Exploring the World of Fluoropolymers
A look at processing and coloring these high-performance materials
Fluoropolymers are a family of exceptional, high-performance materials that are widely used today – and for good reason, since they are stable plastics that resist degradation under harsh conditions and are inherently flame retardant. These natural properties make the use of fluoropolymers in industries such as wire and cable, architectural films, transportation, industrial and even medical an excellent choice for many applications.
A Bit of History
It began in 1938, when a DuPont scientist named Dr. Roy Plunkett accidentally created polytetrafluoroethylene (PTFE). The material was found to be very slippery, resistant to high heat, and chemically inert. DuPont, which trademarked this material as Teflon® in 1945, first used the product in military applications and then in nonstick coatings for consumer cook and bakeware1.
Today, fluoropolymers serve a broad range of applications with their unique material properties, including chemical inertness, low friction, weatherability, natural flame retardance, temperature resistance, and barrier properties. These fluoropolymer properties are widely depended on in many different industries. For example, fluoropolymers are used as coatings for wire and cable found in buildings and aircraft thanks to their natural flame retardance. Fluoropolymers are also enabling new technologies: they are used as films that function as a lightweight alternative to glass in solar panels, and to make safe batteries for electric vehicles. Adding to their versatility, formulations can be designed using colors and specialty additives to meet specific needs.
Processing Particulars
Most fluoropolymers, other than PTFE and polyvinyl fluoride (PVF), can be melt processed using conventional thermoplastic extrusion or molding techniques. PTFE can be applied as a coating, extruded as a paste, or molded using compression molding or metal powder-processing techniques. PVF is dispersed in a solvent for melt extruding2.
Fluoropolymers have high melting points and corresponding high processing temperatures and continuous use temperatures, depending on the specific product. Perfluoroalkoxy (PFA), for example, is at the high end; it has a typical continuous use temperature of 500°F (260°C) and typically reaches 715°F (380°C) during processing; equipment temperatures can be even higher than the melt temperature3. At the lower end, polyvinylidene fluoride (PVdF) has a typical continuous use temperature of 300°F (150°C) and typically reaches 450°F (232°C) during processing3.
Precautions should be observed when processing fluoropolymers, which can generate toxic fumes at or above their processing temperatures. Engineering controls, such as local exhaust ventilation, may be required during processing. In some cases, residual gases may slowly evolve from resins or from finished products, so storage spaces may need to be ventilated. When melt processing fluoropolymers, accelerated thermal decomposition should be avoided by having accurate temperature control, and in some cases, using corrosion-resistant materials for processing equipment3. Various types of processing, such as foaming, can have other hazards, and processing recommendations should be carefully followed.
Coloring Fluoropolymers
As mentioned earlier, fluoropolymers can be used in many different areas, and the optimal fluoropolymer type and appropriate color masterbatch will depend on the part’s requirements. For example, the heat and chemical resistance of a fluoropolymer will greatly influence the pigment selection process.
Additionally, each manufacturing process has unique attributes in terms of the speed of the process and demands placed on the material during processing. The high-speed manufacture of thin-wall wire jacketing would require a distinctly different formulation compared to the extrusion of a large cross-section stock shape such as a rod. For wire jacketing, a color masterbatch must be formulated to ensure it can be rapidly mixed and evenly dispersed in a very short time, while also providing sufficient pigment coverage. In contrast, rod extrusion would require very stable pigments due to the longer residence time in the extruder.
Understanding the part size and wall thickness allows a masterbatch to be designed with the appropriate pigment strength, particle size, and dispersibility. Correct selection of these parameters is needed to achieve uniform and repeatable product coloring performance. A thinner wall part must use a smaller particle size and a formulation with good dispersibility to minimize the tendency for pigment particles to form lumps on a part’s surface. Color concentration and viscosity of the carrier can be fine-tuned to maximize dispersion and color consistency.
Fluoropolymers can use a wide range of colors that can be matched to a standard reference color (for example, RAL or Pantone®) or custom matched to a manufactured part. Color masterbatch formulations can produce opaque colors or can be developed with the appropriate pigment particle size and loading to enable translucent colors. Some applications require the use of heavy metal-free colorants. For parts needing added distinction, special colorants allow laser marking of fluoropolymers, or specialized inks can be used for striping and printing.
Ready to Learn More?
Selecting the right fluoropolymer for your application can have multiple nuances, from properties and processing to design and appearance. Learn more about fluoropolymer colorants and solutions tailored for your specific needs.
1SPI, “History of Fluoropolymers” https://www.fluorotec.com/news/blog/the-history-of-ptfe/
2 Sina Ebnesajjad, “Introduction to Fluoropolymers,” Applied Plastics Engineering Handbook (Elsevier, 2011) pp 49-60.
3 The Fluoropolymers Division of the Society of the Plastics Industry, Guide to the Safe Handling of Fluoropolymer Resins–Fourth Edition (2005).