FLUOROPOLYMER COMPARISONS

 

 

WHAT IS PTFE

 

Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by 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. Where used as a lubricant, PTFE reduces friction, wear, and energy consumption of machinery. It is used as a graft material in surgery and as a coating on catheters.

PTFE and chemicals used in its production are some of the best-known and widely applied PFAS, which are persistent organic pollutants. PTFE occupies more than half of all fluoropolymer production, followed by polyvinylidene fluoride (PVDF).

 

WHAT IS PFA

 

Perfluoroalkoxy alkane (PFA) is a semi-crystalline material developed to enhance the properties of FEP (fluorinated ethylene propylene), allowing it to be used in a wider range of environments. It is a derivative of PTFE (polytetrafluoroethylene) and a copolymer of hexafluoropropylene and perfluoro ether.

PFA is a strong, flexible, transparent fluoropolymer, used extensively for flexible tubing and fluid processing equipment. Its high purity, chemical resistance and outstanding electrical properties make it the ideal material for operations in extreme temperatures and harsh chemical environments.

WHAT IS PVDF

 

PVDF is a tough, stable fluoropolymer with distinct engineering advantages. Discovered in 1969 by Dr Heijji Kawai, PVDF has a good performance to cost ratio.

A semi-crystalline thermoplastic, PVDF is used in applications requiring the highest of purity and will withstand harsh chemicals, PVDF is one of the highest radiation resistance plastics available, only seconded by PEEK and Polyimide.

It’s highly desirable insolubility and electrical properties results from the polarity of alternating CH2 and CH2 groups on the polymer chain.

 

PVDF has a low density (1.78/cm³) compared to other fluoropolymers.

WHAT IS FEP

FEP is also known as Fluorinated Ethylene Propylene and it has different properties when compared to that of PTFE. However, it does have non-stick properties which again makes it suitable for use in applications where residues or oils are likely. FEP does have a softer makeup when compared to that of PTFE and that means that it can melt at a lower temperature which means that it is not suitable in applications that are exposed to high temperatures.

 

Along with this, it is also transparent while it is resistant to sunlight and UV which makes it suitable for use in applications that are exposed to the elements.

 

FEP is available in many forms particularly Linings and tubing. 

THE DIFFERENCE BETWEEN PTFE AND PFA

There are a few property differences between these two fluoropolymers to mention. Differences in alkoxy substituents allow PFA to be melt processable through conventional transfer moulding and extrusion techniques, whereas PTFE is not. PFA is more flexible but has a lower flex-life, so it is not as capable of enduring repetitive folding. PTFE has a slightly higher heat resistance but lacks when compared with the flow, creep resistance, and thermal stability. The melting points of PFA and PTFE are 260°C and 320°C respectively.

Operating temperatures are  180°C for PFA and 220°C for PTFE. Water absorption and weathering affect PFA slightly more than PTFE, although PFA is superior in salt spray resistance. Finally, PFA’s dielectric strength is 3 times higher than PTFE.

 

Apart from that, both materials are resistant to a wide range of chemicals, including acids, bases, gases and solvents. PFA’s chemical resistance and its weldability enhance its stability in more aggressive environments and is better suited for complex lined items due to its melt processable technique.