Engineers have developed a new non-stick coating that could finally compete with Teflon without the dangerous "forever chemicals" that have prompted health alarms. By combining silicone-based bristles with the smallest possible PFAS molecules, the research team created a surface that resists water and oil as effectively as traditional coatings.
Researchers at the University of Toronto's School of Applied Science and Engineering have created a new material that could provide a safer alternative to non-stick coatings widely used on cookware and other everyday items.
This innovative product repels water and oil as effectively as many standard non-stick surfaces, but with much lower levels of per- and polyfluoroalkyl substances (PFAS). PFAS are a class of chemicals associated with environmental and health concerns.
“The research community has long been working to develop safer alternatives to PFAS,” said Professor Kevin Golovin (MIE), director of the Durable Waterproof Engineering Advanced Materials (DREAM) Laboratory in the Faculty of Engineering at the University of Toronto.
"The challenge is that while it's easy to make a substance that repels water, it's harder to make one that repels oil and grease to the same degree. Scientists have reached the upper limit of the performance of these alternative materials."
Teflon (polytetrafluoroethylene, or PTFE) was first introduced in the late 1930s and is known for its excellent resistance to water, oil, and grease. Teflon belongs to the PFAS family.
PFAS molecules are made of carbon atoms bonded to multiple fluorine atoms. These carbon-fluorine bonds are extremely stable, and it’s this stability that gives PFAS its powerful non-stick properties.
The same chemical stability also makes PFAS resistant to natural decomposition processes. This persistence in the environment has earned it the nickname "forever chemical." In addition to their persistence, PFAS accumulate in biological tissues and their concentrations increase as they move up the food chain.
Multiple studies have linked exposure to high levels of PFAS to certain types of cancer, birth defects and other health problems, and long-chain PFAS are generally considered more harmful than shorter-chain PFAS.
Despite the risks, PFAS remain ubiquitous in consumer products due to a lack of alternatives: not only are they widely used in cookware, but also in rainproof fabrics, food packaging, and even cosmetics.
“The material we’ve been working on to replace PFAS is called polydimethylsiloxane, or PDMS,” Golovin said.
PDMS is often sold as silicone, and depending on its formulation, it can be extremely biocompatible—in fact, it is often used in devices implanted in the body. But so far, we haven’t been able to get PDMS to perform at the level of PFAS.
To solve this problem, MIE doctoral student Samuel Au developed a new chemical technique that the team calls nanoscale fletching. The technique was published in the journal Nature Communications.
“Unlike typical silicone, we bond short chains of PDMS to the substrate—you can think of them like bristles on a brush,” Au said.
To improve their ability to repel oil, we now add the shortest PFAS molecule, which consists of one carbon atom and three fluorine atoms. We were able to bond approximately seven of these molecules to the end of each PDMS bristle.
"If you could shrink it down to the nanoscale, it would look a bit like the feathers around the nock, which is the notch in the bow. That's called fletching, so it's nanoscale fletching."
Au and team applied their new material to a piece of fabric and then dropped various oils on it to see how well it repels the oil. The new coating reaches Level 6 according to the oil-repellent rating standards set by the American Society of Textile Chemists and Colorists, which is comparable to many standard PFAS-based coatings.
"While we do use a PFAS molecule in this process, it is the shortest molecule and therefore does not accumulate in organisms," Golovin said.
"What we see in the literature, and even regulations, is that the first to be banned are long-chain PFAS, while short-chain PFAS are considered to be much less harmful. Our hybrid material performs the same as long-chain PFAS, but with significantly less risk."
Golovin said the team is open to working with nonstick coating manufacturers interested in scaling up and commercializing their products. In the meantime, they will continue to research more alternatives.
“The ultimate goal in this field is a substance that performs better than Teflon but is completely PFAS-free,” Golovin said.
"We're not quite there yet, but it's an important step in the right direction."
Compiled from /scitechdaily