"We believe this alternative to flame retardants can prove very useful for removing potential hazards from products that children and adults use every day."Christopher Ellison, University of Texas at Austin
Inspired by a naturally-occurring material found in marine mussels, researchers at the University of Texas at Austin have created a novel, environmentally-friendly flame retardant. Existing flame retardants are often toxic and can accumulate over time in the environment and living animals, including humans.
Flame retardants are added to the polymer foams found in mattresses, sofas, car upholstery and many other consumer products. Once incorporated into the foam, these chemicals can migrate out over time, releasing toxic substances into the air and environment. Throughout the US, there is pressure on state legislatures to ban flame retardants, especially those containing brominated compounds, a mix of human-made chemicals thought to pose a risk to public health.
A team led by Cockrell School of Engineering associate professor Christopher Ellison has now found that a synthetic coating of polydopamine, derived from the neurotransmitter dopamine, makes a highly effective, water-applied flame retardant for polyurethane foam. The researchers believe their dopamine-based nanocoating could be used in lieu of conventional flame retardants. The researchers' findings are published in Chemistry of Materials.
"Since polydopamine is natural and already present in animals, this question of toxicity immediately goes away," Ellison said. "We believe polydopamine could cheaply and easily replace the flame retardants found in many of the products that we use every day, making these products safer for both children and adults."
The UT Austin team found that applying the polydopamine coating to foams led to a 67% reduction in the peak heat release rate, a measure of fire intensity. The polydopamine flame retardant's ability to reduce a fire's intensity was about 20% better than existing flame retardants commonly used today, even though the team applied less polydopamine by weight.
Researchers have already studied the use of synthetic polydopamine for a number of health-related applications, including cancer drug delivery and implantable biomedical devices. However, the UT Austin team is thought to be one of the first to investigate using polydopamine as a flame retardant. To the research team's surprise, they did not have to change the structure of the polydopamine from its natural form to use it as a flame retardant. They were also able to coat the polydopamine onto the interior and exterior surfaces of the polyurethane foam by simply immersing the foam into a water solution of dopamine for several days.
Ellison explained that he and his team were drawn to polydopamine because of its ability to adhere to surfaces, as demonstrated by the fact that marine mussels use the compound to stick to virtually any surface, even non-stick Teflon. Another advantage of polydopamine is that it contains a dihydroxy-ring structure linked with an amine group that can be used to scavenge or remove highly reactive molecules known as free radicals. These are produced during the fire cycle as the polyurethane foam degrades, and their removal is critical to stopping the fire from continuing to spread. In addition, polydopamine produces a protective coating called char, which can block the fire's access to the foam. The synergistic combination of all these processes makes polydopamine an attractive and powerful flame retardant.
Ellison and his team are now testing to see whether they can shorten the coating time or develop a more convenient application process. "We believe this alternative to flame retardants can prove very useful for removing potential hazards from products that children and adults use every day," said Ellison. "We weren't expecting to find a flame retardant in nature, but it was a serendipitous discovery."
This story is adapted from material from the University of Texas at Austin, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.