The danger of polyester-cotton blends.

The danger of polyester-cotton blends

A chemist at the University of California at Davis reports that some polyester-cotton-blend clothing can burn "up to 25 percent faster' than clothing made either from pure synthetics such as polyester or from pure "cellulosic' fibers such as cotton or rayon. "Lightweight polyester-cotton blends, in certain apparel uses, are very dangerous,' says researcher Howard L. Needles. Moreover, he notes that while a pure synthetic will melt and fall away from the body as it burns--tending to self-extinguish --the blends hold together, giving flames and heat a greater chance of causing body burns. As a result, he feels that lightweight blends--those weighing less than 4 ounces per square yard--are inappropriate for some clothing, particularly for children or the elderly. As a substitute, he recommends pure polyester.

Despite previous research suggesting that polyester-cotton blends should be less flammable than pure cotton, these blends have been involved in a disproportionate number of clothing fires, he notes. The primary reason, his research now suggests, is that when textile makers move from producing pure cottons to making a blend, they tend to reduce the weight of the fabric. And his studies show that fabric weight per square yard is the largest factor affecting flammability.

However, Needles and his co-worker, Cynthia Walker, were able to show differences even between fabrics of the same weight. For example, they found that pure cellulosic fabrics are somewhat less flammable than polyester-cellulosic blends of the same weight. One reason, they say, may be that as the polyester melts, "it wicks and spreads' burning temperatures quickly over the cotton, enhancing the flame front's spread. Even among cellulosic fabrics they found flammability differences. Pure rayon burns faster than an equal weight of pure cotton, and polyester-rayon blends burn faster than polyester-cotton blends of the same weight.

Needles criticizes the way fabrics are tested for flammability in the United States. "If the test fabric doesn't ignite after being exposed to a flame for one second, it passes,' he says. "That really only excludes "torch' fabrics, those that practically explode when they're lit.' Even tissue paper passes that test, he notes. At least as important as ignition time, he believes, is how fast a fabric burns in the vertical position--a factor not now considered in these tests.

Another major factor affecting flammability is apparel design. "You don't hear about a tight-fitting dress shirt engulfing someone in flames,' Needles says. "It's always . . . something that's loose and gives a good air-fabric mix that spreads flames around the body,' he says.