Polyacrylonitrile: a concurrent
researchers in the United States were reveling in rayon, scientists overseas
were busy creating their own carbon fiber industries based on polyacrylonitrile,
or PAN, which had been passed over by U.S. producers after unsuccessful
attempts at making high modulus fibers.
A quiet study by Japanese researchers in 1961 — largely unknown
to Western scientists — demonstrated high strength and high modulus
fibers from PAN precursors. Akio Shindo of the Government Industrial Research
Institute in Osaka, Japan, made fibers in the lab with a modulus of more
than 140 GPa, about three times that of rayon-based fibers at the time.
Shindo’s process was quickly taken up by other Japanese researchers,
leading to pilot-scale production in 1964. In that same year, just a few
months before Bacon and Schalamon debuted their hot-stretching method,
William Watt of the Royal Aircraft Establishment in England invented a
still higher-modulus fiber from PAN. The British fibers were rapidly put
into commercial production.
The secret behind these developments was better precursors. In both Japan
and England, researchers had access to pure PAN, with a polymeric backbone
that provided an excellent yield after processing. The continuous string
of carbon and nitrogen atoms led to highly oriented graphitic-like layers,
eliminating the need for hot stretching. Chemical manufacturers in the
United States, however, generally inserted other compounds in the polymer
backbone that could account for up to 20 percent of the product, making
them totally unsuitable for carbonizing.
The Japanese eventually took the lead in manufacturing PAN-based carbon
fibers, effectively beating the British at their own game. Japan’s
Toray Industries developed a precursor that was far superior to anything
seen before, and in 1970 they signed a joint technology agreement with
Union Carbide, bringing the United States back to the forefront in carbon
PAN-based fibers eventually supplanted most rayon-based fibers, and they
still dominate the world market. In addition to high modulus fibers, British
researchers in the mid-1960s also developed a low modulus fiber from PAN
that had extremely high tensile strength. This product became widely popular
in sporting goods such as golf clubs, tennis rackets, fishing rods, and
skis; it is also extensively used for military and commercial aircraft.