NEWS OF THE WEEK
NANOMATERIALS: Ultrathin films could
replace troublesome flame retardants
A
30-NM-THICK POLYMER coating can prevent
the spread of flames on foam used in home furnishings (ACS Macro Lett., DOI: 10.1021/ mz400105e). The coating, which consists of a sulfurbased polymer and a carbohydrate polymer found in crustacean shells, could be an environmentally friendly alternative to the flame retardants used today in furniture foam, its developers say. Furniture cushions are typically made of highly flammable polyurethane foam. To meet fire safety guidelines, manufacturers treat the foam with flameretardant chemicals. Toxicologists and environmental scientists worry about these brominated chemicals because studies have shown that some can act as endocrine disrupters or lead to neurological problems. The European Union has banned several of the compounds, and regulatory agencies in the U.S. and Canada have started to scrutinize the chemicals’ use. Jaime C. Grunlan, a mechanical engineer at Texas A&M University, wanted to find flame-retardant formulations that do not affect the foam’s stiffness and are less toxic than current compounds. The coating he and his team developed consists of polyvinylsulfonic acid (PVS) and chitosan, a long carbohydrate molecule derived from the shells of shrimp and other crustaceans. To produce the coating, the researchers dip foam
in water solutions of the two polymers. Chitosan is positively charged in water, whereas PVS is negatively charged. The oppositely charged polymers attract each other and become entangled, creating the coating. The 30-nm-thick film increases the weight of the foam by just 5.5% and doesn’t alter the foam’s stiffness. The researchers tested the coating by exposing treated foam to a flame from a butane torch for 10 seconds. Whereas uncoated foam burned up completely, the fire on the coated foam went out once the researchers turned off the torch. It would take more than three times as much conventional flame-retardant material by weight to achieve the same effect, Grunlan says. He explains that when PVS burns it gives off vapors of sulfur oxides, which are nonflammable. “This creates a gas blanket on the foam surface, cutting off oxygen and starving the fire,” he says. Fireproof nanocoatings are cutting-edge technologies in the field, says Rick D. Davis, who works on clay-based nanocoatings in the flammability reduction group at the National Institute of Standards & Technology. Grunlan’s nanocoating is novel because it’s the first to use sulfur-based gas to extinguish fire, Davis says. Both the clay-based and polymer nanocoatings, he says, are more effective and could be less toxic than commercially available flame retardants.—PRACHI PATEL, special to C&EN
Researchers expose a piece of polyurethane foam to an open flame from a butane torch for 10 seconds. A polymer nanocoating keeps the fire from spreading once the torch is off.
JAIME GRUNLAN/TEXAS A&M
COATINGS FIGHT FURNITURE FIRES
SHUTTERSTOCK
REGULATION Europe bans three neonicotinoids linked to honeybee population declines The European Commission (EC) plans to move ahead with a two-year ban on three neonicotinoid pesticides. The move came after member states failed to reach a majority for or against the ban during an appeals committee vote on April 29. The restrictions will go into effect in December. The decision to ban the three chemicals—clothianidin, imidacloprid, and thiamethoxam—was prompted by a study by the European Food Safety Authority that associated the pesticides with numerous risks to honeybee health. Fifteen member states supported the restriction, eight voted against it, and four
abstained during the appeals committee vote. Because a qualified majority was not met, the decision was handed over to the EC—the administrative arm of the European Union—which chose to go forward with the ban. “I pledge to do my utmost to ensure that our bees, which are so vital to our ecosystem and contribute over €22 billion [$29 billion] annually to European agriculture, are protected,” Tonio Borg, European commissioner for health and consumer policy, said in a statement after the vote. The commission will release its plan for removing the three pesticides from the European marketplace in coming weeks. Bayer CropScience, maker of clothian-
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MAY 6, 2013
idin and imidacloprid, called the decision “a setback for technology, innovation, and sustainability.” The company claims that the restrictions will lead to reduced crop yields, lower food quality, and less competitive European agriculture. Bayer remains convinced that neonicotinoids are safe for bees, when used according to label instructions. “Clear scientific evidence has taken a backseat in the decision-making process,” the company says. The environmental group Friends of the Earth hailed the EC’s decision, calling it “a significant victory for bees and common sense.” But the group warned that bees face many threats beyond pesticides.—BRITT ERICKSON
