PTFE and PFA Similarities and Differences

Quoted from Emerson

PTFE and PFA Similarities and Differences

Introduction

The purpose of this document is to define and compare two of the most used

fluoropolymers, PTFE and PFA, in industry globally and clarify the differences between

them.

Defining PTFE and PFA

Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that

has numerous applications. The most widely known PTFE formulation is sold under the

brand name of Teflon®. PTFE was discovered by DuPont Co. in 1938.

Perfluoroalkoxy alkanes (PFA) is a copolymer of hexafluoropropylene and

perfluoroethers. It was developed after the discovery of PTFE by the same producer

(DuPont Co.). One commonly known PFA formulation is Teflon PFA.

PFA has very similar properties to PTFE, though the biggest difference between PTFE

and PFA is that PFA is melt-processed. This is accomplished through conventional

injection molding as well as screw extrusion techniques.

Area of use

PTFE is popularly used as a non-stick coating for pans and many modern items of

cookware. PTFE is often used in containers and pipes for handling reactive and

corrosive chemicals. This is because it has non-reactive properties. Another practical

application of PTFE is as a lubricant. Used in this way, PTFE helps to reduce friction

within machinery, minimize the “wear and tear,” and improve energy consumption.

PFA is generally used for plastic lab equipment because of its extreme resistance to

chemical attack, optical transparency, and overall flexibility. PFA is also often used as

tubing for handling critical or highly corrosive processes. Other applications for PFA are

as sheet linings for chemical equipment. Because of its properties, it can facilitate the

use of carbon steel fiber reinforced plastics (FRPs) as replacements for more expensive

alloys and metals.

Devices used for level measurement are frequently exposed to harsh tank

atmospheres. Aggressive media, such as acid, can corrode probes and parts in contact

with the product. Viscous and sticky products are other level measurement challenges.

These can cause build-up on the wetted parts of the transmitter and increase the risk of

affecting the measurement. Wetted parts coated in PTFE or PFA materials provide a

good resistance to corrosive products and are an effective solution for avoiding

contamination caused by product build-up.

Water based products can cause condensation on the antenna, that might affect the

level measurement. Due to the hydrophobic properties of PTFE and PFA, the

measurement will remain unaffected in case droplets of water build-up on the antenna

parts.

Differences between PTFE and PFA

PTFE, being a fluorocarbon solid, is hydrophobic, meaning that it is less easily wetted by

substances containing water. Also, PTFE possesses a very low coefficient of friction

when in contact with solids.

PFA is superior to PTFE in terms of flexibility particularly when it comes to tubing

applications. On the other hand, PFA’s flex life (i.e., capacity to endure repetitive

folding) is lower than PTFE.

PTFE is slightly more resistant to heat than PFA. PFA is more affected by water

absorption and weathering but is superior to PTFE when it comes to salt spray

resistance.

PFA has the same dielectric constant as PTFE as well as a very similar dissipation factor;

yet PFA has a dielectric strength three to four times higher than PTFE

Takeaway

Both PTFE and PFA show outstanding chemical properties for resistance to corrosive

agents, non-solubility, and non-flammability. Both are virtually identical in terms of

their electrical properties for dielectric, dissipation, and surface resistivity.

Even in critical melting point (service temperature) ratings, both materials have

identical properties. In fact, they differ significantly only with regard to cold flow (PFA

better than PTFE) and folding endurance (PTFE better than PFA). PFA has a higher creep

resistance but PTFE can withstand a higher degree of multiple folding.