14 October 2009
The invention: The first totally synthetic thermosetting plastic,
which paved the way for modern materials science.
The people behind the invention:
John Wesley Hyatt (1837-1920), an American inventor
Leo Hendrik Baekeland (1863-1944), a Belgian-born chemist,
consultant, and inventor
Christian Friedrich Schönbein (1799-1868), a German chemist
who produced guncotton, the first artificial polymer
Adolf von Baeyer (1835-1917), a German chemist
Exploding Billiard Balls
In the 1860’s, the firm of Phelan and Collender offered a prize of
ten thousand dollars to anyone producing a substance that could
serve as an inexpensive substitute for ivory, which was somewhat
difficult to obtain in large quantities at reasonable prices. Earlier,
Christian Friedrich Schönbein had laid the groundwork for a breakthrough
in the quest for a new material in 1846 by the serendipitous
discovery of nitrocellulose, more commonly known as “guncotton,”
which was produced by the reaction of nitric acid with cotton.
An American inventor, John Wesley Hyatt, while looking for a
substitute for ivory as a material for making billiard balls, discovered
that the addition of camphor to nitrocellulose under certain
conditions led to the formation of a white material that could be
molded and machined. He dubbed this substance “celluloid,” and
this product is now acknowledged as the first synthetic plastic. Celluloid
won the prize for Hyatt, and he promptly set out to exploit his
product. Celluloid was used to make baby rattles, collars, dentures,
and other manufactured goods.
As a billiard ball substitute, however, it was not really adequate,
for various reasons. First, it is thermoplastic—in other words, a material
that softens when heated and can then be easily deformed or
molded. It was thus too soft for billiard ball use. Second, it was
highly flammable, hardly a desirable characteristic. Awidely circulated, perhaps apocryphal, story claimed that celluloid billiard balls
detonated when they collided.
Since celluloid can be viewed as a derivative of a natural product,
it is not a completely synthetic substance. Leo Hendrik Baekeland
has the distinction of being the first to produce a completely artificial
plastic. Born in Ghent, Belgium, Baekeland emigrated to the
United States in 1889 to pursue applied research, a pursuit not encouraged
in Europe at the time. One area in which Baekeland hoped
to make an inroad was in the development of an artificial shellac.
Shellac at the time was a natural and therefore expensive product,
and there would be a wide market for any reasonably priced substitute.
Baekeland’s research scheme, begun in 1905, focused on finding
a solvent that could dissolve the resinous products from a certain
class of organic chemical reaction.
The particular resins he used had been reported in the mid-
1800’s by the German chemist Adolf von Baeyer. These resins were
produced by the condensation reaction of formaldehyde with a
class of chemicals called “phenols.” Baeyer found that frequently
the major product of such a reaction was a gummy residue that was
virtually impossible to remove from glassware. Baekeland focused
on finding a material that could dissolve these resinous products.
Such a substance would prove to be the shellac substitute he sought.
These efforts proved frustrating, as an adequate solvent for these
resins could not be found. After repeated attempts to dissolve these
residues, Baekeland shifted the orientation of his work. Abandoning
the quest to dissolve the resin, he set about trying to develop a resin
that would be impervious to any solvent, reasoning that such a material
would have useful applications.
Baekeland’s experiments involved the manipulation of phenolformaldehyde
reactions through precise control of the temperature
and pressure at which the reactions were performed. Many of these
experiments were performed in a 1.5-meter-tall reactor vessel, which
he called a “Bakelizer.” In 1907, these meticulous experiments paid
off when Baekeland opened the reactor to reveal a clear solid that
was heat resistant, nonconducting, and machinable. Experimentation proved that the material could be dyed practically any color in
the manufacturing process, with no effect on the physical properties
of the solid.
Baekeland filed a patent for this new material in 1907. (This patent
was filed one day before that filed by James Swinburne, a British electrical engineer who had developed a similar material in his
quest to produce an insulating material.) Baekeland dubbed his new
creation “Bakelite” and announced its existence to the scientific
community on February 15, 1909, at the annual meeting of the American
Chemical Society. Among its first uses was in the manufacture
of ignition parts for the rapidly growing automobile industry.
Bakelite proved to be the first of a class of compounds called
“synthetic polymers.” Polymers are long chains of molecules chemically
linked together. There are many natural polymers, such as cotton.
The discovery of synthetic polymers led to vigorous research
into the field and attempts to produce other useful artificial materials.
These efforts met with a fair amount of success; by 1940, a multitude
of new products unlike anything found in nature had been discovered.
These included such items as polystyrene and low-density
polyethylene. In addition, artificial substitutes for natural polymers,
such as rubber, were a goal of polymer chemists. One of the results
of this research was the development of neoprene.
Industries also were interested in developing synthetic polymers
to produce materials that could be used in place of natural fibers
such as cotton. The most dramatic success in this area was achieved
by Du Pont chemist Wallace Carothers, who had also developed
neoprene. Carothers focused his energies on forming a synthetic fiber
similar to silk, resulting in the synthesis of nylon.
Synthetic polymers constitute one branch of a broad area known
as “materials science.” Novel, useful materials produced synthetically
from a variety of natural materials have allowed for tremendous
progress in many areas. Examples of these new materials include
high-temperature superconductors, composites, ceramics, and
plastics. These materials are used to make the structural components
of aircraft, artificial limbs and implants, tennis rackets, garbage
bags, and many other common objects.