Given that they're applied to items such as furniture and home insulation, it would really be best if flame-retardant coatings didn't emit toxic fumes. That's why scientists from Texas A and M University have developed a non-toxic alternative, made from natural renewable materials.

The new coating was created by a team led by Dr. Jaime Grunlan, in collaboration with colleagues at Sweden's KTH Royal Institute of Technology.

Applied in multiple layers as a water-based solution, it incorporates cellulose nanofibrils (tiny fibers) obtained from plants' cell walls, along with nanoplatelets (yes, tiny plates) of vermiculite clay. As the solution dries, it transforms into a thin transparent film, in which the fibers and platelets are stacked together to form a brick wall-like structure. This serves as a non-combustible, oxygen-impermeable barrier, minimizing the amount of heat that can reach the material underneath.

In lab tests, the flexible coating was applied to polyurethane foam, of the type that is commonly used for furniture cushions. When that polyurethane was subsequently exposed to the flame of a butane torch, only the surface level of the foam was affected, leaving the rest unscathed. By contrast, when samples of uncoated foam were torched, they immediately melted.

"The nanobrick wall structure of the coating reduces the temperature experienced by the underlying foam, which delays combustion," says Grunlan. "This coating also serves to promote insulating char formation and reduces the release of fumes that feed a fire."

The researchers are now refining the technology, and are investigating methods of producing the coating on a commercial scale.

A paper on the research was recently published in the journal Advanced Materials Interfaces.