1. What are Fluoropolymers?
Fluoropolymers are a class of polymers with a carbon-carbon backbone in which the fluorines are linked by strong fluorocarbon bonds. Its extraordinary strength lies in its resistance to high and low temperatures, severely corrosive environments and most chemicals. These are polymer fluorine atoms that completely or partially replace hydrogen atoms in hydrocarbon polymers .
Fluoropolymers (composed of fluorine and carbon) are also known as perfluoro polymers to distinguish them from fluoroelastomers and partially fluorinated polymers. Different fluorocarbon products may have different molecular weights, which also affect their melting points
2. Features of Fluoropolymers
Characteristics of common fluoropolymers include:
● Resistance to alkali, metals, acids
● low coefficient of friction
● Wear resistance
● Resist extreme weather
● Dielectric (electrical insulation) characteristics are basically independent of power frequency and temperature
● Low temperature resistance
● High temperature resistance
● Moisture resistance
3. Chemistry of Fluoropolymers
The characteristics of fluoropolymers are mainly due to the atomic structure of carbon and fluorine and the covalent bonds in their unique chemical structure. The atomic size of fluorine helps it form a unique protective layer around the bonds between carbon atoms, protecting the backbone of the carbon-carbon bond from corrosive chemical attack and providing stable chemical resistance.
Most fluoropolymer applications require the ability to withstand specific operating environments, for which manufacturers have developed custom engineered products, as well as innovative modifications of neat fluoropolymers.
Some common fluoropolymers include:
4. Fluoropolymers Selection Guide
PFA (Perfluoroalkoxy) is a melt-processable fluoropolymer that combines many of the best traits of PTFE and FEP. At 260 °C, PFA has a higher service temperature than FEP and maintains its mechanical integrity in extreme temperatures even when exposed to caustic chemicals. PFA is a top choice in semiconductor, chemical, oil and gas, aerospace, automotive, pharmaceutical, and medical industries. This fluoropolymer has excellent lubricity, clarity, flexibility, and chemical resistance, making it a versatile choice. See the below table, and select the best suitable Perfluoroalkoxy for your parts.
5. What is PFA?
Common PFA material is a clear granule. PFA is short for perfluoroalkyl, better known as DuPont's brand name, Teflon. Because of the low friction coefficient, PFA has excellent viscous energy. It is a fairly flexible polymer with high stress cracking resistance and resistance to almost all solvents and chemicals. PFA can also withstand high and low temperature conditions. It is capable of providing continuous service temperatures up to 260°C. Offers exceptional flame resistance, chemical stability and high dielectric strength. A wide variety of applications including critical, highly corrosive processes are used in pipelines.
Teflon is one of the most important inventions of the 20th century and has many practical and technical applications in our modern world. We know that there is more than one form, such as PFA and PTFE: Polytetrafluoroethylene (PTFE) and tetrafluoroethylene and perfluoroalkyl vinyl ether (PFA) are two fluoroplastics that are widely used worldwide, their properties are very similar, PFA is also known as "meltable polytetrafluoroethylene".
6. What is PTFE?
Common PTFE material is a white powder. Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. It is one of the most well-known and widely applied PFA. The commonly known brand name of PTFE-based composition is Teflon, a spin-off from DuPont, which originally discovered the compound in 1938.
Polytetrafluoroethylene is a fluorocarbon solid, as it is a high-molecular-weight polymer consisting wholly of carbon and fluorine. PTFE is hydrophobic: neither water nor water-containing substances wet PTFE, as fluorocarbons exhibit only small London dispersion forces due to the low electric polarizability of fluorine. PTFE has one of the lowest coefficients of friction of any solid.
Polytetrafluoroethylene is used as a non-stick coating for pans and other cookware. It is non-reactive, partly because of the strength of carbon-fluorine bonds, so it is often used in containers and pipework for reactive and corrosive chemicals. When used as a lubricant, PTFE reduces the friction, wear, and energy consumption of machinery. It is used as a graft material in surgery and as a coating on catheters.
7. What are the similarities and differences between PTFE and PFA?
1）Molecular structure comparison
PTFE is polymerized from the monomer tetrafluoroethylene, first discovered by DuPont in 1938, and the most widely known brand of PTFE is Teflon®. The figure below shows the structural formula of PTFE, and the yellow balls represent fluorine atoms.
PFA adds a perfluoroalkoxy group, which is equivalent to replacing one fluorine atom in PTFE with a perfluoroalkoxy group. Like PTFE, the formulation of PFA was first invented by DuPont, and the most famous PFA formulation is Teflon PFA. Molecularly speaking, the carbon chain of PFA is relatively short, and the degree of chain entanglement is higher. The figure below shows the structural formula of PFA.
2）Performance comparison
A) In general, the properties of PFA are very similar to PTFE. The maximum continuous use temperature is 260°C, and the minimum service temperature is -196°C) can also be bent and so on.
B) The biggest difference between them is that PFA is melt processable, while PTFE can’t. This means that PFA can be processed with conventional injection molding and screw extrusion techniques. PFA has a higher service temperature than FEP and maintains its mechanical integrity in extreme temperatures even when exposed to caustic chemicals.
C) PTFE hydrolysis resistance, so it is not easily affected by moisture and has a very low coefficient of friction; PFA is more susceptible to alternating wet and dry environments, but PFA is better than PTFE in terms of resistance to salt spray corrosion.
D) PFA is more flexible than PTFE, especially in pipeline applications, but its resistance to repeated folding is slightly less than PTFE.
E) The dielectric constant of PFA is the same as PTFE and the dissipation coefficient is very similar, however, the dielectric strength of PFA is much higher than that of PTFE.
3) Application field comparison
3.1 PTFE Application
A) PTFE is used to make cables: including connecting wires, coaxial cables, etc. This is because PTFE has excellent dielectric properties, especially in high-frequency radios. Combined with its high melting point, PTFE is a high-performance alternative to polyethylene. (mainly dispersed PTFE)
B) Due to its extremely low coefficient of friction, it is also used to make sliding bearings, gears, sliding plates, seals, gaskets, bushings, and even lubricants to reduce mechanical friction and improve energy utilization. (mainly suspended PTFE)
C) Due to its excellent chemical stability, PTFE is also used to make containers and pipes for storing and transporting active or corrosive chemicals. Ordinary PTFE pipes are white and opaque, and mainly include catheters, hoses, pipe lining pipes, braided reinforced pipes, etc. The excellent electrical properties of PTFE tubes also make them the most suitable materials in the fields of electronics and electrical engineering, mainly used for electrical insulating sheaths, chemical transportation, heat exchangers, medical urinary catheters and surgical vascular bypass.
D) Partially dispersed PTFE is also used in the manufacture of various membranes, such as clothing membranes, mask membranes, air and water treatment membranes and other high-performance PTFE membranes.
Of course, the most common applications of PTFE are non-stick pans and non-stick coatings for kitchen models.
3.2 PFA Application
PFA plastic is suitable for making corrosion-resistant parts, anti-wear parts, seals, insulating parts and medical device parts, high-temperature wire and cable insulation, anti-corrosion equipment, sealing materials, pump valve bushings, and chemical containers.
A) PFA fluoroplastics are used in cables: In the marching standard for F4 insulated RF cables, there are several specifications that specify PFA as the sheath, and their maximum operating temperature is 250°C. Where good crack resistance is required, PFA should be used. PFA can be physically foamed, and ultra-pure PFA physical foam insulation has been introduced in some countries to make small low-loss feeders for 3G, 4G, and 5G systems.
B) PFA is used in laboratory equipment, especially as pipelines for important reactions or highly corrosive chemical reactions because PFA has strong chemical resistance, optical transparency and good flexibility, which can be well avoided. Chemical contamination is caused by metal ions and therefore has important applications in the field of analytical chemistry.
C) PFA is used in the aerospace field, because of its special chemical performance.
D) In thermal power plants, PFA is used as a lining for heat exchangers. Because the high-temperature gas is passed through the PFA-lined device, the gas can be cooled without damaging the heat exchanger, thereby improving the energy utilization rate of the entire plant.
In addition, the use of PFA as the sheet lining of chemical instruments guarantees corrosion resistance, and expensive alloys and metals can be replaced by carbon steel fiber-reinforced plastics (FRPs).
8. PTFE parts making methods
Since PTFE will not flow above its melting point, it cannot be injection molded and requires special processing techniques.
A) Mold processing
Molded PTFE is processed by first compression molding the powder into preforms, and then sintering the preforms in a process analogous to sintered metal processing. This process creates geometric shapes that can then be machined, fused, and/or welded. Molded PTFE process is suitable for making simple parts directly once molding (no additional processing). Basic shapes include a block, a small plate (square or rectangle), and a short bar/pipe. Shapes range from rough discs to complex shapes but can be stripping
B) Stamping
Stamping is very suitable for thin flat gasket production. Like some PTFE sealing.
C) CNC or lathes
High-speed precision automatic lathes are designed to produce parts that small precision parts in batches. CNC machining to meet your different shape product development needs. CNC is very suitable for processing all kinds of irregular parts, and complex parts.
9. PFA parts making methods
A) Injection molding
PFA material injection molding is a big challenge for traditional injection molding manufacturers, especially for no PFA injection molding experience manufacturer. PFA injection molding is a special injection molding process in which injection molding and mold temperature are very high, and request especially modified injection machine. So any high temperature plastic material injection molding, also need a high mold temperature, high material temperature, and a special molding machine. The same high temperature material molding includes PEEK, PEI, LCP, PPS, PAS, PAI, PEI, etc.
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B) Extrusion
For the same reason. Extrusion molding of PFA plastic parts also needs a high temperature.
10. Conclusion
PTFE is sought after in the industrial field because of its very superior physical and chemical properties. However, the limitations of its processing methods also limit its application. PFA is actually an improved version of PTFE. Its performance is similar to that of PTFE, but it has very good processing performance, which solves the problems of engineers. So PFA this high temperature material is widely used in multip industries, like medical, automotive, spaceflight, industry, machinery, etc. Simple say is:
1. Both PFA and PTFE are fluoropolymers.
2. PTFE is the more commonly used fluoropolymer, commonly known as "Teflon".
3. PFA is melt processable and more versatile than PTFE, but PTFE is superior in water absorption and weathering resistance.
We leverage our deep understanding of high temperature materials including PEEK, PFA, PEI, PAI, etc. to create more reliable, better sealing, longer wearing and more cost-effective components. They are used in a variety of industrial applications including those in harsh chemical and high-temperature environments. We help customer design and injection molding a wide variety of critical high-temperature material sealing components. Contact us now to discuss our engineer with your project.
