History
Wallace Carothers
DuPont and the invention of Nylon
DuPont, founded by Éleuthère Irénée du Pont, first produced gunpowder and later cellulose-based
paints. Following WWI, DuPont produced synthetic ammonia and other chemicals. DuPont began
experimenting with the development of cellulose based fibers, eventually producing the synthetic
fiber rayon. DuPont's experience with rayon was an important precursor to its development and
marketing of nylon.[15]:8,64,236
DuPont's invention of nylon spanned an eleven-year period, ranging from the initial research
program in polymers in 1927 to its announcement in 1938, shortly before the opening of the 1939
New York World's Fair.[6] The project grew from a new organizational structure at DuPont,
suggested by Charles Stine in 1927, in which the chemical department would be composed of
several small research teams that would focus on "pioneering research" in chemistry and would
"lead to practical applications".[15]:92 Harvard instructor Wallace Hume Carothers was hired to
direct the polymer research group. Initially he was allowed to focus on pure research, building on
and testing the theories of German chemist Hermann Staudinger.[16] He was very successful, as
research he undertook greatly improved the knowledge of polymers and contributed to
science.[17]
In the spring of 1930, Carothers and his team had already synthesized two new polymers. One was
neoprene, a synthetic rubber greatly used during World War II.[18] The other was a white elastic
but strong paste that would later become nylon. After these discoveries, Carothers' team was
made to shift its research from a more pure research approach investigating general
polymerization to a more practically-focused goal of finding "one chemical combination that
would lend itself to industrial applications".[15]:94
It wasn't until the beginning of 1935 that a polymer called "polymer 6-6" was finally produced.
Carothers' coworker, Washington University alumnus Julian W. Hill had used a cold drawing
method to produce a polyester in 1930.[19] This cold drawing method was later used by Carothers
in 1935 to fully develop nylon.[20] The first example of nylon (nylon 6,6) was produced on
February 28, 1935, at DuPont's research facility at the DuPont Experimental Station.[7] It had all
the desired properties of elasticity and strength. However, it also required a complex
manufacturing process that would become the basis of industrial production in the future. DuPont
obtained a patent for the polymer in September 1938,[21] and quickly achieved a monopoly of the
fiber.[17] Carothers died 16 months before the announcement of nylon, therefore he was never
able to see his success.[6]
The production of nylon required interdepartmental collaboration between three departments at
DuPont: the Department of Chemical Research, the Ammonia Department, and the Department of
Rayon. Some of the key ingredients of nylon had to be produced using high pressure chemistry,
the main area of expertise of the Ammonia Department. Nylon was considered a “godsend to the
Ammonia Department”,[15] which had been in financial difficulties. The reactants of nylon soon
constituted half of the Ammonia department's sales and helped them come out of the period of
the Great Depression by creating jobs and revenue at DuPont.[15]
DuPont's nylon project demonstrated the importance of chemical engineering in industry, helped
create jobs, and furthered the advancement of chemical engineering techniques. In fact, it
developed a chemical plant that provided 1800 jobs and used the latest technologies of the time,
which are still used as a model for chemical plants today.[15] The ability to acquire a large number
of chemists and engineers quickly was a huge contribution to the success of DuPont's nylon
project.[15]:100–101 The first nylon plant was located at Seaford, Delaware, beginning
commercial production on December 15, 1939. On October 26, 1995, the Seaford plant was
designated a National Historic Chemical Landmark by the American Chemical Society.[22]
Early marketing strategies
An important part of nylon's popularity stems from DuPont's marketing strategy. DuPont
promoted the fiber to increase demand before the product was available to the general market.
Nylon's commercial announcement occurred on October 27, 1938, at the final session of the
Herald Tribune's yearly "Forum on Current Problems", on the site of the approaching New York
City world's fair.[16][17]:141 The "first man-made organic textile fiber" which was derived from
"coal, water and air" and promised to be "as strong as steel, as fine as the spider's web" was
received enthusiastically by the audience, many of them middle-class women, and made the
headlines of most newspapers.[17]:141 Nylon was introduced as part of "The world of tomorrow"
at the 1939 New York World's Fair[23] and was featured at DuPont's "Wonder World of
Chemistry" at the Golden Gate International Exposition in San Francisco in 1939.[16][24] Actual
nylon stockings were not shipped to selected stores in the national market until May 15, 1940.
However, a limited number were released for sale in Delaware before that.[17]:145–146 The first
public sale of nylon stockings occurred on October 24, 1939, in Wilmington, Delaware. 4,000 pairs
of stockings were available, all of which were sold within three hours.[16]
Another added bonus to the campaign was that it meant reducing silk imports from Japan, an
argument that won over many wary customers. Nylon was even mentioned by President
Roosevelt's cabinet, which addressed its "vast and interesting economic possibilities" five days
after the material was formally announced.[17]
However, the early excitement over nylon also caused problems. It fueled unreasonable
expectations that nylon would be better than silk, a miracle fabric as strong as steel that would
last forever and never run.[17]:145–147[13] Realizing the danger of claims such as "New Hosiery
Held Strong as Steel" and "No More Runs", DuPont scaled back the terms of the original
announcement, especially those stating that nylon would possess the strength of steel.[17]
Also, DuPont executives marketing nylon as a revolutionary man-made material did not at first
realize that some consumers experienced a sense of unease and distrust, even fear, towards
synthetic fabrics.[17]:126–128 A particularly damaging news story, drawing on DuPont's 1938
patent for the new polymer, suggested that one method of producing nylon might be to use
cadaverine (pentamethylenediamine),[a] a chemical extracted from corpses. Although scientists
asserted that cadaverine was also extracted by heating coal, the public often refused to listen. A
woman confronted one of the lead scientists at DuPont and refused to accept that the rumour was
not true.[17]:146–147
DuPont changed its campaign strategy, emphasizing that nylon was made from "coal, air and
water", and started focusing on the personal and aesthetic aspects of nylon, rather than its
intrinsic qualities.[17]:146–147 Nylon was thus domesticated,[17]:151–152 and attention shifted
to the material and consumer aspect of the fiber with slogans like "If it's nylon, it's prettier, and
oh! How fast it dries!".[15]:2
Production of nylon fabric
Nylon stockings being inspected in Malmö, Sweden, in 1954
After nylon's nationwide release in 1940, production was increased. 1300 tons of the fabric were
produced during 1940.[15]:100 During their first year on the market, 64 million pairs of nylon
stockings were sold.[15]:101 In 1941, a second plant was opened in Martinsville, Virginia due to
the success of the fabric.[25]
Close-up photograph of the knitted nylon fabric used in stockings
Nylon fibers visualized using scanning electron microscopy
While nylon was marketed as the durable and indestructible material of the people, it was sold at
almost twice the price of silk stockings ($4.27 per pound of nylon versus $2.79 per pound of
silk).[15]:101 Sales of nylon stockings were strong in part due to changes in women's fashion. As
Lauren Olds explains: "by 1939 [hemlines] had inched back up to the knee, closing the decade just
as it started off". The shorter skirts were accompanied by a demand for stockings that offered
fuller coverage without the use of garters to hold them up.[26]
However, as of February 11, 1942, nylon production was redirected from being a consumer
material to one used by the military.[16] DuPont's production of nylon stockings and other lingerie
stopped, and most manufactured nylon was used to make parachutes and tents for World War
II.[27] Although nylon stockings already made before the war could be purchased, they were
generally sold on the black market for as high as $20.[25]
Once the war ended, the return of nylon was awaited with great anticipation. Although DuPont
projected yearly production of 360 million pairs of stockings, there were delays in converting back
to consumer rather than wartime production.[16] In 1946, the demand for nylon stockings could
not be satisfied, which led to the Nylon riots. In one case, an estimated 40,000 people lined up in
Pittsburgh to buy 13,000 pairs of nylons.[13] In the meantime, women cut up nylon tents and
parachutes left from the war in order to make blouses and wedding dresses.[28][29] Between the
end of the war and 1952, production of stockings and lingerie used 80% of the world's nylon.
DuPont put a lot of focus on catering to the civilian demand, and continually expanded its
production.
Introduction of nylon blends
As pure nylon hosiery was sold in a wider market, problems became apparent. Nylon stockings
were found to be fragile, in the sense that the thread often tended to unravel lengthwise, creating
'runs'.[15]:101 People also reported that pure nylon textiles could be uncomfortable due to
nylon's lack of absorbency.[30] Moisture stayed inside the fabric near the skin under hot or moist
conditions instead of being "wicked" away.[31] Nylon fabric could also be itchy, and tended to
cling and sometimes spark as a result of static electrical charge built up by friction.[32][33] Also,
under some conditions stockings could decompose[17] turning back into nylon's original
components of air, coal, and water. Scientists explained this as a result of air pollution, attributing
it to London smog in 1952, as well as poor air quality in New York and Los Angeles.[34][35][36]
The solution found to problems with pure nylon fabric was to blend nylon with other existing
fibers or polymers such as cotton, polyester, and spandex. This led to the development of a wide
array of blended fabrics. The new nylon blends retained the desirable properties of nylon
(elasticity, durability, ability to be dyed) and kept clothes prices low and affordable.[27]:2 As of
1950, the New York Quartermaster Procurement Agency (NYQMPA), which developed and tested
textiles for the army and navy, had committed to developing a wool-nylon blend. They were not
the only ones to introduce blends of both natural and synthetic fibers. America's Textile Reporter
referred to 1951 as the "Year of the blending of the fibers".[37] Fabric blends included mixes like
"Bunara" (wool-rabbit-nylon) and "Casmet" (wool-nylon-fur).[38] In Britain in November 1951, the
inaugural address of the 198th session of the Royal Society for the Encouragement of Arts,
Manufactures and Commerce focused on the blending of textiles.[39]
DuPont's Fabric Development Department cleverly targeted French fashion designers, supplying
them with fabric samples. In 1955, designers such as Coco Chanel, Jean Patou, and Christian Dior
showed gowns created with DuPont fibers, and fashion photographer Horst P. Horst was hired to
document their use of DuPont fabrics.[13] American Fabrics credited blends with providing
"creative possibilities and new ideas for fashions which had been hitherto undreamed of."[38]
Origin of the name
DuPont went through an extensive process to generate names for its new product.[17]:138–139 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. Since the
products were not really run-proof, the vowels were swapped to produce "nuron", which was
changed to "nilon" "to make it sound less like a nerve tonic". For clarity in pronunciation, the "i"
was changed to "y."[13][40]
Longer-term popularity
In spite of oil shortages in the 1970s, consumption of nylon textiles continued to grow by 7.5 per
cent per annum between the 1960s and 1980s.[41] Overall production of synthetic fibers,
however, dropped from 63% of the worlds textile production in 1965, to 45% of the world's textile
production in early 1970s.[41] The appeal of "new" technologies wore off, and nylon fabric "was
going out of style in the 1970s".[15] Also, consumers became concerned about environmental
costs throughout the production cycle: obtaining the raw materials (oil), energy use during
production, waste produced during creation of the fiber, and eventual waste disposal of materials
that were not biodegradable.[41] Synthetic fibers have not dominated the market since the 1950s
and 1960s. As of 2007, nylon continued to represent about 12% (8 million pounds) of the world's
production of synthetic fibers.[13] As one of the largest engineering polymer families, the global
demand of nylon resins and compounds was valued at roughly US$20.5 billion in 2013. The market
is expected to reach US$30 billion by 2020 by following an average annual growth of 5.5%.[42]
Although pure nylon has many flaws and is now rarely used, its derivatives have greatly influenced
and contributed to society. From scientific discoveries relating to the production of plastics and
polymerization, to economic impact during the depression and the changing of women's fashion,
nylon was a revolutionary product.[13] The Lunar Flag Assembly, the first flag planted on the
moon in a symbolic gesture of celebration, was made of nylon. The flag itself cost $5.50, but had
to have a specially-designed flagpole with a horizontal bar so that it would appear to "fly".[43][44]
One historian describes nylon as "an object of desire", comparing the invention to Coca-Cola in the
eyes of 20th century consumers.[15]
Chemistry
External video
"Making Nylon", Bob Burk, CHEM 1000, Carleton University, Ottawa, Canada
"Making Nylon 6,6"
"Nylon production", Royal Society of Chemistry
"Nylon and Rayon Manufacture 1949", Encyclopedia Britannica Films
Nylons are condensation polymers or copolymers, formed by reacting difunctional monomers
containing equal parts of amine and carboxylic acid, so that amides are formed at both ends of
each monomer in a process analogous to polypeptide biopolymers. Most nylons are made from
the reaction of a dicarboxylic acid with a diamine (e.g. PA66) or a lactam or amino acid with itself
(e.g. PA6).[45] In the first case, the "repeating unit" consists of one of each monomer, so that they
alternate in the chain, similar to the so-called ABAB structure of polyesters and polyurethanes.
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 second case (so called AA), the repeating
unit corresponds to the single monomer.[9]:45–50[46]
Nomenclature
In common usage, the prefix "PA" (polyamide) or the name "Nylon" are used interchangeably and
are equivalent in meaning.
The nomenclature used for nylon polymers was devised during the synthesis of the first simple
aliphatic nylons and uses numbers to describe the number of carbons in each monomer unit,
including the carbon(s) of the carboxylic acid(s).[47][48] Subsequent use of cyclic and aromatic
monomers required the use of letters or sets of letters. One number after "PA" or "Nylon"
indicates a homopolymer which is monadic or based on one amino acid (minus H2O) as monomer:
PA 6 or Nylon 6: [NH−(CH2)5−CO]n made from ε-Caprolactam.
Two numbers or sets of letters indicate a dyadic homopolymer formed from two monomers: one
diamine and one dicarboxylic acid. The first number indicates the number of carbons in the
diamine. The two numbers should be separated by a comma for clarity, but the comma is often
omitted.
PA or Nylon 6,10 (or 610) : [NH−(CH2)6−NH−CO−(CH2)8−CO]n made from hexamethylenediamine
and sebacic acid;
For copolymers the comonomers or pairs of comonomers are separated by slashes:
PA 6/66 : [NH-(CH2)6−NH−CO−(CH2)4−CO]n−[NH−(CH2)5−CO]m made from caprolactam,
hexamethylenediamine and adipic acid ;
PA 66/610 : [NH−(CH2)6−NH−CO−(CH2)4−CO]n−[NH−(CH2)6−NH−CO−(CH2)8−CO]m made from
hexamethylenediamine, adipic acid and sebacic acid.
The term polyphthalamide (abbreviated to PPA) is used when 60% or more moles of the carboxylic
acid portion of the repeating unit in the polymer chain is composed of a combination of
terephthalic acid (TPA) and isophthalic acid (IPA).
Types of nylon
Nylon 66
Main article: Nylon 66
Wallace Carothers at DuPont patented nylon 66 using amides.[21][49][50] In the case of nylons
that involve reaction of a diamine and a dicarboxylic acid, 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. The salt is crystallized to purify it and obtain the desired precise stoichiometry. Heated to
285 °C (545 °F), the salt reacts to form nylon polymer with the production of water.
Nylon 6
Main article: Nylon 6
The synthetic route using lactams (cyclic amides) was developed by Paul Schlack at IG Farben,
leading to nylon 6, or polycaprolactam — formed by a ring-opening polymerization. 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.
The 428 °F (220 °C) melting point of nylon 6 is lower than the 509 °F (265 °C) melting point of
nylon 66.[51]
Nylon 510
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Nylon 510, made from pentamethylene diamine and sebacic acid, was studied by Carothers even
before nylon 66 and has superior properties, but is more expensive to make. In keeping with this
naming convention, "nylon 6,12" or "PA 612" is a copolymer of a 6C diamine and a 12C diacid.
Similarly for PA 510 PA 611; PA 1012, etc. Other nylons include copolymerized dicarboxylic
acid/diamine products that are not based upon the monomers listed above. For example, some
fully aromatic nylons (known as "aramids") 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 PA 66/6; copolymers of PA 66/6/12; and others. In
general linear polymers are the most useful, but it is possible to introduce branches in nylon by
the condensation of dicarboxylic acids with polyamines having three or more amino groups.
The general reaction is:
Condensation polymerization diacid diamine.svg
Two molecules of water are 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.
Industrial synthesis is usually done by heating the acids, amines or lactams to remove water, but in
the laboratory, diacid chlorides can be reacted with diamines. For example, a popular
demonstration of interfacial polymerization (the "nylon rope trick") is the synthesis of nylon 66
from adipoyl chloride and hexamethylene diamine.
Nylon 1,6
Main article: Nylon 1,6
Nylons can also be synthesized from dinitriles using acid catalysis. For example, this method is
applicable for preparation of nylon 1,6 from adiponitrile, formaldehyde and water.[52]
Additionally, nylons can be synthesized from diols and dinitriles using this method as well.[53]
Monomers
Nylon monomers are manufactured by a variety of routes, starting in most cases from crude oil
but sometimes from biomass. Those in current production are described below.
Amino acids and lactams
ε-Caprolactam: Crude oil → benzene → cyclohexane → cyclohexanone → cyclohexanone oxime →
caprolactam
11-aminoundecanoic acid: Castor oil → ricinoleic acid → methylricinoleate → methyl-11-
undecenoate → undecenoic acid → 11-undecenoic acid → 11-bromoundecanoic acid → 11-
aminoundecanoic acid[54]
Laurolactam: Butadiene → cyclododecatriene → cyclododecane → cyclododecanone →
cyclododecanone oxime → laurolactam
Diacids
Adipic acid: Crude oil → benzene → cyclohexane → cyclohexanone + cyclohexanol → adipic acid
Sebacic acid (decanedioic acid): Castor oil → ricinoleic acid → sebacic acid
Dodecanedioic acid: Butadiene → Cyloclododecatriene → cyclododecane → (oxidation) →
Dodecanedioic acid
Terephthalic acid: Crude oil → p-xylene → terephthalic acid
Isophthalic acid: Crude oil → m-xylene → isophthalic acid
Diamines
Various diamine components can be used, which are derived from a variety of sources. Most are
petrochemicals, but bio-based materials are also being developed.
Tetramethylene diamine (putrescine): Crude oil → propylene → acrylonitrile → succinonitrile →
tetramethylene diamine
Hexamethylene diamine (HMD): Crude oil → butadiene → adiponitrile → hexamethylene diamine
1,9-diaminononane: Crude oil → butadiene → 7-octen-1-al → 1,9-nonanedial → 1,9-
diaminononane[55]
2-methyl pentamethylene diamine: a by product of HMD production
Trimethyl Hexamethylene diamine (TMD): Crude oil → propylene → acetone → isophorone →
TMD
m-xylylene diamine (MXD): Crude oil → m-xylene → isophthalic acid → isophthalonitrile → m-
xylylene diamine[56]
1,5-pentanediamine (cadaverine) (PMD): starch (e.g. cassava) → glucose → lysine → PMD.[57]
Polymers
Due to the large number of diamines, diacids and aminoacids that can be synthesized, many nylon
polymers have been made experimentally and characterized to varying degrees. A smaller number
have been scaled up and offered commercially, and these are detailed below.
Homopolymers
Homopolymer nylons derived from one monomer
Monomer Polymer
caprolactam 6
11-aminoundecanoic acid 11
ω-aminolauric acid 12
Examples of these polymers that are or were commercially available
PA6 Lanxess Durethan B[58]
PA11 Arkema Rilsan[59]
PA12 Evonik Vestamid L[60]
Homopolymer polyamides derived from pairs of diamines and diacids (or diacid derivatives).
Shown in the table below are polymers which are or have been offered commercially either as
homopolymers or as a part of a copolymer.
Commercial homopolymer polyamides
1,4-diamino-butane 1,5-diamino-pentane MPMD HMD MXD Nonane-diamine
Decane-diamine Dodecane-diamine bis-(para-amino-cyclohexyl)-methane
trimethyl-hexamethylene-diamine
Adipic acid 46 D6 66 MXD6
Sebacic acid 410 510 610 1010
Dodecanedioic acid 612 1212 PACM12
Terephthalic acid 4T DT 6T 9T 10T 12T
TMDT
Isophthalic acid DI 6I
Examples of these polymers that are or were commercially available
PA46 DSM Stanyl[61]
PA410 DSM Ecopaxx[62]
PA4T DSM Four Tii[63]
PA66 DuPont Zytel[64]
Copolymers
It is easy to make mixtures of the monomers or sets of monomers used to make nylons to obtain
copolymers. This lowers crystallinity and can therefore lower the melting point.
Some copolymers that have been or are commercially available are listed below:
PA6/66 DuPont Zytel[65]
PA6/6T BASF Ultramid T (6/6T copolymer)[66]
PA6I/6T DuPont Selar PA[67]
PA66/6T DuPont Zytel HTN[66]
PA12/MACMI EMS Grilamid TR[68]
Blends
Most nylon polymers are miscible with each other allowing a range of blends to be made. The two
polymers can react with one another by transamidation to form random copolymers.[69]
According to their crystallinity, polyamides can be:
semi-crystalline:
high crystallinity: PA46 and PA66;
low crystallinity: PAMXD6 made from m-xylylenediamine and adipic acid;
amorphous: PA6I made from hexamethylenediamine and isophthalic acid.
According to this classification, PA66, for example, is an aliphatic semi-crystalline homopolyamide.
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, 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.[70] The reaction is of the type:
Amide hydrolysis.svg
Environmental impact, incineration and recycling
Berners-Lee calculates the average greenhouse gas footprint of nylon in manufacturing carpets at
5.43 kg CO2 equivalent per kg, when produced in Europe. This gives it almost the same carbon
footprint as wool, but with greater durability and therefore a lower overall carbon footprint.[71]
Data published by PlasticsEurope indicates for nylon 66 a greenhouse gas footprint of 6.4 kg CO2
equivalent per kg, and an energy consumption of 138 kJ/kg.[72] When considering the
environmental impact of nylon, it is important to consider the use phase. In particular when cars
are lightweight, significant savings in fuel consumption and CO2 emissions are achieved.
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 slowly.[b] Discarded nylon
fabric takes 30–40 years to decompose.[73] Nylon is a robust polymer and lends itself well to
recycling. Much nylon resin is recycled directly in a closed loop at the injection molding machine,
by grinding sprues and runners and mixing them with the virgin granules being consumed by the
molding machine.[74]
Nylon can be recycled but only a few companies do so. Aquafil has demonstrated recycling fishing
nets lost in the ocean into apparel[75] Vanden recycles Nylon and other polyamides (PA) and has
operations in UK, Australia, Hong Kong, UAE, Turkey and Finland.[76]
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.[77] 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.
Hydrogen bonding in Nylon 6,6 (in mauve).
Nylon 66 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 (see the figure opposite). Nylon 510 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 industry 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. In
practice, nylon fibers are most often drawn using heated rolls at high speeds.[78]
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.
Nylons are hygroscopic, and will absorb or desorb moisture as a function of the ambient humidity.
Variations in moisture content have several effects on the polymer. Firstly, the dimensions will
change, but more importantly moisture acts as a plasticizer, lowering the glass transition
temperature (Tg), and consequently the elastic modulus at temperatures below the Tg[79]
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.
Characteristics
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"
High 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.
Variation of luster: nylon has the ability to be very lustrous, semi-lustrous 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 to infrared light (−12 dB)[80][clarification needed]
Flammability
Nylon clothing tends to be less flammable than cotton and rayon, but nylon fibers may melt and
stick to skin.[81][82]
Uses of nylon
Nylon was first used commercially in a nylon-bristled toothbrush in 1938,[11][12] followed more
famously in women's stockings or "nylons" which were shown at the 1939 New York World's Fair
and first sold commercially in 1940.[13] Its use increased dramatically during World War II, when
the need for fabrics increased dramatically.
Nylon fibers
These worn out nylon stockings will be reprocessed and made into parachutes for army fliers c.
1942
Blue Nylon fabric ball gown by Emma Domb, Science History Institute
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
nearly all of the rest. By August 1945, manufactured fibers had taken a market share of 25%, at the
expense of cotton. After the war, because of shortages of both silk and nylon, nylon parachute
material was sometimes repurposed to make dresses.[83]
Nylon 6 and 66 fibers are used in carpet manufacture.
Nylon is one kind of fibers used in tire cord. Herman E. Schroeder pioneered application of nylon in
tires.
Molds and resins
Nylon resins are widely used in the automobile industry especially in the engine
compartment.[84][2]:514
Molded nylon is used in hair combs and mechanical parts such as machine screws, gears, gaskets,
and other low- to medium-stress components previously cast in metal.[85][86] Engineering-grade
nylon is processed by extrusion, casting, and 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
molded nylon.[87][88] For use in tools such as spudgers, nylon is available in glass-filled variants
which increase structural and impact strength and rigidity, and molybdenum disulfide-filled
variants which increase lubricity. Nylon can be used as the matrix material in composite materials,
with reinforcing fibers like glass or carbon fiber; such a composite has a higher density than pure
nylon.[89] Such thermoplastic composites (25% to 30% glass fiber) 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.[90]
Nylon was used to make the stock of the Remington Nylon 66 rifle.[91] The frame of the modern
Glock pistol is made of a nylon composite.[92]
Food packaging
Nylon resins are used as a component of food packaging films where an oxygen barrier is
needed.[4] Some of the terpolymers based upon nylon are used every day in packaging. Nylon has
been used for meat wrappings and sausage sheaths.[93] The high temperature resistance of nylon
makes it useful for oven bags.[94]
Filaments
Nylon filaments are primarily used in brushes especially toothbrushes[11] and string trimmers.
They are also used as monofilaments in fishing line. Nylon 610 and 612 are the most used
polymers for filaments.
Its various properties also make it very useful as a material in additive manufacturing; specifically
as a filament in consumer and professional grade fused deposition modeling 3D printers.
Other forms
Extruded profiles
Nylon resins can be extruded into rods, tubes and sheets.[2]:209
Powder coating
Nylon powders are used to powder coat metals. Nylon 11 and nylon 12 are the most widely
used.[2]:53
Instrument strings
In the mid-1940s, classical guitarist Andrés Segovia mentioned the shortage of good guitar strings
in the United States, particularly his favorite Pirastro catgut strings, to a number of foreign
diplomats at a party, including General Lindeman of the British Embassy. A month later, the
General presented Segovia with some nylon strings which he had obtained via some members of
the DuPont family. Segovia found that although the strings produced a clear sound, they had a
faint metallic timbre which he hoped could be eliminated.[95]
Nylon strings were first tried on stage by Olga Coelho in New York in January, 1944.[96]
In 1946, Segovia and string maker Albert Augustine were introduced by their mutual friend
Vladimir Bobri, editor of Guitar Review. On the basis of Segovia's interest and Augustine's past
experiments, they decided to pursue the development of nylon strings. DuPont, skeptical of the
idea, agreed to supply the nylon if Augustine would endeavor to develop and produce the actual
strings. After three years of development, Augustine demonstrated a nylon first string whose
quality impressed guitarists, including Segovia, in addition to DuPont.[95]
Wound strings, however, were more problematic. Eventually, however, after experimenting with
various types of metal and smoothing and polishing techniques, Augustine was also able to
produce high quality nylon wound strings.[95]
