College Station, Texas -- A thin nano-polymer coating developed by materials engineers at Texas A&M University could keep cotton clothing and polyurethane-foam-based furniture from going up in flames.
The intumescent coating, developed by a team led by Dr Jaime Grunlan, an associate professor in the Department of Mechanical Engineering, is also claimed to be environmentally friendly.
Grunlan works with polymer nanocomposites that have properties similar to those of metals and ceramics -- conducting electricity, for instance, while maintaining the properties of polymers, such as low density.
And he now claims: "We can now make cotton fabric that doesn't burn at all."
The technology involves coating all the microscopic fibres in a fabric with a thin composite -- about one-tenth of a micron thick -- of two polymers that intumesce, producing a protective coating of carbon foam when exposed to high temperatures.
The films are assembled layer-by-layer by depositing the coating onto the surface of the fibre.
Grunlan says the technology will be suitable for all types of clothing, but it could also be used in foams, such as those found in sofas, mattresses, theatre and auditorium seats, airplane seat cushions, and building insulation.
On polyurethane foam, a coating of chitosan (a natural material extracted from shrimp and lobster shells) and clay is deposited to eliminate melt dripping during burning.
The nanocomposite mixture coats the interior walls of foam. The result is that when burned, the treated foam keeps its shape instead of puddling at high temperatures like untreated polyurethane foam does. This quality eliminates the "melt-dripping" effect that further spreads fires.
"It's like we're building a nano-brick wall within each cell of the foam," Grunlan says.
Similar work, using carbon nano-fibres as an intumescent coating for flexible foam, has been carried out at the US National Institute of Standards and Technology - NIST (see UTI Dec/Jan 2011, p12).