Fire-retardant coating developed with renewable materials

Scientists have developed a flame-retardant coating using renewable, non-toxic materials readily found in nature, paving the way for more effective fire protection for several widely used materials.

Successful development and implementation of the coating could provide better fire protection to materials including upholstered furniture, textiles and insulation.

"These coatings offer the opportunity to reduce the flammability of the polyurethane foam used in a variety of furniture throughout most people's homes," said Jaime Grunlan, from Texas A&M University in the US.

In nature, both the cellulose -- a component of wood and various sea creatures -- and clay act as mechanical reinforcements for the structures in which they are found.

"The uniqueness in this current study lies in the use of two naturally occurring nanomaterials, clay nanoplatelets and cellulose nanofibrils," said Grunlan, who led the study published in the journal Advanced Materials Interfaces.

"To the best of our knowledge, these ingredients have never been used to make a heat shielding or flame-retardant coating as a multilayer thin film deposited from water," he said.

Among the benefits gained from using this method include the coating's ability to create an excellent oxygen barrier to plastic films -- commonly used for food packaging -- and better fire protection at a lower cost than other, more toxic ingredients traditionally used flame-retardant treatments.

To test the coatings, researchers applied the flexible polyurethane foam -- often used in furniture cushions -- and exposed it to fire using a butane torch to determine the level of protection the compounds provided.

While uncoated polyurethane foam immediately melts when exposed to flame, the foam treated with the researchers' coating prevented the fire from damaging any further than surface level, leaving the foam underneath undamaged.

"The nanobrick wall structure of the coating reduces the temperature experienced by the underlying foam, which delays combustion," Grunlan said.

"This coating also serves to promote insulating char formation and reduces the release of fumes that feed a fire," he said.

The next step for the overall flame-retardant project is to transition the methods into industry for implementation and further development.