GAITHERSBURG, US: Gram for gram, novel carbon nanofibre-filled coatings devised by researchers from the National Institute of Standards and Technology (NIST) and Texas A&M University out performed conventional flame retardants used in the polyurethane foam of upholstered furniture and mattresses by at least 160 per cent and perhaps by as much as 1,130 per cent.
The impressive test results, reported in the journal Polymer, suggest that significant fire-safety advantages can be gained by coating polyurethane foam (PUF) with a club-sandwich-like arrangement of thin layers containing carbon nanofibre and polymers. The upshot, said NIST, Researcher, Rick Davis, is that the experimental coating seems to create the equivalent of a “fire-resistant armour” on the porous foam.
Ignition of soft furnishings are responsible for a third of fire-caused deaths of civilians and 11 per cent of property losses due to fires in homes. The flammability of mattresses is regulated by federal law. A complementary rule to regulate the flammability of upholstered furniture has been proposed recently. Several organizations, however, have challenged the health and safety of some flame retardants designed to protect against soft furnishing fires.
Today, recipes for making PUFs result in foams in which fire retardants are embedded in the interior. In contrast, the experimental technology uses the carbon nanofibre fire retardant as a coating that covers all the nooks and crannies on the sponge-like PUF surface. The new approach, said Davis, should be attractive to PUF manufacturers as it does not need major change to foam manufacturing process, saving time and money.
The NIST-Texas A&M team coated square samples of commercially available PUF with four bilayers of a carbon nanofibre-polymer combination. The team used a standard benchtop fire test to measure the fire performance of coated and uncoated PUF. The carbon nanofibre coatings reduced PUF flammability (measured as the peak heat release rate from an ignited specimen) by 40 per cent. That result was more than 3 times better than achieved by putting the same carbon nanofibre in the foam.
When compared at the same concentrations, the carbon nanofibre coating significantly outperforms three classes of commercially available flame retardants commonly used in PUF. Reductions in flammability achieved with the coating, according to the researchers, were 158 per cent better than the reduction calculated for nonhalogens, 288 per cent better than halogens, and 1,138 per cent better than halogen-phosphorous flame retardants.
Additionally, the experimental coating “Prevents the formation of a melt pool of burning foam, which in a real fire scenario, may further reduce the resulting fire threat of burning soft furnishings,” the authors wrote.
(C) National Institute of Standards and Technology News