Coating Formulation
PTFE coating formulation. This section provides a background to some of the elements involved with the formulations and offers an insight as to why the coatings are so varied both in performance and visual appearance. Formulations of PTFE coatings are created to produce a coating that operates under differing circumstances, as well being able to produce a film that can be sprayed. Manufacturers such as Chemours that produce Teflon® products and Whitford Ltd that produce Xylan® products, continue to formulate and reformulate PTFE coating systems to optimize their functional performance.
Ingredients are selected to offer the required properties to suit different applications. Binders are added to the range of “non-stick” coatings to ensure that the coating adheres to the substrate and pigments give the coating not only colour but the potential for disguising surface irregularities. Additives are included to assist with the spraying of the material, particularly to helping with the flow and the settling of the product onto the substrate to prevent sagging of the wet applied coating.
Take a closer look at the ingredients Binders. These products provide adhesion to the substrate and are particularly important in one-coat systems and in primers. The choice can be restricted because of the cure temperatures of fluoropoloymers and can include:
PAI: PolyAmide Imide PES:
Polyether Sulphone PPS:
PolyPhenylene Sulfide Epoxy
Such binders will, during the curing stage of the coating, allow for the migration of the PFTE to predominantly rise to the top above the binders, thus making way for the attributes of the coating to be at the “contact face”.
Pigments. Various products are included within the formulation and some of them are listed below:
Carbon Blacks
Titanium oxide
Extenders
Chromium oxide
Mica Flakes
Ultramarine Blue
Aluminium Flakes
These products, individually or together can produce a very diverse range of colours. However, it must be stressed that PTFE coatings are not designed as a decorative product, pigments play an important role in tandem with other products to produce the final coating system.
Solvents. Such products are added not only to assist in the “chemical” reaction during cure but also act as a carrier to enable the product to be sprayed in a manner which will produce an even coating. Solvents are either pure solvents or mixed with water, such water-based coatings are becoming more important when meeting environmental issues. Generally, water-based materials are used for coating systems used in Cookware and Industrial applications. Solvent based coating systems are used for Bake-ware, Electrical Appliance and Industrial applications.
Additives. Manufactures add materials to the formulations that will impart particular properties into the coating to produce different attributes. These additives can stabilise the material as well as enhance the flow of the material during the application process. The viscosity can also be changed by additives and most important, additives can play a part in reducing foaming and reduce the settling effect of the product. Another key additive is to eliminate the condition known as “fish eyes” within the applied coating, enabling the coating to wet out.
Fluoropolymer coatings are not pure fluoropolymers. Since fluoropolymers are soft, they do not provide good adhesion alone. Fluoropolymer coatings include binders resins, which act like glue, holding fluoropolymers in place as well as reinforcing them. The most used fluoropolymers resins are PTFE (polytetrafluoroethylene), FEP (fluorinated ethylene propylene) and PFA (perfluoroalkoxy). FEP and PFA are generally used mostly as thick film coatings. PTFE is nor melt processible and is used mostly in granular form as part of the dispersion. PTFE makes the best dry-film lubricant. The amount of PTFE relative to binder resin determines the amount of lubricity of the coating. PTFE does not affect chemical of corrosion resistance.