Researchers at the University of Toronto are working with a silicone polymer called polydimethylsiloxane (or PDMS) to develop a safer alternative to non-stick coatings, mostly steering away from the PFAS group of chemicals and its related health and environmental impacts.
The technique called nanoscale fletching has led to a repellent material with greatly reduced levels of per- and polyfluoroalkyl substances (PFAS), which are widely used not only in cookware, but also in water-resistant fabrics, food packaging and even cosmetics.
The research team used a PFAS molecule in its process, but notes that it is the shortest possible and would not bioaccumulate.
“If you were able to shrink down to the nanometre 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,” says U of T Department of Mechanical and Industrial Engineering PhD student Samuel Au.
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Au notes that unlike typical silicone, his team bonds short chains of PDMS to a base material.
“You can think of them like bristles on a brush,” says Au in a July statement from U of T. “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.”
PFAS molecules are made of chains of carbon atoms, each of which is bonded to several fluorine atoms. The inertness of carbon-fluorine bonds is responsible for the non-stick properties of PFAS. However, this chemical inertness also causes PFAS to resist the normal processes that would break down other organic molecules over time.
Au and the team coated a piece of fabric with their new material, then placed drops of various oils on it to see how well it could repel them. On a scale developed by the American Association of Textile Chemists and Colorists, the new coating achieved a grade of 6, placing it on par with many standard PFAS-based coatings.
U of T Department of Mechanical and Industrial Engineering Professor Kevin Golovin, who heads the Durable Repellent Engineered Advanced Materials (DREAM) Laboratory at U of T Engineering, says, “The holy grail of this field would be a substance that outperforms Teflon, but with no PFAS at all. We’re not quite there yet, but this is an important step in the right direction.”
The nanoscale fletching technique is described in a paper published in Nature Communications.
