Stopping wool from shrinking

From San Diego, at a meeting of the American Chemical Society

You accidentally toss your favorite wool sweater into the wash, and it reemerges toddler size. To prevent such accidents, scientists in Austria have created an enzyme treatment to protect wool clothes from shrinkage.

Wool fibers are composed of keratin proteins bundled into microfibrils. The fibrils are wrapped in a natural scaly cuticle. When wool is washed, the scales interlock, preventing the fibers from moving freely. This interlocking prevents the fabric from retaining its original size.

There already are shrink-proofing treatments for wool, but they rely on chlorine-based chemicals to remove the cuticle and, as a result, generate wastewater that can be harmful to the environment.

Angelika Erlacher and her colleagues at the Graz University of Technology in Austria decided to find an environmentally friendly route to unshrinkable wool. The team discovered an enzyme in the soil fungus Beauveria brongniartii that degrades wool fibers. To ensure that the enzyme wouldn’t attack the protein fibrils, the researchers attached it to a large polymer that can’t penetrate the cuticle. They then soaked the fabric with the polymer-enzyme complex and, after it had partially degraded the cuticle and smoothed it out, washed away the complex.

After subjecting their shrink-proof wool textiles to several washing cycles, the Austrian group found that the treated wool didn’t loose any of its volume and was virtually indistinguishable from unwashed textiles. In contrast, untreated fabrics with the same wash regimen were reduced to about half their original size.

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