What sounds like fixings for a wizard’s potion—a dash of clay, a dab of fiber from crab shells, and a dollop of DNA—actually are the ingredients of promising green fire retardants invented by researchers at the National Institute of Standards and Technology (NIST). Applied to polyurethane foam, the bio-based coatings greatly reduced the flammability of the common furniture padding after it was exposed to an open flame. Peak and average rates of heat release—two key indicators of the magnitude of a fire hazard—were reduced by 48 percent and 77 percent, respectively, the NIST team reports in the journal Green Materials.* “This is the biggest reduction in flammability that we have achieved to date,” says team leader Rick Davis. The all-natural coatings outperform other promising experimental fire-retardants that the NIST researchers have devised with their layer-by-layer assembly method.** But Davis says the bio-based coatings must be applied more generously, in stacks of about 20 layers as compared with six or seven layers. Although still under study, the all-natural formulations might offer an alternative to existing fire retardants, including some that have been linked to human health risks and environmental problems. The new coatings use negatively charged DNA molecules to link two positively
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