
As filter media in sterlizing grade filters
Flexible tubing
Basketball netting