Why doesn’t anything stick to Teflon? - Ashwini Bharathula
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If you would like to see how non-stick cookware is made industrially, here is Discovery and Science Channel's ‘How It's Made - Non-Stick Cookware’ episode. Take a look to learn more about this amazing material.
Non-stick cookware is just one of many applications that Teflon has served over years. PTFE can be fabricated in many forms, such as pastes, tubes, strands and sheets. In the following article, you can see how a PTFE-fiberglass fabric originally used for Apollo spacesuits has gone on to become a unique component of architecture around the world.
When stretched, PTFE forms a strong porous material called expanded PTFE (ePTFE). A commercial name for this form of Teflon in Gore-Tex®, which is marketed as a waterproof, breathable fabric. You can read more about Teflon’s major applications at this link.
We know that nothing sticks to Teflon because Teflon is unable to form chemical bonds with outside molecules. Even the weaker short-range interactions like van der Waals forces with other molecules are ineffective. You can get some ideas in the article: If nothing sticks to Teflon, how does it stick to pans? about what are some of the strategies used to get PTFE to stick to a pan.
Let’s talk about Teflon’s slipperiness. How are other materials able to slide on it so easily? PTFE’s extreme slipperiness can be attributed to its super low coefficient of friction. Watch the following demonstration: How Does PTFE Make Things Slippery? from the Science channel that shows how PTFE can be used to reduce friction.
The source here lists the coefficient of friction for Teflon-on-Teflon to be an order of magnitude lower than that of steel-on-steel scenario. Teflon is unique in that it not only has a super low coefficient of friction, it's also very soft because of which wear is an issue. Here’s a study that talks about the wear mechanisms in PTFE in detail
Here’s a quick summary of what happens when a material like steel slides on a surface coated with PTFE. At the start of sliding, the surface of the PTFE fractures and lumps are transferred to its mating surface. As sliding continues, the lumps spread out to form a thin film. At the same time, the PTFE surface is flattened into an organized layer. Now the two surfaces in contact, both coated with films of PTFE molecules, slide over each other with ease thanks to fluorine’s electronegativity. Now you may be wondering if this mechanism applies to PTFE’s interaction with soft materials like food sliding on your non-stick kitchen pans. Although there are no known concrete studies on exact wear rates of PTFE with soft counter-surfaces like food, it is suspected that this mechanism may still be at play, albeit to a lesser extent. This could be why after prolonged use, you see a discolored patch on the pan, suggestive of slow wear of the PTFE coating.
There are some useful articles relating to safety of Teflon products and PFOA. Following strong regulations from US Environmental Protection Agency, eight major leading companies in the per- and polyfluoroalkyl substances (PFASs) industry are believed to have eliminated PFOA from emissions and products by 2015. A link from the American Cancer Society is provided here. Finally, take a look at his article: Ask a Toxicologist: Is it safe to use Teflon pans?
If you want to know more about the backstory of the lawsuits filed against DuPont and its spin-off company, Chemours, you can read this article: The Lawyer Who Became DuPont’s Worst Nightmare.
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