At this very moment, you are likely sitting on a chair made with flame retardant, holding a cellphone doused in flame retardant, or inhabiting a building whose wiring and insulation are infused with flame retardant — perhaps all at once.
The ubiquitous nature of these chemicals is mostly due to a well-intended effort to prevent the start and spread of fire. But scientific studies have raised concerns about common chemicals used as retardants, linking exposure with cancer, lower IQ, delayed mental development, and other problems. Scientists have also found that such chemicals have traveled into our bodies; they’ve been detected in human breast milk and toddler urine.
Now researchers have identified an alternative flame retardant that outperforms existing formulas — a chemical that’s nontoxic, environmentally friendly, and inspired by the sticky mucus of marine mussels.
“Mussels can attach to anything: painted surfaces, metal surfaces, Teflon, you name it,” says Christopher Ellison, a chemical engineer at the University of Texas at Austin who led the study in the October issue of the journal Chemistry of Materials. A flame retardant that did the same, Ellison mused, would not easily flake off a surface or leach into the environment.
His team soaked polyurethane foam — a highly flammable material used in many consumer products — in water mixed with dopamine, a chemical present in our bodies that plays an important role in brain signaling. Then the team reduced the acidity of the liquid, causing the individual molecules of dopamine to link together, forming long chains of dopamine, called polydopamine, within and around the foam.
Polydopamine mimics the adhesive proteins in the mucus of mussels, and similar chemicals are known to subdue highly reactive molecules called free radicals released by heat and fire. The team soaked the foam in the liquid for three days.
Once the foam was dry, they promptly torched it. “My graduate students loved doing those tests,” Ellison says with a laugh. When exposed to flames, the polydopamine coating formed a char on the outside of the foam, similar to the black crust that forms on a marshmallow held too close to the campfire. The char protected the inside of the foam, preventing it from burning, and the flame quickly went out. In comparison, foam with no retardant melted into a flaming, dripping white goop, transferring the fire to underlying materials.
In further tests, polydopamine reduced the amount of heat generated by fire better than several commercial flame retardants, all while using a smaller amount.
Numerous manufacturing companies have already contacted Ellison with questions about the retardant, he says. His team is now testing how well polydopamine works on other fabrics, including nylon, cotton, and polyester.