Nanotube production set for growth

Small wonder

17 June 2009 00:00  [Source: ICB]

Carbon nanotubes might finally be on the verge of commercial success, as major manufacturers announce plans to ramp up production

Lou Reade/London

IF SMALL is beautiful, that's certainly true for carbon nanotubes (CNTs) - a breed of additive that is improving a range of plastics products, from automotive parts to surfboards.

CNTs and other nanoparticles - an order of magnitude smaller than conventional plastics fillers - can have dramatic effects on properties when compounded into a polymer: packaging films admit less oxygen; composites are stronger and lighter; and electronics products can be rendered antistatic.

Most CNT production has been in pilot-scale operation, but that is changing. German chemical firm Bayer has begun work in Leverkusen to increase the production of its Baytubes from 60 to 200 tonnes/year. (Its eventual aim, by 2013, is to produce 3,000 tonnes/year. Sun Nanotech, a leading Chinese producer, is seeking finance for a 100 tonne/year plant.

Similarly, French chemical company Arkema plans to upgrade its plant in Lacq, France, from 20 to 200 tonnes/year next year. There are also suppliers in the US, India and Japan. And with several high-profile commercial applications coming on stream, it seems that CNTs have finally made it out of the lab and into the real world.

"The world market for nano-materials is around $1.5bn (€1bn), and I think this will double over the next two to three years," says Krzysztof Grzybowski, an analyst at US consultancy Frost & Sullivan.

But he says it is difficult to predict future market size because, while production will continue to grow, prices are likely to come down. "At last year's major nanotechnology event in Tokyo, the price of CNTs was $80-100/kg," he says. "This year, the price is $45-70/kg, depending on quality. At the same time, Chinese manufacturers can offer CNTs at lower prices."

Arkema markets its CNTs under the name Graphistrength. It recently developed a universal masterbatch - containing 30% CNTs by weight - that can be compounded into resins, including polycarbonate (PC), polyester and polyamide to impart antistatic properties. It has also developed a specific grade for fluoro-elastomers.

Arkema has also begun European distribution of a range of CNT-enhanced epoxy resins from US-based nanotechnology company Zyvex, showing the increasing importance of the composites market to CNT suppliers.

"Carbon nanotubes open up tremendous possibilities in the field of lightweight construction," says Martin Schmid, general manager carbon nanotubes at Baytubes - Bayer's CNT business.

An example is rotor blades for wind turbines, which are often of limited length because of their weight. Blades made from CNT-based fiberglass-reinforced epoxides would be up to 30% lighter - and much stronger - than conventional epoxy systems. Bayer claims a 20-30% improvement in impact strength, for example.

"Rotor blades made of this new composite material can be made longer, which raises the output of wind power plants," he says.

Bayer boasts another application for CNT-based epoxy: a custom-made surfboard from US-based Entropy Surfboards that makes the epoxy tougher while retaining flexibility. "The carbon nanotubes increase durability by a factor of two to three, while decreasing the fatigue often seen in traditional boards," says Rey Banatao, head of bio-based material development and sourcing at Entropy. "We decided to use carbon nanotubes in our products once they became available and affordable."

Fueling growth
Plastics giant BASF of Germany has launched its first CNT-based resin. The material, Ultraform N2320C, has a relatively high level of electrical conductivity - yet retains the usual toughness of an acetal. Germany-based automotive Tier 2 supplier Bosch is using the material to make a fuel filter housing for the Audi A4 and A5.

"The main challenge was meeting Bosch's requirements in terms of electrical conductivity and - at the same time - mechanical properties, especially toughness," says Juergen Demeter, technical product manager for Ultraform. The increased surface conductivity - 30,000 times higher than for earlier versions of the housing - helps Audi meet standards set by the US Society of Automotive Engineers, which aims to prevent sparks in the region of components that carry fuel.

To date, many antistatic plastics have used carbon black as a filler. But the aspect ratio of CNTs - the ratio of length to thickness - means that the same effect can be delivered using far less additive. CNT loading for the Bosch component is less than 5%. For a carbon black compound, it would need to be at least 20%. This lower loading ensures that the material retains more of its "acetal-like" mechanical behavior.

BASF believes that further applications for the material exist in the microelectronics and conveying industries. And it is looking to move beyond a single type of plastic.

The company is a partner in the CNT Innovation Alliance, which numbers around 80 industry and academic partners. Between them, they have poured an estimated €80m ($111m) into CNT research - and most of them are looking to make a return.

Another potential application, which has been largely ignored, is that of flame retardancy. While CNTs alone cannot replace conventional flame retardants, Grzybowski says that small amounts of CNT can have a significant effect.

He believes that flame retardancy has been ignored because it does not fit with the sophisticated image of CNTs. With the world flame retardant market estimated at $3bn (€2bn) - and products in every industry subject to some kind of fire regulation - he believes this is a potentially lucrative market.

"There are not yet any applications of CNTs as flame retardants," he says. "But if the prices keep going down, it could happen."

WHAT ARE CARBON NANOTUBES?
Carbon comes in many forms, with graphite and diamonds being the best known. Carbon nanotubes (CNTs) are simply another molecular arrangement of carbon. Most are produced industrially by chemical vapor deposition (CVD) and - as the name suggests - take the form of tiny tubes. These can be single-walled (difficult to make, and very expensive), double-walled, and multi-walled - the most common variety.

While other nanoparticles - such as nanoclays - are more established, carbon nanotubes are likely to be more versatile and deliver a broader range of properties - especially for antistatic applications. Aside from being used as a plastics additive, CNTs may have use in fuel cells, lithium-ion batteries and drug delivery.

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