There are indications that more than three thousand years ago some ancient Greeks might have made and used nonstick pans to bake bread. Mycenaean Greek skillets had a cooking side covered with tiny holes that archeologists believed helped to evenly spread oil over the griddle so that dough wouldn't stick while being cooked.
In the modern history of nonstick coating technology, while working at DuPont in 1938 Roy Plunkett accidently invented polytetrafluoroethylene (PTFE). Better known today by its trademarked name Teflon®, PTFE coated nonstick cookware started to hit the selling floors in the early 1960s.
Why PTFE is Used for Nonstick Coatings
PTFE coating's single most important property that makes it so great a choice for nonstick cookware is its very low coefficient of friction (CoF). As a result, most substances (in this case food) won't stick to it and can be easily removed from the cooking surface.
Early PTFE coated cookware suffered from poor quality which often resulted in a short product lifespan. In subsequent years a lot of research and development was conducted to improve the quality and adhesion of today's PTFE coating services. The result is that nonstick cookware, while once considered disposable, now accounts for 75 percent of all cookware and bakeware sold.
The quality of PTFE coatings has come so far that nowadays some manufacturers offer a lifelong guarantee on the coating of their products. PTFE's nonstick characteristic also makes it a very good candidate for a variety of uses and industries outside of the kitchen, including coatings for items such as plain bearings, slide plates, gears, and more. And, a PTFE coating's dielectric properties make it a great choice for insulation in wiring for the aerospace and computer industry.
These applications are just a few of the use cases PTFE nonstick coatings offer. Even as technology continues to evolve and enhance the way we live, PTFE coatings will certainly remain a vital component that enhances and improves our daily lives via the tools and equipment we use.
Nonstick Coating Basics
Getting a great nonstick surface on a particular product isn't as easy as simply spraying it with a coat of polytetrafluoroethylene (PTFE). Though some have called it a miracle material, PTFE coatings (also known as Teflon®) can't work wonders on their own. It requires proper preparation, deliberate application, and careful curing for it to function as intended. Blistering, peeling, or flaking can result from missteps in any or all of three specific areas, including:
- The preparation of the surface onto which the coating is applied
- The thickness of the Teflon®/PTFE coating
- The curing process
Surface Pretreatment for Nonstick Coatings
No matter the type of product being coated, its substrate needs an initial cleaning or treatment to prepare it for the nonstick coating. The nonstick coating applicator may start by roughing the surface by either:
- Blasting it with aluminum oxide
- Etching it with chemicals, or
- Applying a phosphate coating
The practice of blasting, etching, or phosphating the substrate helps the PTFE bond to it and provides for a longer-lasting and more durable final product.
Nonstick Coating Thickness
The way in which a licensed coating applicator applies a Teflon®/PTFE coating to a substrate is also an important factor in the nonstick coating process. Best practices dictate putting on the coating according to a specific dry film thickness (DFT), normally 0.0003-0.0008" per side for a 1 coat system. Yet, an overly generous amount of DFT might result in a flaking or blistered finish, while applying too little may leave the final product with an incomplete layer of Teflon®/PTFE.
The Curing Process for Nonstick Coatings
Though curing comes last in the coating application process, it can cause a disproportionate number of problems if performed incorrectly. PTFE-coated products need to be heated to a temperature between 715° and 750° F to correctly cure. Exactly how long the curing process takes, however, will depend on the nature, size, thickness and material of the coated products. Under curing of the Teflon®/PTFE will result in the coating not being sintered and premature failure.
There are as many potential blemishes that can result from variables in the curing process. Too low of a temperature can cause coatings to peel while heating too quickly can lead to a pebbled appearance. Other issues might include a dull finish and/or a visible fissuring of the nonstick coating.
When the correct steps are followed to apply a nonstick coating you can ensure a more functional final coating with the required properties of Teflon®/PTFE.