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From fiber to fabric: a better blend.

From Fiber to Fabric: A Better Blend

Agricultural Research Service scientists are re-engineering the clothes you wear. They have patented a new way to blend more cotton fiber with synthetic fiber to make yarn. These new yarns result in fabric that is strong yet comfortable, says inventory A. Paul S. Sawhney, a research cotton technologist with ARS' Fiber Quality Research Unit in New Orleans.

Typically, blend yarns are 65-percent synthetic fiber and 35-percent cotton. But a new spinning technique developed by Sawhney and co-inventors Craig L. Folk, Kearny Q. Robert, and Linda B. Kimmel changes the way blend yarn is made.

"This invention allows textile companies to make a fabric with the comfort and breathability of 100-percent cotton, without sacrificing the strength and finishing advantages of manmade fiber," says Sawhney.

Blended yarns became popular when consumer demand for 100-percent synthetic fibers like polyester and nylon decreased in the 1970's.

Consumers started choosing cotton because of its durability, comfort, and absorbency. They missed, however, the no-iron features of the synthetics. This led to the development of blends of cotton and synthetic fibers.

Blends provided the good features of both fibers and became a middle-of-the road fabric that pleased the consumer. But current blend yarns do have their disadvantages.

In fabrics made from conventional blend yarns, the cotton fiber wears and breaks off, while the synthetic fiber doesn't, says Sawhney. This can cause pilling, which is a very serious problem. "I think we have solved that problem."

Pilling - the formation of small unsightly balls - happens because synthetic fibers are stronger than cotton fibers, so they don't wear in the same way. As a result, synthetic fibers project from the surface of conventional blend fabrics.

In the invention developed at the Southern Regional Research Center in New Orleans, stronger synthetic fibers are hidden under a layer of cotton fibers and don't project out of yarn to the surface.

Currently cotton and synthetic fiber are randomly combined and wound on a bobbin called a roving. The roving bobbin is put on a spinning machine where the blended fibers and spun into yarn.

The new technology combines fibers from separate rovings that are 100-percent cotton and 100-percent synthetic, Sawhney says. A unique device is used to combine the two fibers into a composite yarn. This is known as a wrap yarn. [See illustration on facing page.]

This spinning technique typically involves the use of two cotton roving bobbins and one polyester bobbin. The three roving bobbins, with the polyester bobbin in the middle, are suspended above the spinning frame, Sawhney says.

The three rovings are spaced about one-fourth to one-half inch apart and drawn through a series of drafting rollers. When the fibers meet after emerging from the rollers, the synthetic fiber is sandwiched between the two strands of cotton fiber, creating a strong high-cotton-content yarn with nearly a 100-percent cotton surface, he says.

"It is very similar to an electrical wire or cord where metal wire is entrapped by a rubber coating," Sawhney says. "In this case, the metal wire is synthetic fiber and the rubber coating is cotton.

"Also, there is a unique interlocking of fibers that prevents stripping of the cotton sheath," Sawhney says. "The lead ends of cotton fibers from the two cotton rovings get trapped first, followed by the tail ends of the fibers spinning around the core yarn.

"Again, it's like electrical wire," he adds. "You don't want the rubber coating sliding off of a metal wire."

By segregating the cotton with the polyester in the middle, the invention enhances the benefits of both fibers while eliminating pilling. The current blend yarn has its fibers randomly scattered in the yarn, diluting the performance of each fiber.

Sawhney says the textile industry might object to the cost involved in using two cotton rovings. However, the extra expense to prepare the rovings should be more than offset by making a premium-priced yarn.

"The fabric is just more dimensionally stable," he says. "It [the invention] also gives fabric better mechanical properties of tear and tensile strengths. I think consumers will like this new cotton-rich product. It offers greater comfort and better appearance than currently available no-iron blends."

Researchers have experimented with composites as high as 90-percent cotton, but found the 65-percent cotton blend comparable to a conventionally made 65-percent synthetic blend.

The invention doesn't limit core-yarns to cotton and man-made fibers. Scientists are also experimenting with fibers like wool, mohair, and goat hair.

Also, the invention can make coarse or inferior grades of cotton more marketable because it essentially layers the coarse fiber inside the higher quality fiber, Sawhney says.

"There are also a lot of specialty yarns that could be produced using this method," Sawhney adds. "We're continuing to work on ways to improve this technology."

Ann Whitehead, coordinator of the U.S. Department of Agriculture's National Patent Program, notes that the invention is patented and available for licensing.

PHOTO : Cotton technologist A. Paul Sawhney observes the polyester staple-core/cotton-wrap spinning system, a new way to blend more cotton fiber with synthetic fiber. The yarn results in a fabric that is strong yet comfortable. (K-3855-20)

PHOTO : Cotton technologist Paul Sawhney examines a finished fabric roll of polyester staple-core/cotton-wrap. (K-3854-19)
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Title Annotation:new way to blend more cotton fiber with synthetic fiber
Author:Kinzel, Bruce
Publication:Agricultural Research
Date:Mar 1, 1991
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