Flame-retardant cotton gets a boost from clay

From Anaheim, Calif., at a meeting of the American Chemical Society

When it comes to clothing, many consumers prefer cotton to synthetic fibers.

Cotton is soft, doesn’t irritate the skin, and permits air to flow through, making it cool to wear in warm weather.

“The drawback of cotton is that it’s flammable, and therefore it can’t be used for things like children’s sleepwear,” says Leslie White, a chemist at the Agricultural Research Service’s Southern Regional Research Center in New Orleans.

So, she and her colleague David Delhom have devised a way to increase cotton’s heat tolerance with an unlikely substance: clay.

The researchers dissolved cotton cellulose in a solution and added montmorillonite clay nanoparticles. The mixture was then spun into fibers containing 93 percent cotton and 7 percent clay. To test the fibers’ heat tolerance, the researchers warmed them in a chamber and measured the weight loss. The greater the weight loss, the less stable—and therefore the less heat tolerant—the material.

The composite material’s heat tolerance was found to be 20° to 30°C greater than that of untreated cotton. White says the treated fibers spontaneously form a coat of char on their surfaces when heated. In a fire, the coating would prevent oxygen from seeping into the fibers, where it would feed flames.

White and Delhom are now beginning to weave fabrics from their clay-cotton fibers. The researchers plan to test these products for flame retardancy.