How to Select the Appropriate Formulation for Your Application
Polytetrafluoroethylene (PTFE) is a popular coating material used in various industries for its non-stick and heat-resistant properties. There are two types of PTFE coatings: aqueous-based and solvent-based. Here, we are discussing the difference between the two formulations.
Aqueous-Based and Solvent-Based PTFE Applications
Aqueous-based PTFE coatings are water-based and are known for their environmental friendliness. They are also known for their low volatile organic compound (VOC) content, making them a safer and more environmentally friendly option. Aqueous-based PTFE coatings are also easy to apply and can be used on a variety of substrates, including aluminum, steel, and plastics. Common lifestyle applications you will find them on are cookware, bakeware, and other food-related items, since a thin coating is required. This also makes aqueous-based PTFE coatings perfect for medical devices.
Solvent-based PTFE coatings, on the other hand, are made from solvents such as xylene, toluene, and other volatile organic compounds. They are known for their high-performance properties and are often used in industrial applications that require a thicker coating. Solvent-based PTFE coatings are also more durable and resistant to wear and tear than aqueous-based coatings. In difficult and tortuous path medical applications, a solvent coating is a good choice for use, given the strong adhesive functional requirements. Other common uses are found in the automotive, aerospace, and electronics industries.
All PTFE (polytetrafluoroethylene) is made with a free radical polymerization process combining carbon and fluorine atoms. The resulting polymers are high molecular weight, long straight chain molecules. These polymers exhibit excellent low-friction properties, as well as release, heat resistance, and chemical resistance characteristics.
In aqueous-based formulations, the PTFE active ingredient goes directly from the original polymerization process into the final coating dispersion. Then chromic acid, pigments, and surfactants are added, which help promote substrate adhesion during the high-temperature cure cycles between 700oF and 750oF.
Solvent-based PTFE coatings use a dry, fully cured, ground powder PTFE. This micro-powder is added to an organic solvent containing a binder and pigments. Since the PTFE is already fully cured, only the final cure of the binder has to be reached to promote maximum adhesion. This is typically hundreds of degrees lower than the aqueous dispersions, and it helps decrease oxidation of exposed metals. The lower cure temperature for solvent-based coatings is a perfect fit for nitinol applications in the medical device industry.
Performance and Appearance
Application methods for aqueous and solvent coatings are very versatile and can be deposited using either a spray, dip, or brush.
- The surface finish of aqueous-based coatings is very smooth regardless of the deposition method
- Deposition thicknesses are extremely thin given the particle size of the dispersion that is measured is in the sub-micron range
- Excellent low friction and release
- Target applications—mandrels and tight-tolerance guide wires and core wires
- The surface finish of solvent-based coatings is less smooth, and under high magnification resembles the surface of an orange
- Deposition thicknesses are not as thin as aqueous-based coatings given that the particle size of the PTFE micro powder in the solvent chemistry is measured in the 4- to 7-micron range
- Good low friction and release
- Target applications—guide wires and core wires and low-cure metals, such as nitinol
Precision Coating provides both aqueous-based PTFE dispersions and solvent-based medical-grade PTFE coating chemistries for medical devices. We’d be happy to talk with you about which of these two coatings is the right choice for your next job. Contact us so we can discuss how we can provide you with the best solution. Additional information about Precision Coating is available at www.precisioncoating.com.
This blog post was updated on June 27, 2023. It was originally published on September 28, 2015. To view the original post, click here.