The potential market for plastics compounded with carbon nanotubes (CNTs) is huge. But questions are being asked about health and safety.

A quick look at the nanocomposites world may leave the observer with the impression that it''s all talk and little action. The number of commercial applications running with nanoclays that have been made public can probably be numbered on the fingers of one hand.

So this may come as a surprise: Hyperion Catalysis (Cambridge, MA), the world''s leading supplier of multiwall carbon nanotubes (MWNTs), says that roughly 60% of all cars built in the U.S. today incorporate its product in fuel lines to stop the accumulation of static electricity. It says it has achieved this impressive market position because nanotube-containing compounds simplify production of the fuel lines (obviating complicated coextrusion) at a cost competitive with other solutions.

These nanotubes—Hyperion''s trade name is Fibrils—are also found in some compounds used for exterior body parts, enabling them to be electrostatically painted without affecting the ductility of the thermoplastic. They are also widely used in electronics for such products as hard disc drive trays and wafer carriers, where their resistance to sloughing puts them ahead of other conductive fillers like carbon black.

Hyperion does not identify specific auto products containing fibrils, and Sales and Marketing Manager Pat Collins will only say the company is talking to all major suppliers of engineering thermoplastics for fenders. GE Plastics has used Fibrils in the past, but it is not clear if it still does; in automotive applications, cost is king, and MWNTs are not cheap (over $750/kg, sources say), even though addition levels can be as low as 2%. In the meantime, Hyperion is looking to expand its portfolio (it sells its nanotubes predispersed in compounds and concentrates; it does not sell them in their pure form), and it is also looking to sell into more segments. No announcements are expected before 2005.

"We have never seen a free nanotube"

Collins says in-house compounding gets around two issues. First, nano additives are very difficult to disperse, because of the high level of Van der Waals forces holding them together. Hyperion has developed special equipment to do its compounding. Second, customers don''t have to worry about the health and safety issues that are becoming increasingly apparent in the nanotechnology world (see accompanying article). "Once nanotubes are encapsulated in plastics, they are OK," says Collins. "You can sand and grind parts, and you won''t liberate individual nanotubes."

What about health and safety precautions at Hyperion itself? "We go to great lengths to make sure there is no exposure throughout our whole setup. We have never seen a free nanotube."

Collins says the company is developing single-wall carbon nanotubes, along with numerous other companies. SWNTs have the potential to provide materials with electrical properties orders of magnitude better even than MWNTs, while also possessing better mechanical properties (December 2002 MP/MPI). Although the rewards may be great, it could be some time, however, before the potential can be actualized. For now, virtually all production is at lab scale, product costs upwards of $500/g, and there are many technical hurdles to be overcome before industrial-scale production could be widespread.

Progress is being made, though. Carbon Nanotechnologies Inc. (Houston, TX) is currently building a demonstration plant with a capacity of approximately 100 lb per day (45 kg). Company President and CEO Bob Gower expects the unit "to be in the initial shake-out mode early during the 3rd quarter. Our plan also is to build a larger unit in 2005."

According to Gower, "CNI has our products at about 400 locations around the world. Several of our customers indicate that they are close to commercial applications, including testing of products with their customers.

"We have confidentiality agreements with most of our customers and cannot discuss specifics," Gower says.

"But the application areas include flat-panel displays, electronics, electrostatic dissipation, electromagnetic shielding, high-strength composites and fibers, and fuel cells."

Single-walled tubes in production

The U.K.''s first commercial manufacturing process for high-purity SWNTs was commissioned earlier this year by performance chemicals company Thomas Swan & Co. Ltd. (Consett, England). "The availability of commercially produced carbon nanotubes of a consistent quality and at an accessible price is expected to unlock the potential for a wide range of industrial applications," says the company. It will sell Elicarb nanotubes for around $350/g. "The company is now in a position to supply kilogram orders from stock but are reserving judgment on capacity until they have run the plant for a month or so to gather accurate and meaningful data," said a representative in late April.

In February, Carbon Nanotechnolo- gies announced the issue of a patent it says "is central to the development of real-world applications of nanotechnology." It describes linking carbon nanotubes to each other and to other species and substrates, "greatly enhancing the potential of carbon nanotubes and broadly expanding their range of end uses." Richard Smalley, whose Nobel Prize-winning technology is licensed exclusively to CNI, is quoted by the company as saying "it is difficult to imagine carbon nanotechnology applications which will not be enhanced by this enabling patented technology." It can "dramatically improve" physical properties for a new class of nanocomposite products and fibers.

In April, Zyvex Corp. (Richardson, TX) introduced the first two products in its NanoSolve line of additives based on nanotubes, for polyurethanes. One is based on SWNTs, the other on MWNTs, which it sources externally. The company says the additives boost the host material''s conductivity and mechanical strength. Electrical conductivity can be boosted by 10 orders of magnitude. Zyvex envisages applications in printers, auto parts, heat pipes, flooring, and other areas. In the works are additives for other plastics, including epoxies, polycarbonate, polystyrene, and a confidential material for the U.S. military.

Zyvex has developed surface treatment technology it says allows excellent dispersion of CNTs in various solvents (including water), as well as enhancing the interaction between CNTs and the host matrix. A multifunctional "bridge" between the CNT sidewalls and the host material contains two major components. One component adheres to the nanotube; the other has the functionality to adhere to the host. Mark Banash, senior engineer for nanomaterials, says that Zyvex ''Kentera'' technology provides levels of adhesion between polymer and nanotube far higher than the cohesive forces between the nanotubes themselves. He also says that bonding is highly resistant to thermal cycling.

Zyvex is also working on a two-year NASA contract to build what it says will be a prototype of the world''s toughest material in collaboration with the Nano Tech Institute at the University of Texas at Dallas. NASA needs the new materials to help improve spacecraft, vehicle launch, and space station performance.

"It''s not a better form of carbon black"

Banash reckons the market can sustain the high prices nanotubes command. "I have turned down fairly big players in the plastics market because they thought this would be a carbon black substitute. It''s not a commodity chemical. Single-walled tubes are $500 a gram in some cases. But we are aiming for people who are early adopters of the technology; they need a competitive advantage and they need it now. We are talking about something that is used at a very low loading, a quarter of a percent in some cases, by weight. If you have a $20/lb resin and you are talking about adding $2 to the price of that, you are going to get a huge jump in performance—people can absorb that." PM

Is that a brick wall in front of the whole new ball game? First, the good news, from the executive summary of a new report by the Freedonia Group detailing the market for nanocomposites:

"The U.S. market for nanocomposites is expected to increase to 345 million pounds [158,000 tonnes] by 2008 and approach 11 billion pounds [5 million tonnes] by 2020, with a value of $37 billion. By that time, nanocomposites are expected to have partially supplanted traditional reinforced plastics in construction applications...motor vehicle parts...consumer goods such as appliances and sporting goods; in packaging materials...in electronic components and other equipment; and in high performance applications such as spacecraft and military equipment."

Now the bad news, this time from a recent report in the Washington Post:

"Studies have also shown that nanoparticles can act as poisons in the environment and accumulate in animal organs. And the first two studies of the health effects of engineered nanoparticles, published in January, have documented lung damage more severe and strangely different than that caused by conventional toxic dusts...Some in California are trying to block construction of a nanotech factory, noting that no government agency has developed safety rules for nano products. Others want a global moratorium on the field until the risks are better understood."

It is not stretching the imagination too far to envisage the nanotechnology industry running into the same brick wall as Monsanto and others did with their genetically modified (GM) crops. And while leading lights in the nano world like Mark Ratner (the author of Nanotechnology: A Gentle Introduction to the Next Big Thing) believe that lessons have been learned from the GM debacle; nano-particle producers argue that their products are safe once they are in compounds; and governments around the world are pumping millions of dollars into nanotechnology programs; political sensitivity to "What if?" scenarios cannot rule out restrictions being applied to at least some areas of nanotechnology development.

Bob Gower, president and CEO of CNI, cites a study by the U.S. government''s National Institute for Occupational Safety and Health (NIOSH), which visited the company''s facility. "They concluded that, under normal handling conditions, there were very low respirable-size concentrations developed. They concluded that this was because single-wall carbon nanotubes do not exist as individual molecules under normal conditions, but instead exist as large ropes containing a million or more individual nanotubes." Gower also cites studies "where toxicological impact was examined totally separate from the ability to get respirable-size quantities into the air. In those cases, nanotubes were injected directly into mice or rats, and abnormalities resulted. [The author] indicated that much of the effect may have been a result of the injection method and of dose level."

Dai Hayward, GM at Thomas Swan & Co. Ltd., says:

"We are making every effort to develop safe and effective methods of using carbon nanotubes and are working with others to define how the advantages of carbon nanotubes can be developed in a safe manner...The technology and market is in the early stages of development.

"In the meantime, U.K. and European law regulate the way new materials are developed through an appropriate exercise of the precautionary principle. The law currently states that carbon nanotubes are nonhazardous and similar in nature to other forms of pure carbon such as graphite and carbon black. However, we recognize the need for the full nature of carbon nanotubes to be evaluated and for all the risks to be fully understood...

"There is a big difference from the GM debate in that nanomaterials present a range of physical, quantifiable challenges for their safe use and handling, which can be understood and addressed in much the same way as all other materials. The development of GM is influenced by organic and natural influences which are potentially more random, unpredictable and less well understood."

Peter Mapleston [email protected]

Addressing consistency

Zyvex recently announced the implementation of a supply chain certification program for carbon nanotube suppliers. "Establishing a raw material standard and maintaining quality assurance to meet that standard is the key to the commercialization of carbon nanotubes and carbon nanotube-based materials," says Zyvex President Thomas A. Cellucci. According to Mark Banash, "Our analytical process objectively assesses a given CNT manufacturer''s underlying technology and production scalability. It also considers the business structure of the firm, its ability to raise capital, and its long-term commitment to the marketplace." Zyvex was expecting to certify major suppliers of multiwall and single-wall carbon nanotubes by June. Banash says he reckons that while there are "three to four dozen" companies in the world making nanotubes, there are probably no more than six capable of consistently making a quality product.

Meanwhile, Dutch firm Mo6 B.V. (Helmond) has developed MoSIx-6 as an alternative to carbon nanotubes. "One of the biggest challenges in nanotechnology is the synthesis of pure, monodispersed nanotubes or nanowires with identical structure and, ideally, tuneable physical or functional properties," says Dragan Mihailovic, chief scientist of Mo6, "but the prototype material—carbon nanotubes—stops short of fulfilling this goal, partly because it is difficult to synthesize CNTs in a way that produces identical nanotubes in bulk.

One-dimensional "molybdenum cluster polymers" are said to surpass many of the synthesis-related shortcomings of carbon nanotubes, while their functional properties, such as mechanical strength, electrical conductivity, and field emission characteristics, are very similar to carbon nanotubes. Pricing is—wait for it—€2000 to €4000/g, "with volume discounts." PM

Made in Japan?

"Several firms have capacity for commercial quantities of MWNTs in Japan, but two factors are limiting market penetration of nanocomposites there— quality issues and extensive application patent coverage held by Hyperion." That''s the view from Toru Kawasaki, President of Kawasaki Techno Research, Osaka.

He says it is important that CNTs are of uniform size to enable uniform dispersion throughout the resin matrix, but this is proving difficult to achieve. He adds that potential users are put off by the prospect of legal action from Hyperion if they use carbon nanotube-based composites in commercial applications.

One Japanese supplier is Nikkiso Co. (Tokyo), with annual capacity estimated at between 20 and 40 tonnes. Kawasaki says Nikkiso claims prior submission of patents covering CNT application, and is battling Hyperion in the U.S. courts. Nikkiso has lost court cases twice, and is appealing for the second time.

Hyperion''s application patents cover the use of CNTs of diameters less than 80 nm, a critical dimension below which conductive properties are maximized, says Kawasaki.

"Anything above this and the advantages over conventional carbon fibers are minimal," he says. Suppliers such as Showa Denko (Tokyo; 40 tonnes/yr capacity) and Nikkiso currently only offer CNTs with diameters of 80 nm or more. Showa Denko, for example, offers the VGCF (Vapor Grown Carbon Fiber) electrically/thermally conductive material for use in resins.

Japanese trading houses have invested heavily in CNTs with little to show yet [for the reasons stated above]. The XNRI Group at Mitsui & Co. (Tokyo) has a facility at Akishima, near Tokyo, rated at 120-tonnes/yr, but output is understood to be very low.

Sumitomo Corp. (Osaka) is another trading house with significant CNT capacity (150 tonnes/yr). It recently licensed patents from NEC. It also signed an exclusive marketing and distribution agreement for CNI''s SWNTs in Japan and South Korea, and has taken a financial stake in CNI. Stephen Moore