What Is Teflon Coating?
Teflon™ (hereinafter referred to as “Teflon”) coating is a type of surface treatment for materials and is a surface treatment method of coating using Teflon, a fluoroplastic.
This “Teflon™” is a trademarked product by the former DuPont, now Chemours Corporation of the United States. Therefore, only processing manufacturers authorized and licensed by Chemours can use the “Teflon™” brand and name.
Uses of Teflon Coatings
Teflon coatings are used in a variety of fields, including:
- Familiar household products
- Aerospace equipment
- Automotive components
- Coating of electric wires
Teflon coatings are particularly suitable for surface treatment of seals, brake pads, and bearings in automobile transmissions, which are subject to high temperatures due to heat from the engine.
Principles and Characteristics of Teflon Coatings
1. Principle of Teflon Coatings
Teflon coating technology uses a fluorinated resin called Teflon. Teflon has excellent heat and solvent resistance and is electrically non-polar. Therefore, the coating film of Teflon coatings reflects the characteristics of Teflon.
Fluoropolymers other than Teflon are also manufactured by various companies, and coatings using these resins are also conventionally referred to as Teflon coatings.
What is Teflon?
Teflon is a thermoplastic polymer composed of fluorine elements and carbon chains that can be softened and molded by heat. The fluorine in Teflon is stably bonded to the carbon chain, and the excellent chemical, electrical, thermal, and mechanical properties of Teflon are attributed to this molecular structure.
There are nine types of Teflon, including PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane polymer), and FEP (perfluoroethylene propane copolymer).
2. Properties of Teflon Coatings
Teflon has excellent heat and solvent resistance and is electrically nonpolar. The properties of Teflon coatings films reflect these characteristics.
1. Heat Resistance
Teflon coatings have high heat resistance and are not easily deformed by temperature changes. This is because Teflon has a structure in which fluorine and carbon chains are stably bonded, and its properties do not change up to a certain temperature.
For this reason, Teflon is used for surface treatment of automotive components that require heat resistance to withstand the high temperatures generated by engines and resistance to deformation due to temperature changes.
However, at temperatures above 327°C (620.6°F), the melting point of Teflon, the coating becomes a gel, and the mechanical properties of the coated film rapidly deteriorate.
2. Solvent Resistance
Teflon coatings have high solvent resistance. This is because Teflon has extremely high stability against acids, alkalis, and organic solvents.
3. Electrical Properties
Teflon coatings are electrically nonpolar. This is because Teflon has no electrical polarity due to the symmetry of its molecular structure. Parameters such as dielectric constant and power factor of Teflon are constant and unaffected by temperature and frequency, and the insulation resistance is extremely high.
For this reason, Teflon coatings are often used to sheath wires used in the electrical systems of personal computers, robots, and aircraft.
Other Information on Teflon Coatings
1. General Process of Teflon Coatings
There are various methods and processes for Teflon coatings, depending on the type of Teflon, the base material or base metal to be coated, and the purpose of use. The general processes are as follows.
- Preliminary diagnosis
Inspect the base material to be coated for scratches, dents, welding points, etc. that may cause problems. - Degreasing and air baking
After degreasing to remove oil and adhering matter, the coating is air baked at a high temperature (about 300°C or 572°F). At this time, care should be taken if heat distortion is a problem. - Roughening
To remove stains and oxide film from the base metal, blast the surface with alumina abrasive. - Primer (primer coat)
An adhesive is applied to bond the base metal to the Teflon coatings. Primer is not necessary for self-adhesive fluoropolymer coatings. - Drying
Drying is performed at about 100℃ (212°F). Depending on the primer, high-temperature baking at 200°C (392°F) or higher may be required.
Depending on the type of Teflon coatings, a middle coat may be required before the top coat in the subsequent process. - Top Coat (Top Coating)
Teflon coatings agent is applied using a spray gun, powder coating, or other prescribed method. - Baking
The Teflon coatings agent is baked at a specified temperature and time to harden it. - Inspection
Teflon coatings film is inspected for appearance, thickness, pinholes, etc.
2. Thickness of the Teflon Coatings
The thickness of the Teflon coatings film produced through the process described above varies depending on the intended use. Generally, the coating thickness is 20 to 50㎛ for non-adhesive purposes such as mold release improvement, and 300㎛ to 2mm for corrosion resistance purposes such as maintaining the functional appearance of molds.
Very special coatings can be produced with a very thin film thickness of as little as 1㎛. Pinholes in the coating film are an extremely important issue in Teflon coatings. For this reason, thicker coatings are sometimes used to prevent pinholes. For example, coatings thicker than 250㎛ is called “lining”.