The invention: A resilient, high-strength polymer with applications
ranging from women’s hose to safety nets used in space flights.
The people behind the invention:Wallace Hume Carothers (1896-1937),
an American organic chemist Charles M. A. Stine (1882-1954), an American chemist
and director of chemical research at Du Pont Elmer Keiser Bolton (1886-1968),
an American industrial chemist Pure Research In the twentieth century,
American corporations created industrial research laboratories.
Their directors became the organizers of inventions,
and their scientists served as the sources of creativity.
The research program of
E. I. Du Pont de Nemours and Company
(Du Pont), through its most famous invention—nylon—became the
model for scientifically based industrial research in the chemical
During World War I (1914-1918), Du Pont tried to diversify,
concerned that after the war it would not be able to expand with
only explosives as a product. Charles M. A. Stine, Du Pont’s director
of chemical research, proposed that Du Pont should move
into fundamental research by hiring first-rate academic scientists
and giving them freedom to work on important problems in
organic chemistry. He convinced company executives that a program
to explore the fundamental science underlying Du Pont’s
technology would ultimately result in discoveries of value to the
company. In 1927, Du Pont gave him a new laboratory for research.
Stine visited universities in search of brilliant, but not-yetestablished,
young scientists. He hired Wallace Hume Carothers.
Stine suggested that Carothers do fundamental research in polymer
chemistry.Before the 1920’s, polymers were a mystery to chemists. Polymeric
materials were the result of ingenious laboratory practice,
and this practice ran far ahead of theory and understanding. German
chemists debated whether polymers were aggregates of smaller
units held together by some unknown special force or genuine molecules
held together by ordinary chemical bonds.
German chemist Hermann Staudinger asserted that they were
large molecules with endlessly repeating units. Carothers shared
this view, and he devised a scheme to prove it by synthesizing very
large molecules by simple reactions in such a way as to leave no
doubt about their structure. Carothers’s synthesis of polymers revealed
that they were ordinary molecules but giant in size.
The Longest Molecule
In April, 1930, Carothers’s research group produced two major
innovations: neoprene synthetic rubber and the first laboratorysynthesized
fiber. Neither result was the goal of their research. Neoprene
was an incidental discovery during a project to study short
polymers of acetylene. During experimentation, an unexpected substance
appeared that polymerized spontaneously. Carothers studied
its chemistry and developed the process into the first successful synthetic
rubber made in the United States.
The other discovery was an unexpected outcome of the group’s
project to synthesize polyesters by the reaction of acids and alcohols.
Their goal was to create a polyester that could react indefinitely
to form a substance with high molecular weight. The scientists
encountered a molecular weight limit of about 5,000 units to the
size of the polyesters, until Carothers realized that the reaction also
produced water, which was decomposing polyesters back into acid
and alcohol. Carothers and his associate Julian Hill devised an apparatus
to remove the water as it formed. The result was a polyester
with a molecular weight of more than 12,000, far higher than any
Hill, while removing a sample from the apparatus, found that he
could draw it out into filaments that on cooling could be stretched to
form very strong fibers. This procedure, called “cold-drawing,” oriented
the molecules from a random arrangement into a long, linear one of great strength. The polyester fiber, however, was unsuitable
for textiles because of its low melting point.
In June, 1930, Du Pont promoted Stine; his replacement as research
director was Elmer Keiser Bolton. Bolton wanted to control
fundamental research more closely, relating it to projects that would
pay off and not allowing the research group freedom to pursue
purely theoretical questions.
Despite their differences, Carothers and Bolton shared an interest
in fiber research. On May 24, 1934, Bolton’s assistant Donald
Coffman “drew” a strong fiber from a new polyamide. This was the
first nylon fiber, although not the one commercialized by Du Pont.
The nylon fiber was high-melting and tough, and it seemed that a
practical synthetic fiber might be feasible.
By summer of 1934, the fiber project was the heart of the research
group’s activity. The one that had the best fiber properties was nylon
5-10, the number referring to the number of carbon atoms in the
amine and acid chains. Yet the nylon 6-6 prepared on February 28,
1935, became Du Pont’s nylon. Nylon 5-10 had some advantages,
but Bolton realized that its components would be unsuitable for
commercial production, whereas those of nylon 6-6 could be obtained
from chemicals in coal.
A determined Bolton pursued nylon’s practical development,
a process that required nearly four years. Finally, in April, 1937,
Du Pont filed a patent for synthetic fibers, which included a statement
by Carothers that there was no previous work on polyamides;
this was a major breakthrough. After Carothers’s death
on April 29, 1937, the patent was issued posthumously and assigned
to Du Pont. Du Pont made the first public announcement
of nylon on October 27, 1938.
Nylon was a generic term for polyamides, and several types of
nylon became commercially important in addition to nylon 6-6.
These nylons found widespread use as both a fiber and a moldable
plastic. Since it resisted abrasion and crushing, was nonabsorbent,
was stronger than steel on a weight-for-weight basis, and was almost
nonflammable, it embraced an astonishing range of uses: in laces, screens, surgical sutures, paint, toothbrushes, violin strings,
coatings for electrical wires, lingerie, evening gowns, leotards, athletic
equipment, outdoor furniture, shower curtains, handbags, sails,
luggage, fish nets, carpets, slip covers, bus seats, and even safety
nets on the space shuttle.
The invention of nylon stimulated notable advances in the chemistry
and technology of polymers. Some historians of technology
have even dubbed the postwar period as the “age of plastics,” the
age of synthetic products based on the chemistry of giant molecules
made by ingenious chemists and engineers.
The success of nylon and other synthetics, however, has come at
a cost. Several environmental problems have surfaced, such as those
created by the nondegradable feature of some plastics, and there is
the problem of the increasing utilization of valuable, vanishing resources,
such as petroleum, which contains the essential chemicals
needed to make polymers. The challenge to reuse and recycle these
polymers is being addressed by both scientists and policymakers.