1.
Introduction.
Ever since it first came on the market, nylon's many
uses have greatly influenced most facets of our daily
lives, including mountaineering. The story of how it
came into being, however, must be preceded by a few
words about its place in the chemical world.
Nylon is a polymer obtained by the condensation of diamines
with bicarboxylic organic acids, or from omega-amino
acids. In more specific terms, it is a polyamide, i.e.
one of a class of polymers whose molecular chains are
formed by regularly spaced -CONH- amide groups. Like
all polyamides, nylon is produced by step polymerisation
in (the molecular mass increases as a function of reaction
time). The characteristic features of each nylon are
its structural unit or units (a unit being the residue
of the monomers bonded during polymerisation to form
the macromolecule), and the average number of units
per molecule namely the degree of polymerisation. Since
Carothers and his group invented nylon, a nylon or a
polyamide has been conventionally accompanied by some
figures indicating the number of carbon atoms in the
structural unit(s). The first figure shows the carbon
atoms of the diamine, the second those of the bicarboxylic
acid. The nylon invented by Carothers and known as nylon
66 or polyamide 66, or poly(hexamethylneadipamide),
therefore, is read as six-six, not sixtysix, which means
that it is composed of two structural units, each with
six carbon atoms, namely the residues of hexamethylendiamine
(H2N(CH2)6NH2) and adipic acid (HOOC(CH2)4COOH). Nylon
6 or poly(6-caprolactam), another important polymer,
is composed of a single structural unit, namely the
apparent residue of 6-aminocaproic acid (H2N(CH2)4COOH).
The story of the birth of nylon is inevitably intermingled
with the duPont de Nemours family and the E. I. DuPont
de Nemours Company and its inventor, Wallace Hume Carothers.
2. The duPont de Nemours family
and the E. I. DuPont Company.
In the period known as the Terror during the French
Revolution, when noble heads were ready fodder for
the guillotine, Viscount duPont de Nemours, a banker,
fled to the United States with his capital. His family
turned their hands to the manufacture of explosives,
particularly black powder. In 1903 Pierre Samuel duPont
de Nemours took over the business and when smokeless
powder was invented, he promptly stopped producing
black powder and dynamite and switched to nitrocellulose
explosives. The first world war was obviously a goldmine
for both the
When the war came to an end in 1918, Pierre Samuel
gained control of William Crapo Durant's General Motors
and became its president. Under his guidance, GM made
giant strides and was soon turning out more cars than
its rival Ford.
Irénée, Pierre's brother, took over
the presidency of DuPont in 1919. His admirable far-sightedness
told him it was time for the company to add another
string to its bow by entering the field of what we
now call fine chemistry, namely the production of
chemicals with a high added value. Explosives of all
kinds were to be joined by dyes, drugs and textile
fibres.
In 1916, DuPont had acquired Levinstein's dye technologies
in England. Even so, it was unable to compete with
Germany's big firms when they were once again permitted
to export their products to the United State after
the war. A short, sharp remedy was sought and found.
Lured by very high salaries, five of Bayer's top-level
technicians crossed the Atlantic together with their
wives, children and servants.
In 1920, DuPont moved into textiles in a joint venture
with the French manufacturer Comptoir des Textiles
Artificiels and set up a rayon factory at Buffalo
in the State of New York. Here, too, the profits were
enormous because rayon was so much cheaper than natural
silk. Nitration of cellulose was not abandoned, however.
Explosives were still produced, along with paints,
cellophane and photographic films.
It was also in 1920 that DuPont's researchers discovered,
quite by chance, that a small quantity of sodium acetate
transformed a nitrocellulose gel with a high solid
content into a smooth flowing syrupy liquid. This
was the beginning of the nitro paints, usually called
Duco (an abbreviation of DuPont Company), employed
for car bodies until some twenty years ago when they
were superseded by the acrylics.
In 1922, Pierre Samuel told his brother Irénée
that Thomas Midgley, one of GM's researchers, had
invented tetraethyl lead, the antiknock agent added
to petrol for better combustion and used in premium
grade fuel until a few months ago. DuPont's researchers
were given the task of working up the process and
a production plant.
From what has been said so far, one can readily imagine
it was not all that difficult for Dr. Stine, head
of DuPont's chemical Department since 1924, to convince
the company's President and the Executive Committee
in 1927 to put twenty thousand dollars into a project
for research in pure science.
At Wilmington, Delaware, this new venture took shape
as the company's Pure Science Section (jokingly referred
to as Purity Hall). It was easy enough to find the
heads for colloid chemistry researches (Prof. E.O.
Kraemer, University of Wisconsin) and for the catalysis
group (Dr. G. Taylor, DuPont). As the head of organic
research, many voices were raised in favour of Dr.
Wallace Hume Carothers, instructor in organic chemistry
at Harvard since 1926. And so it was that the path
of Carothers, the inventor of nylon, crossed that
of DuPont when, on 1 February 1928 and after much
anxious heart searching, he finally entered the company's
employ.
3. Wallace Hume Carothers.
But who was this Carothers ? Born at Burlington, Iowa,
on 27 April 1896, he was a prey to periods of deep
depression that in the end led to alcoholism and suicide
in a room at the Philadelphia Hotel in Philadelphia
on 29 April 1937.
In July 1915, Carothers qualified as an accountant
at the Des Moines Capital City Commercial College
in Iowa and in the following September entered Tarkio
College at Tarkio, Missouri, to follow its courses
in science (chemistry, physics, mathematics, etc.).
Initially an assistant in the Commercial Department
and then in English for the first two years, he moved
to the Chemistry Department and in 1920 took his B.Sc.
In September of the same year, he joined the Chemistry
Department of the University of Illinois and took
his M.A. the following summer. During the academic
year 1921-22, he lectured on analytical chemistry
and physical chemistry at the University of South
Dakota. In 1922, he returned to the University of
Illinois and started work on his doctoral thesis on
the catalytic reduction of aldehydes with osmium oxide
under the supervision of Prof. Roger Adams. He took
his Ph.D. in 1924 and joined the university's staff
as an instructor in organic chemistry. Two years later,
he was offered a similar post at Harvard and quickly
stood out as a brilliant organic chemist.
4. Carothers and his research group.
Carothers and his researchers at DuPont had their
first success in 1930 when they synthesized polychloroprene.
It made its debut on the market as Duprene, and in
1936 it became the familiar neoprene, the world's
first synthetic rubber and still unrivalled for many
applications, such as O-rings and wetsuits.
Carothers’s research team had discovered the
tricks needed to produce macromolecules (superpolyesters)
with molecular weights of more than 4000, which had
once seemed an insuperable limit. They were removal
of the small molecule (usually water) formed as a
by-product of the polyesterification reaction; need
to have a ratio as close as possible to 1 between
the reacting carboxyl and hydroxyl groups throughout
the polyesterification; the intervention of reactions,
which Carothers and his colleagues called transesterification,
and. These, however, were laboratory achievements
whose practical applications were confined to fibres
on which was observed for the first time the orientation
produced by what the researchers called cold drawing.
By the end of 1931, DuPont had not very much to show
as the outcome of its basic research programme. As
we have said, its superpolyester fibres were seen
as oddities with no hope of a commercial future, while
Duprene's full range of uses was still unknown and
its chances of competing with natural rubber were
hamstrung by the latter's nose-diving prices during
the Great Depression in 1929. To make matters worse,
Carothers was wont to keep the scientific community
informed of all the results of his research in papers
published or read at congresses. As events were to
show, some things should have been kept under wraps
or in the bottom drawer, since their over-hasty revelation
enabled others to steal a march on Carothers and his
group. Two examples can be cited.
The first concerns nylon 6 or poly(6-caprolactam).
In 1930, Gérard Berchet together with Carothers
investigated the polymerisation of 6-aminocaproic
acid and obtained a low molecular weight polymer togheter
with a cyclic compound they called lactam.
They considered that their line of research had come
to an end and announced that lactam did not polymerise
under polyamide-forming conditions in either the presence
or the absence of a catalyst. When I.G.Farben Industrie's
technicians in Germany knew about Carothers' nylon
66, they dug out his paper on 6-caprolactam and very
soon (in 1941) managed to synthesise nylon 6, which
was sold as Perlon.
If Carothers and Berchet had kept their results to
themselves instead of rushing into print, they and
DuPont would certainly have managed to produce nylon
6.
The second story runs as follows. One of the earliest
polyesters studied by Carothers in conjunction with
J. Arvin (1929) was that obtained when phthalic acid
is condensed with ethylene glycol. The results were
not entirely disappointing, but by no means encouraging.
What was produced, in fact, was simply a low molecular
weight (about 4000) vitreous resin and the research
was abandoned.
Even today, one fails to understand why Carothers
and Arvin did not try replacing phthalic acid, whose
two carboxyls are in the ortho position, with terephthalic
acid, who two carboxyls are in the para position.
Had they done so, they would have been the earlier
discoverers of poly(ethylene terephthalate), otherwise
known as Terylene, the strong polyester fibre perhaps
even more widely used than nylon.
Despite the crisis of the early 1930s, rayon continued
to sell well. One disadvantage of this artificial
silk, however, was that, like its natural silk, its
filaments reflect the light, whereas wool, cotton
and linen fabrics have a duller look and never dazzle.
There was no particular reason for preferring an opaque
to a shiny material. The dictates of fashion, however,
determined the preferences of the late 1920s and rayon
fibres were duly made opaque by the addition of very
fine titanium oxide. DuPont was the not the first
to develop this technique and had to manufacture through
licensing agreements with its competitors.
The fact that rayon, whether shiny or dull, had made
such gigantic strides over the course of the years
led Dr. E. J. Bolton, head of the Company's Chemical
Department, to stress the importance of devising an
entirely new textile fibre in his end-year report
for 1933.
At the beginning of 1934, therefore, Carothers in
response to the suggestions of Dr. Bolton took a second
look at the polyamides that had given so little satisfaction
a few years earlier. A polyamide can be synthesised
in the same way as a polyester by intermolecular condensation
with either an organic bicarboxylic acid and a diamine
or by intramolecular condensation of an omega-aminoacid.
A water molecule is always eliminated in each condensation
step. The degree of polymerisation depends on how
the experimenter manages to shift the reaction equilibrium
towards the formation of the polymer, which can only
be done by removing the water formed by condensation
of the functional groups involved in the reaction.
The first problem to be solved was how to get over
the experimental difficulties this involves.
In their previous work on the derivation of polyamides
from 6-caprolactam, Carothers and Hill were unable
to obtain fibres from the small amount of polymer
they obtained because its melting point was so high
that it decomposed before the melting temperature
could be reached. Carothers' first objective, therefore,
was to produce polymers whose melting point was high
enough (obviously higher than that of his polyesters)
to enable them to be used as fibres, but low enough
to allow them to be processed without decomposing.
This in turn posed a second problem. The way to lower
the melting point of a polyamide would be to use an
amino acid with a large number of methylene groups,
since Carothers and Hill had already shown that a
very long chain paraffin melts at about 100°C.
There was also the possibility that intramolecular
condensations might lead to the formation of cyclic
compounds competing with the intermolecular condensations
forming the polymer chain. Carothers' work on such
compounds had shown that rings with more than 10 atoms
are rarely formed. This, too, pointed to the employment
of an omega-amino acid whose amine and carboxyl groups
were separated by an appropriate number of methylene
groups.
Carothers therefore asked one of his coworkers, Dr.
Donald Coffman, to prepare 9-aminononanoic acid (H2N(CH2)8COOH),
in which eight methylene groups separate the amine
and carboxyl functional groups involved in the condensation
reaction. He expected that this would give a polyamide
whose melting point was low enough to provide fibres
without decomposing. In addition, there was very little
likelihood that 10-atom cyclic compounds would be
formed.
A way for removing as much water as possible, in order
to obtain a polymer with polymerisation degree high
enough for the formation of fibres, remained to be
found. Carothers decided to replace 9-aminononanoic
acid with its ethyl ester since this would result
in formation of much more easily removable ethyl alcohol
during polycondensation. On 23 March 1934, Carothers
asked Coffman to prepare this ester. Between 4 April
and 21 May 1934, Coffman was able to obtain some sufficiently
pure ester. When he polymerised it two days later,
he obtained polyammide 9, a polymer that at first
sight had all the features of a high molecular weight
product and was therefore a superpolyamide. On 24
May, Coffman heated it in a bath at 200°C, a little
higher than its melting point, dipped in a cold glass
rod and drew out a strong, not brittle filament that
produced shiny fibres when cold drawn.
These fibres were similar to and in some respects
better than natural silk and could thus have entirely
replaced it. Carothers, however, immediately realised
that they would make no headway on the market because
the monomer endowed with the degree purity needed
to obtain high molecular weights was hard to prepare
and handle. He therefore turned his attention to other
monomers and combinations of diamines and bicarboxylic
acids. By the end of July, Dr. W.R. Peterson had prepared
polyamide 5-10, another superpolyamide, by reacting
pentamethylenediamine H2N(CH2)5NH2 (5 carbon atoms)
with the ethyl diester of sebacic acid C2H5C0(CH2)8COOC2H5
(10 carbon atoms), with the elimination of ethyl alcohol.
Bolton, however, did not really believe that polyamide
5-10 could be turned into a marketable product and
continued to urge Carothers to carry out a systematic
investigation of potential polyamides. At the beginning
of 1935, this task was entrusted to Gérard
Berchet, whose preparation, purification and polymerisation
of diamines and bicarboxylic acids soon produced a
number of potentially interesting polyamides. One
of these, poly(hexamethyleneadipamide) or polyamide
66, was obtained from hexamethylenediamine and adipic
acid on 28 February - 1 March 1935.
This was a solid, horny mass that melted at 252-254°C
and an easy source of fibres, though such a high melting
point indicated that it would probably decompose during
hot drawing. Luckily for DuPont, however, this fear
proved groundless and what we now know as nylon was
born.
In the summer of 1935, Dr. Bolton virtually ordered
Carothers to concentrate on polyamide 66 as a likely
candidate for production on an industrial scale and
abandon polyamide 5-10. Its very attractive qualities,
in fact, were offset by the fact that sebacic acid
had to be made from castor oil, a raw material whose
production would never be able to keep up with the
demand for the new fibre, whereas adipic acid could
be and indeed was prepared from benzene, a petroleum
derivative and hence available ad lib.
Industrialisation of polyamide 66 proceeded at full
speed, but naturally required the involvement of dozens
of chemists and engineers. By this time, however,
it was becoming increasingly clear that Carothers
was no longer mentally fit to supervise and take part
in their work. Bolton thus required him to share his
responsibility for the research with Dr. Graves. Carothers
has always been given all the credit for the invention
of the new synthetic polyamidic fibre. Whereas in
other patent applications Carothers’s name was
accompanied by the one of the cowrker who had materialised
the invention in practical terms, those relating to
nylon, its preparation and uses (all lodged after
his death) bear his name only. In truth, of course,
he never took any substantial part in the development
of nylon.
5. Announcing of nylon.
By comparison with the broadcasting of the past, on
this occasion silence was the order of the day. Not
a word leaked out to the rest of the scientific world
from the day when Berchet completed the synthesis
of polyamide 66 on 1 March 1935 and its industrialisation
got under way until 20 September 1938, when three
patents were granted in the name of W.H.Carothers
to E.I. Dupont de Nemours and Company, Willmington,
Delware, as U.S. Patent 2,130,523 Linear polyamides
suitable for spinning into strong pliable fibers,
U.S. Patent 2,130,947 Diamine dicarboxylic acid salt
(suitable for forming spun fibers, etc.), which describes
the purification of hexamethyldiamine adipate crystals,
subsequently known as nylon salt, and U.S. Patent
2,130,948 Synthetic fibers, which describes the polymerisation
of hexamethylenediamine adipate acid to form poly(hexamethyleneadipamide).
On 22 September 1938, the New York Times carried an
article entitled New Silk Made on Chemical Base Rivals
Quality of Natural Product, and an editorial penned
four days later reported: a new kind of nylon has
been produced ... Because of its impact on the silk
trade.... Japan has reason to worry.
Man's very first synthetic fibre, stronger than steel,
fine as a spider's web, more elastic than any of the
common natural fibres, splendidly shiny and due to
be marketed with the commercial name of nylon, was
presented by Dr. Stine, a DuPont vice president, at
the New York World Fair on 27 October 1938. His words,
according to the papers, were received with little
more than polite respect until he mentioned that a
factory had begun to knit nylon hosiery and these
new stockings felt better than silk stockings, didn’t
bag or snag, and when they snagged they didn’t
run. At this point that passive audience come to see
Katherine Hepburn, the famous actress, stood and applauded.
Nylon immediately got off to a flying start. DuPont,
indeed, had to build another two plants to flank the
first, itself not yet fully worked up. The very first
product turned out, even before stockings, was bristles
for toothbrushes.
Heavy capital expenditures were needed to industrialise
nylon development as well as the production plants.
Nylon stockings quickly become known as nylons. They
were presented to the public for the first time at
the San Francisco International Exhibition in February
1939 and almost simultaneously made available to the
company's Wilmington employees only. In October, the
citizens of Wilmington itself were able to buy them.
On 15 May 1940 came the great moment when nylons were
placed on sale throughout the United States at USD
1.15 - 1.35 a pair. The shops were taken by storm
and almost five million pairs were bought on that
day alone.
When the United States came into the war a campaign
was mounted to collect nylon and nylons for the war
effort. Nylon was quickly employed for parachutes
fabric, brained parachute cord, outwear and tenting
and tire yarn and glider towrope, etc. The vanguard
of the U.S. Army floated to earth in Normandy carried
by and covered with nylon. During the war some 13,000
tonnes of nylon were produced per year. In 1945, nylons
came back to the shops, though about a couple of years
were needed to catch up with the stocking demand.
By 1949, production had raised to 25,000 tonnes a
year.
6. About the name.
The origin of the word nylon has been told in what may
be called an official story. But as in all stories,
there is a legend. One apocryphal versions were passed
on more by word of mouth than anything else and are
still better known and more widely believed than the
official story.
Throughout its development and prior to its introduction
on the market, polyamide 66 was simply referred to as
fibre 66. When the time came to launch it, a trade name
obviously had to be found. One year before nylon announcement,
Dr. H. Church, head of research at DuPont's rayon Department
at Buffalo, suggested playfully the acroym Duparooh,
which stood for DuPont "DuPont ulls a Rabbit Out
of hat". Names such as novasilk and synthesilk
were discarded because the company wanted its new synthetic
fibre to conquer the market on account of all its high
qualities and not just as a substitute for silk. A committee
of three formed in 1938 collected a list of 400 names
but no one of them met approval. Dr. E.K.Gladding, one
of the committee member, proposed Norun with stockings
in mind, but changed it to Nuron since also stockings
of the new fibre would run. Here, however, the question
of how this should be pronounced arose. An American
"noo" (= new) as in "noon" was possible,
but a British "new" would have seemed like
"neuron". Replacement of the "r"
by an "l" to form "nulon" was proposed,
but once again the sound of the "u" would
be uncertain and an expression such as "new nulon"
would also be cacophonic. At this point a vowel change
was suggested: "nilon" instead of "nulon".
But was this "ni" to be pronounced as in "need"
or in "nine" ? In the end, the name selection
committee opted for a "y". The pronunciation
problem was solved and "nylon" was born.
This is the official DuPont version. The legend is much
more intriguing and presumably offers one of the many
examples of a tendency among English-speaking peoples
to invent humorous, sarcastic or derogatory versions
of familiar acronyms. It was not very difficult, therefore,
for some wag to come up with "Now You Lose Old
Nippon" or "Now You Lousy Old Nippon".
Apart from the evident threat posed by nylon to Japan
as the largest producer of natural silk and hence the
end of its leadership in the manufacture of fibres and
choice fabrics, the period when nylon appeared was marked
by very strong anti-Japanese feelings. An American success
was thus accompanied by an open desire to offend Japan.
The two appealing versions probably saw the light at
the same time as nylon itself in October 1938 and quickly
spread from coast to coast. Such was their effect, indeed,
and so much better were they known than the official
version, that in February 1941 DuPont commissioned a
Japanese newspaper to publish a denial that the word
nylon had the meanings attributed to it. This however
has never become sufficiently known to dethrone the
legendary versions in the eyes of the mass of mankind,
even today.
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