Who Needs Teflon® Coating, and Why?

Three Prevalent Uses for Fluoropolymer Coating

Precision Coating serves its customers with three prevalent uses for Teflon^® coating. They are lubricity or friction reduction, non-stick or release, and corrosion or chemical resistance. Teflon^® also has properties of high and low temperature withstand, abrasion resistance, electrical resistance, and is hydrophobic. Teflon^® adheres and cures best on metal parts, because the surface can be properly prepared for the addition of coating, and also withstand the curing temperatures. Most plastics will distort or melt at the lowest cure temperatures. So any designer of metal parts that needs low friction, easy release, or corrosion protection, may consider Teflon^® coating. We will use the terms Teflon^® and PTFE (polytetrafluoroethylene) interchangeably, but Teflon^® is DuPont’s trade name for PTFE. Other companies also make PTFE, but DuPont was first, so many people are familiar with the word Teflon^®. PTFEs, in turn, belong to a larger family of coating formulae, called fluoropolymers.

Medical Applications

Medical guidewires need to have PTFE coating so that they slide easily inside veins, and then when those wires reach their intended destination, catheters or tubes slide easily over the wire. Procedures can then be accomplished through the tube. The PTFE makes the wire slide easily when small adjustments are being made to steer the wire, and also back it up, if it’s not going the right way.

The field of orthodontics uses PTFE on wires and fittings, mainly for the cosmetic benefit, with white as the color of choice. PTFE is chosen because it is chemically inert and thus benign for the patient.

Also, in the medical arena, it is common to use coated wire as a mandrel, over which catheters and other devices can me molded to exact diameters. For those applications, the PTFE must provide optimum release of the molded resin, repeated use, smooth surface profile, and sometimes high temperature. A common win-win is that a mandrel will often require a non-coated end, so that it can be held (cured PTFE is hard to hold), and the coater will want an end to hold, to facilitate the coating process.

Highly Engineered Components, or Industrial Applications

Applications requiring similar mold release benefits, but not in wire form, are generally called “industrial,” and that is probably where the greatest variation of coating types are specified. Processing temperature becomes a top criterion, followed closely by resistance to wear, and release properties. The mold cavities are typically aluminum, and are coated with PTFE and other fluoropolymers in combination, with a top service temperature of 500° Fahrenheit. As with anything else that must resist high temperature—the higher it is, and longer the duration—the shorter the lifespan of the coating’s good properties will be. Some coatings will claim higher service temperatures, even to 600°F, and you may trust that there is data to back it up, but remember that no coating is forever. A great benefit of the spray and cure method of applying coatings is that build-up is only about .001”, so mold designers usually can neglect the coating’s impact on size of their finished parts.

A sub-group of mold applications is what we call heat-sealing, which is where a plastic is melted only very locally, and for short duration. These parts look a lot like shallow molds, and the coating must withstand both high temperature and wear. The Silverstone^® formula is a very popular choice.

Non-stick properties are also required for process components of glues, resins, or foods while they are in liquid state. The main objective is that these parts can be cleaned and re-used or refilled, without aggressive or labor-intensive cleaning. Temperatures are often low enough to use the very optimum formula for non-stick, often referred to as Teflon^® S and FEP (fluorinated ethylene propylene).

Fluoropolymers for low friction are used on parts that bear significant load, but the fluoropolymer must be carefully matched to satisfy conditions of pressure, cycles, temperature, assembly variation and external contamination. These coatings are often in the dry-film lubricant category, and anti-wear is typically as important as anti-friction.

Corrosion resistance is possibly the least common use for fluoropolymers, and there is a wide spectrum of success and failure, depending on many variables of coating integrity, thickness, service temperature, pressure, solution concentration, and handling. There are also plenty of other economical ways to protect parts from corrosion. That said, PFA (perfluoroalkoxy) formulae are non-porous, and can do a great job protecting parts. Other fluoropolymers are hydrophobic, and therefore offer good protection, even though there are microscopic pores in some formulae. For maximum protection, a thicker build can be achieved with electrostatic powder coating, and when part details are a priority, a spray on, and cured method provides thin coverage, conforming to all contours.

These are the main uses for the coatings we apply at Precision Coating, but are not the only ones. We often advise customers on completely new ideas for coating their parts. We welcome your inquiries for fluoropolymer coating, and look forward to talking with you. Please contact us about your fluoropolymer coating needs.