PFA Non Stick Coating
PFA non stick coating resins, such as Dupont PFA, are relatively newer fluorocarbon resin products. Important for designers and equipment manufacturers to know what separates them from the crowd.
Tensile strength, stiffness, and flexural modulus are outstanding. Both at cryogenic and higher continuous temperatures (500 F). With a lower molecular weight than PTFE, it is not intended for low friction.
The PFA non stick coating is defined by a perfluorocarbon compound. This is a type of fluoropolymer in which the hydrogen directly attached to the carbon atoms is replaced by fluorine. The result is protection from chemical corrosion not unlike fully fluorinated polymers. Chemical resistance is outstanding.
For example, the PFA non stick coating is chemically inert to strong mineral acids, inorganic bases, inorganic oxidizers, or salt solutions. Its resistance to organic compounds includes acids, anhydrides, aromatics, aliphatic hydrocarbons, alcohols, aldehydes, ketones, ethers, esters, chlorocarbons, fluorocarbons, and mixtures of these compounds. Though halogen products containing fluorine, for example, will attack.
So, why the advantage in the PFA non stick coating for corrosion protection? Besides high permeation strength, thickness is key. With the ability to reach 0.010 inch or more, chemical penetration can be significantly retarded, thus reducing the likelihood of reaching the corrosion vulnerable substrate. This is especially important in food processing, where cleaning wash-down may include acids, bases, and oxidizing agents.
What about PFA non-stick coating performance? Besides low surface energy (non wetting) look again to permeation strength. This becomes more evident in applications involving sticky compounds with sublimation byproducts (solids converted to vapors).
Keep in mind higher temperatures increase rates of permeability. It is the fall in specific gravity, the result of more spacing between molecules and more molecular activity, that causes the easier pathway for diffusion-permeation.
The PFA non stick coating is in a class known as melt processable fluoroplastics. This enables the compound to form continuous, monolithic films, with comparatively lower micro porosity.
The PFA non stick coating is similar to PTFE and FEP, although it has somewhat better mechanical properties than FEP at temperatures above 302 degrees Fahrenheit, and can be used operationally to 500 degrees Fahrenheit. It is about equal to PTFE in chemical resistance.