?? JEC History - THE SECOND MATERIALS BREAKTHROUGH: CARBON FIBERS (1959-1969)

?? JEC History - THE SECOND MATERIALS BREAKTHROUGH: CARBON FIBERS (1959-1969)

THE SECOND MATERIALS BREAKTHROUGH: CARBON FIBERS (1959-1969) - Episode 5

In the late 1950s and early 1960s breakthroughs in carbon fiber research occurred in Japan, the UK and the USA. All the researchers contributed in one way or another; they had mutual contacts and even inspired and motivated each other.

Preparatory research

When Akio Shindo joined the Government Industrial Research Institute in Osaka (GIRIO) in Japan in 1952, he was assigned to the carbon R&D division. Shindo later described the research as follows: “The degradation of carbon is not necessarily a bad theme depending on the method of research, but it seems that it is unlikely that a fruitful result can be expected from the viewpoint of the development of industrial materials.”

After World War II, the US National Carbon Company explored the use of rayon and other fibers to replace tungsten in vacuum tube power amplifiers. In 1957, the Barnebey-Cheney company manufactured mats and tows by carbonizing cotton and rayon fibers for thermal insulation and filter applications. A year later, Union Carbide developed a carbonized rayon cloth for the US Air Force as a replacement for fiberglass in rocket nozzle exit cones and re-entry heat shields. William F. Abbott at the Carbon Wool Corp seems to have started research on carbonizing rayon fibers in the mid-1950s, but he did not file his patent until 1959.

A breakthrough occurred in 1958 at Union Carbide’s Parma Technical Centre, when Roger Bacon succeeded in making carbon whiskers. It was now proven that ‘carbon’ could reach a Young’s modulus of 700 GPa and a strength of 20,000 MPa. These were discontinuous fibers, produced in laboratory experiments, and Bacon estimated the cost at US$20 million per kilogram. Bacon published his results in 1960.

In 1959, one year after Bacon’s discovery, Ford and Mitchell carbonized, in the same lab, rayon fibers at temperatures up to 3000°C, achieving much higher strengths (up to 900 MPa) than those of commercial lamp filaments (200 MPa). These superior properties were mainly a result of a much smaller fiber diameter. It was a further step in the development of carbon fibers from cellulose-based (rayon) precursors, but it was another five years until Bacon and Schalamon were able to produce high modulus carbon fibers from rayon by stretching them during the heating process.

Shindo’s pioneering work on PAN fibers

As far as is known, Akio Shindo was not aware of Bacon’s developments, but his attention is said to have been drawn to the National Carbon Company’s early developments on carbon felt and fabrics in May 1959 by an article in a Japanese newspaper. This referred to an article in US magazine Machine Design of 30 April 1959. In this, a brief description of “the method to thermochemically process fibers such as rayon to graphite by heating at 3000°C“ was presented, most probably pointing to Ford and Mitchell’s research at Union Carbide. It inspired him to focus on the use of polymeric precursor fibers, and on 7 September 1959 he filed his patent on using polymeric fibers (PAN only) as precursor for carbon fibers.

Shindo’s patent was published in 1962, but he had already presented some results at a domestic conference in October 1959, and in 1961 the famous GIRIO report n° 317 was published where, according to one source, a fiber stiffness of 110 GPa was reported without mentioning the heat treatment temperature. In 1961 and 1962 he published several papers in Japanese journals, but he also presented his research during the 6th American Carbon Conference in USA in 1963.

First attempts towards commercialization in Japan in the early ‘60s

According to a WIPO paper, Shindo’s patent was licensed in 1963 to two Japanese companies, Nippon Carbon and Tokai Denkyoku (now Tokai Carbon). A Japanese source states that Nippon Carbon signed a research contract with Shindo and in 1961 introduced the first commercial carbon fiber Carbolon at a cost of 30,000-50,000 Yen (per kg), with a tensile strength of 1000 MPa. Two years later, Tokai Denkyoku launched the Thermolon fiber. Both fibers were mainly aimed at high temperature applications.

Who discovered that tensioning the fibers creates orientation of the graphite?

The orientation of the graphite molecular units became a crucial point in further improvements of the stiffness (and strength) of carbon fibers. But where did this idea come from? Was it Shindo in Japan, who had already applied a “strain” during the oxidation treatment of the PAN fibers (1959)? Was it in the UK, where Watt, Johnson and Phillips at RAE realised a breakthrough in their work on (a different kind of) PAN fibers (1964)? Or in the US, where Kotlensky et.al. were first to study systematically the effect of straining on pyrolytically deposited graphite (1962), followed by the study of Bacon et al. in restraining rayon-based carbon fibers (UCC, 1964, 1969)?

It's unclear to what extent Watt, Johnson and Phillips were inspired by the work of Shindo or Kotlensky, Bacon and colleagues. In June 1963, Watt is reported to have told a colleague that he could make “stiff graphite fibers.” It seems that soon after this, Watt and Johnson were able, in a batch process, to produce stiff carbon fibers (up to 375 GPa modulus) by applying tension during the oxidative stabilization process. Their patent was filed in April 1965. Whereas Shindo’s carbon fibers attained a maximum stiffness of 165 GPa, Watt’s fibers reached up to 400 GPa.

Leslie Phillips showed that these fibers were compatible with epoxy and polyester resins and suggested the use of Courtaulds’ PAN fibers as precursor. The process, patented in 1965, was licensed to three UK companies: Courtaulds, Morganite, and Rolls-Royce.

The importance of orientation was, in 1962, also proven by Kotlensky, Titus and Martens in their work on carbon fibers composed of carbon substrates with a pyrolytically deposited graphite layer. They could, by stretching up to 16% at 2750°C, increase the modulus from 16 GPa to 560 GPa. Bacon and Smith in 1964 had produced carbon fibers from rayon by stretching them at a temperature of 2800°C, leading to only a stiffness increase of 19%. In a 1969 publication, Bacon and Schalamon improved the process further, by stretching during heating, reaching a modulus of 110 GPa (at 10% stretch) to 450 GPa (at 50% stretch).

Second wave of commercialization (1965-1975)

Two hurdles still had to be overcome. Could the oxidation cycle time be reduced? Could a continuous process replace the batch type processes?

In 1966, Toray had started production of nylon 66 and Morita had researched using aniline in an innovative process to make it. This led, in 1968, to patenting a new PAN compound, which would reduce the oxidation time by a factor of 10. Toray produced PAN fiber with this new compound and delivered it to Nippon Carbon and Tokai Carbon. But Morita also encouraged the in-house commercialization of the invention. Initially, they used a batch process but Toray had no experience in high temperature treatments and so it started a collaboration with UCC in USA. J. Matsui joined Toray’s carbon fiber team, having built up experience in Toray’s tyre cord research, and was not impressed by UCC’s technology. It was then that Toray decided to acquire the “practicable rights” on Shindo’s patent in 1970 (and the rights on Nippon Carbon and Tokai Carbon’s developments) and to start their own industrial production of PAN-based carbon fibers in Japan. Toray had already opened a carbon fiber research lab in 1961 and had its own PAN fiber production. In June 1970, it was decided to invest in a production plant at Shiga with a capacity of 1 ton/month. In 1971, Toray produced 300 kg/month of Torayca T200 and T300 (continuous fiber) at a price of 95,000 Yen/kg (about 270 US$/kg). Morganite’s discontinuous fibers (1 m long) cost about 2,500 €/kg.

This was a daring decision at the time since demand for carbon fibers was low. Fortunately, Toray used the sales capacity of UCC in the USA to commercialize their carbon fibers for use in golf club shafts, and in 1973 Gay Bowers won the Pacific Ocean Masters, leading to a dramatic increase in demand and justifying a capacity upgrade to 5 tons/month.

According to an ACS paper, Union Carbide started production of Thornel 25, a rayon-based carbon fiber with a stiffness of 25 million psi (175 GPa), in 1965. But the US had no domestic PAN-based carbon fiber technology. In the same year, Boeing is reported to have asked Nippon Carbon to produce carbon fibers for them, which resulted in the Carbolon Z-1 fiber in 1969. About the same time, Tokai Carbon collaborated with the US Air Force, leading to production of the Thermolon S fiber.

It's not certain at what stage the batch type process, both for PAN- and for rayon-based carbon fibers, was replaced by a continuous process. With Toray in Japan and Courtaulds in the UK, two fiber processing companies entered the carbon fiber race, but it’s unclear when the switch from batch to continuous processes occurred. One publication refers to a 1967 publication by Ezekiel and Spain in which stretching was realised by a differential unwinding and rewinding of the (rayon-based) fibers, so they might have been the first to apply a well-known technique of continuous (polymeric) fiber stretching to carbon fibers. As mentioned earlier, Toray produced PAN-based carbon fibers in a continuous process from 1971. Rolls-Royce was also very active. That the development of a continuous process was crucial is highlighted by the fact that Rolls-Royce filed three consecutive patents: a Belgian patent in March 1966 on using Courtaulds’ Courtelle fibers, a French patent in September 1969 on oxidation under controlled tension, and a German patent in November 1969 on a continuous process with “carbon fiber sheets.” Rolls-Royce is reported to have been able to increase production from 1 tons/year with a batch process in 1967 to 25 tons/year in a continuous process in 1969.

Similar production increases were realised by Toray in Japan. In November 1972 one line at the Ehime plant had a capacity of 5 tons/month (60 tons/year). By adding a second line, and further improvements of the line, a capacity of 35 tons/month (420 tons/year) was reached in 1974.

In the US in the early ‘70s, several companies started producing carbon fibers: Hercules in 1972, Toho Rayon in 1973 (Besfight PAN-based carbon fibers, transferred/licensed to Celanese, USA, in 1978), Mitsubishi Rayon used Courtaulds’ know-how to start production in 1976, and finally Toray transferred/licensed its PAN carbon fiber technology to Union Carbide in 1978. In the 1980s, Toray started carbon fiber production in France (Soficar) and Toho Rayon in Germany (ENKA).

Developments also took place in other regions. A Russian patent describing the use of PAN fibers when carbonizing a weave, to create “a flame-retardant material with good mechanical properties,” was filed in March 1960 and probably the start of the development of carbon fibers in the Soviet Union. Several books also refer to fundamental studies on carbon and carbon fibers in France and French and German patents for both rayon- and PAN-based carbon fibers. An overview of available carbon fibers in a 1984 book includes carbon fibers produced in France (Rigilor by Le Carbone Lorraine) and Germany (Sigrifil by Sigri).

?Continue your journey into history with our celebration of 50 Years of Composites :?https://www.jeccomposites.com/about-composites/

?Next episode discusses THE ENABLING THEORETICIANS AND THE EVOLVEMENT OF “ORGANIZED COMMUNICATION” ABOUT COMPOSITES (1960-1980).?

Benedikt Borchert

Commercializing innovation! Off-the-shelf COPVs. Composites for space and aviation.

2 年

Super interesting read. Thanks for putting that timeline together :)

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