A specially treated cotton fabric can actively extinguish flames when it is set on fire.

Credit: WILEY-VCH

The material was produced by Jaime Grunlan at Texas A&M University in College Station and his colleagues by dipping the fabric repeatedly into two different solutions of water-soluble polymers, creating a coating just hundreds of nanometres thick. When heated to high temperatures, this layered, 'intumescent' film reacts to form a carbon-based foam that lowers the amount of gas fuelling the burn and slows heat transfer, inhibiting ignition. Flame testing showed that whereas the material burned when coated with just five protective layers (pictured, left panel), 20 layers were sufficient for it to put out the flame soon after ignition (right panel).

Such coatings may provide an alternative to chlorinated or brominated flame-retardant chemicals, which persist in the environment if they leach from fabrics, and show signs of toxicity in animal studies.

Adv. Mater. 10.1002/adma.201101871 (2011)