The technology in ‘fire paint’ used to protect steel beams in buildings and other structures has found a new life as a first-of-its-kind flame retardant for children's cotton sleepwear, terrycloth bathrobes and other apparel.
According to a report presented at the 242nd National Meeting & Exposition of the American Chemical Society (ACS) in Denver, Colorado, this is the first demonstration of a polymer-based ‘nano intumescent' as flame retardants on clothing.
“People are concerned about the potential toxicity of flame retardants that are currently used on a variety of products, especially children's pyjamas and the foam in children's car seats,” said Jaime C Grunlan, PhD, who led the research at
“The water-based ingredients in this new coating are much less toxic to humans than the so-called ‘halogenated' or ‘brominated' flame retardants used in the past, and they are more environmentally friendly.”
Flame retardants are used on cotton fabrics because they can catch fire easily and burn rapidly with a hot flame. Flame retardants make it more difficult for fabrics to ignite, make them burn slower and make fabrics self-extinguish when the flame is removed – giving time to remove the clothing or put out the flames.
Responding to the need for more environmentally friendly flame retardants, Grunlan's team turned to a technology termed ‘intumescence,’ long used to fireproof exposed interior steel beams in buildings.
At the first lick of a flame, an intumescent coating swells up and expands like beer foam, forming tiny bubbles in a protective barrier that insulates and shields the material below.
Because the ‘nano’ polymer layers are so thin, the liquid seeps deep into cotton fabric and onto each individual cotton fibre, the researchers say.
Existing flame retardants, in contrast, simply settle on fibre bundles like armour and slow the spread of flames, but the fabric still burns and turns black.
When the new nano coating is exposed to a flame, it expands slightly and stops the fire from igniting and burning the fabric — which remains white, except for the small area where the cotton directly touches the flame.
Grunlan's team is in the process of optimising the flame retardant so that it remains on cotton fabrics despite frequent laundering. They also plan to test the coating on other materials, such as polyester and foam, possibly with commercial partners.