Carbon nanotubes offer potential as flame retardants

Paul Boughton

Scientists and researchers are discovering that carbon nanotubes (CNTs) could be more affordable and useful to many industrial areas, including flame-retardant materials. The global market for flame-retardant chemicals is valued at just under $3billion, with demand for non-flammable products ever-increasing. The compound annual growth rate of this market is estimated at 4 to 5 per cent for the total market up to 2015. There will be stable demand in established markets such as North America and Europe. As of 2006, the North American market was valued at $780million and the European market was valued at $762million. Based on analysis, Frost & Sullivan believes there are growing market opportunities for carbon nanotubes as a flame-retardant material.

Krzysztof Grzybowski, Frost & Sullivan analyst for the company's Technical Insights group, states: "Now, CNTs are perceived as promising additives even in flame-retardant solutions. Based on our market recognition we are assuming that phosphorous-based flame retardants will be the best market for carbon nanotubes as a flame-suppressing agent to pursue in the future. Decreasing price of this additive will be accompanied by improvement in carbon nanotubes 'know how' with developers and end users' awareness about their beneficial features."

Of the three types of nanotubes (single-, double- and multi-walled particles), single-walled particles are judged by scientists to offer the greatest potential. However, multi-walled carbon nanotubes (MWCNTs) are the most reasonable ones for commercialisation as a composite additive or coating element. They can be produced on a high scale at a relatively low price.

Originally costing about $1000 per gram (for single-walled nanotubes), MWCNTs can now be mass produced for only $100 per kilogram, depending on the shipping. This price is expected to decrease to about $10-20/kg in a few years. New technological developments in nanotube fabrication will increase production capabilities. Bayer Materials has announced plans of increasing production capacity of MWCNTs from 60 tonnes per year in 2007 to 3000 tonnes per year by the end of 2012. With plans like this in place, commercial industries will no longer find cost a deterrent.

Carbon nanotubes are now being incorporated in various materials as an agent providing non-flammability to products and coating layers. As a flame-retardant additive, MWCNTs result in stronger and more fatigue-resistant materials. MWCNTs also benefit materials' electrical properties.

The need for fire-resistant materials is rising. Current regulations are forcing producers from the household sector, electronics, building and construction, transportation, and many others to meet increasingly stringent standards of fire safety. Commercialised products that benefit from flame retardants include plastic enclosures for consumer electronics, printed circuit boards, wire and cable, electrical connectors, foam insulation, foam seating in furniture, automobiles and textiles.

CNTs are more sought after than carbon nanofibres because CNT particles provide non-flammability in relatively small concentrations compared to the other fillers. This, in effect, makes CNTs less visible and less noticeable by end users. CNTs increase nonflammability while enhancing material strength or providing an electrostatic discharge effect.

The only major hurdle left is to ensure homogenous dispersion of CNTs for maximum benefit. To ensure the quality of their products, current CNT producers are often selling them in the convenient form of master batches that help end users to take full advantage of CNTs.

For more information, visit www.frost.com

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