The same chemicals that make non-stick cookware perform so well are also some of the most concerning for health and the environment. Per- and polyfluoroalkyl substances (PFAS), often called “forever chemicals,” are highly resistant to breaking down and can build up in the body over time.
Researchers at the University of Toronto may have found a safer alternative. In a study published in Nature Communications, they describe a new coating that repels both water and grease at a level comparable to traditional PFAS-based coatings, but with dramatically reduced amounts of these chemicals.
“The research community has been trying to develop safer alternatives to PFAS for a long time,” said Professor Kevin Golovin, who leads the Durable Repellent Engineered Advanced Materials (DREAM) Laboratory at the University of Toronto. “The challenge is that while it’s easy to create a substance that will repel water, it’s hard to make one that will also repel oil and grease to the same degree. Scientists had hit an upper limit to the performance of these alternative materials.”
The coating uses a silicone-based material known as polydimethylsiloxane, or PDMS, enhanced with very short PFAS molecules that are considered far less harmful than the long-chain versions found in many consumer products. Graduate student Samuel Au developed a new chemistry process for this hybrid material, which the team calls “nanoscale fletching.”
“Unlike typical silicone, we bond short chains of PDMS to a base material — you can think of them like bristles on a brush,” said Au. “To improve their ability to repel oil, we have now added in the shortest possible PFAS molecule, consisting of a single carbon with three fluorines on it. We were able to bond about seven of those to the end of each PDMS bristle.
“If you were able to shrink down to the nanometer scale, it would look a bit like the feathers that you see around the back end of an arrow, where it notches to the bow. That’s called fletching, so this is nanoscale fletching.”
Tests on coated fabric placed the material on par with many conventional PFAS coatings in terms of oil and water resistance, according to a scale used by the American Association of Textile Chemists and Colorists.
“While we did use a PFAS molecule in this process, it is the shortest possible one and therefore does not bioaccumulate,” Golovin said. “What we’ve seen in the literature, and even in the regulations, is that it’s the longest-chain PFAS that are getting banned first, with the shorter ones considered much less harmful. Our hybrid material provides the same performance as what had been achieved with long-chain PFAS, but with greatly reduced risk.”
Golovin said the team is interested in partnering with manufacturers to scale up the process.
“The holy grail of this field would be a substance that outperforms Teflon, but with no PFAS at all,” he said. “We’re not quite there yet, but this is an important step in the right direction.”
The research was supported by the Canada Foundation for Innovation and the Natural Sciences & Engineering Research Council.