New spin on an old fiber.

Abstract

Every year, cotton growers in the United States produce 20 million bales—some 9.6 billion pounds—of cotton fiber, or about one-fifth of total global production. The great majority of this fiber is destined for use in cloth, yet more than a quarter may never reach the fabric market: at each step throughout the production process, from harvesting the puffy white cotton bolls to weaving the cloth for the shirt you’re wearing as you read this, some portion of the fiber is lost to scrap or waste. Now a Cornell University researcher has developed a new process for electro-spinning waste cotton into nanofibers using a less harmful solvent, a change that could both profit the cotton industry and afford environmentally friendly applications. According to Margaret Frey, an assistant professor of textile science at Cornell, some 4–8% of cotton fiber is lost at the textile mill in so-called opening and cleaning, which involves mechanically separating compressed clumps of fibers for removal of trapped debris. Another 1% is lost in drawing and roving—pulling lengths of fiber into longer and longer segments, which are then twisted together for strength. An average of 14–20% more is lost during combing and yarn production. Typically, waste cotton is used in relatively low-value products such as cotton balls, yarn, and cotton batting. Cotton is 90% cellulose—a very pure source of this fiber. Perhaps, Frey theorizes, more productive use could be made of this waste cotton. “My idea,” she says, “was to . . . give the industry a way to produce some high-end products.” Frey’s process involves dissolving the cotton with ethylene diamine, a relatively benign solvent, and using an electrospinning process to produce fibers 100 times smaller than anything obtainable by conventional spinning technologies. In electrospinning, a polymer solution is pulled by an arcing electrical charge through the air and onto an electrical ground. Electrospun materials can then be incorporated into a traditionally woven product to add strength or durability. Frey says the great thing about nanofibers is that they have a very high surface-to-volume ratio, so much less material will accomplish more. For example, she says, adding no more than 0.1 gram of nanofiber material per square meter to conventional filter material—for example, in a biohazard suit or air filter—will dramatically improve the efficiency of the filter. “The military can also use it in protective systems for soldiers at risk from chemical or biological weapons,” Frey says. “The tremendous filtration capabilities can protect personnel without making them feel like they’re wrapped in plastic.” Frey also suggests that these fibers could be made into mats that could absorb fertilizers, pesticides, and similar substances, later releasing them in a timed, targeted fashion.