Polymer scientists at Cornell University believe it may soon be possible to produce a low cost, high-value, high-strength fibre from a biodegradable and renewable waste product for air filtration, water filtration and agricultural nanotechnology.

The recently-perfected technique of electrospinning to spin nanofibres from cellulose will make this achievable, according to Margaret Frey, an assistant professor of textiles and apparel at Cornell.

"Cellulose is the most abundant renewable resource polymer on earth," she said. "It forms the structure of all plants, and although researchers have predicted that fibres with strength approaching Kevlar could be made from this fibre, no one has yet achieved it. We have developed some new solvents for cellulose, which have allowed us to produce fibres using the technique known as electrospinning."

The technique of electrospinning cellulose on the nanoscale was successfully used for the first time a few months ago. It involves dissolving cellulose in a solvent, squeezing the liquid polymer solution through a tiny pinhole and applying a high voltage to the pinhole.

The technique relies on electrical, rather than mechanical forces to form fibres, and as a result, special properties are required of polymer solutions for electrospinning, including the ability to carry electrical charges. The charge pulls the polymer solution through the air into a tiny fibre, which is collected on an electrical ground.

The fibre produced is less than 100 nanometers in diameter - 1,000 times smaller than in conventional spinning.

The new technique is now possible because of a new group of solvents that can dissolve cellulose – the Cornell researchers are currently using experimental solvents to find one that will produce fibres with superior properties.

Whenever cotton is converted to fabric and garments, fibre (cellulose) is lost to scrap or waste. At present it is largely discarded or used for low-value products, such as cotton balls, yarns and cotton batting.

"Producing a high-performance material from reclaimed cellulose material will increase motivation to recycle these materials at all phases of textile production and remove them from the waste stream," said Ms Frey, adding that electrospinning typically produces nonwoven mats of nanofibres, which could provide nanoscale pores for industrial filters.

"Producing ultra-small diameter fibres from cellulose could have a wide variety of applications that would exploit the enormous surface area of nonwoven mats of nanofibres and the possibility of controlling the molecular orientation and crystalline structures of nanoscale fibres."

If successful, possible applications might include air filtration, protective clothing, agricultural nanotechnology and biodegradable nanocomposites.

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Another application the Corbell research team foresees is using the biodegradable electrospun cellulose mats to absorb fertilizers, pesticides and other materials. These materials would then release the materials at a desired time and location, allowing targeted application..

The USA produces 20 million 480-pound bales of fibre a year - world annual production is 98 million bales. At every step in the process of converting harvested cotton to fabric and garments, some fibre is lost to scrap or waste. In opening and cleaning, for example, 4 to 8% of the fibre is lost, up to 1% is lost during drawing and roving, and up to 20% during combing and yarn production.

Future Materials - December 2003