College Station, Texas – Scientists from Jaime Grunlan’s lab at Texas A&M University have developed a fire-retardant coating. Although it was developed to protect wood, they suggest that it could also be applicable to polyurethane products, including PU foam and 3D-printed components.
In contrast to most current fire-retardant treatments, Grunlan said, its ingredients are environmentally benign. It builds on polyelectrolyte coating technology first invented in Grunlan’s lab more than a decade ago. This relies on first dipping a fabric in a polymer bearing a lot of positive charges, and then in another with a lot of negative charges. These steps are repeated until the coating is sufficiently thick, with the charges drawing the layers together into ionic bonds, giving a coating that can extinguish a flame.
However, this process is not applicable to non-fabric substrates such as wood, as they take too long to absorb the polymers. The new process involves dipping the substrate in a mixture of the positively charged polymer polyethyleneimine (PEI), the monomer hydroxyethyl methacrylate phosphate (HMP), and a photoinitiator. When exposed to UV light, the photoinitiator turns the HMP into a negatively charged polymer. This forms a covalently bonded polyelectrolyte complex with the PEI, giving a transparent coating a few micrometres thick.
In lab flame tests, it reduced the amount of heat released during burning, and rapidly formed a protective surface layer of char. Smoke production was reduced by more than half.
As well as dipping, the coating could be applied by spraying or pressure treatment. ‘The coating could reduce flame spread and smoke production, which could limit damage and give people more time to evacuate,’ said Thomas Kolibaba, the researcher who developed the coating.
The work was presented at the American Chemical Society’s spring 2022 meeting, held online and in San Diego. A video about the research is at www.acs.org/firecoating.