Difference Between FEP and PTFE

The key difference between FEP and PTFE is that FEP is melt-processable using conventional injection moulding and screw extrusion techniques, whereas PTFE is not melt-processable.

FEP and PTFE are closely similar polymer structures. These two substances have chemical compositions that resemble each other. However, they have considerably different chemical and physical properties.

CONTENTS

1. Overview and Key Difference
2. What is FEP 
3. What is PTFE
4. Similarities Between FEP and PTFE
5. Side by Side Comparison – FEP vs PTFE in Tabular Form
6. Summary

What is FEP?

The term FEP stands for fluorinated ethylene propylene copolymer. It is produced from hexafluoropropylene and tetrafluoroethylene. The brand name for this compound is Teflon FEP. However, there are some other brand names as well, including Neoflon FEP, Daikin, and Dyneon FEP. This material is very similar in composition to PTFE and PFA. These three materials share the properties of low friction and non-reactive nature, but compared to PTFE, FEP and PFA are easily formable. Moreover, FEP is considerably softer than PTFE. In addition, FEP is highly transparent and is also resistant to sunlight.

Usually, FEP material is produced through free radical polymerization technique. This process uses a mixture of tetrafluoroethylene and hexafluoropropylene. Typically, this production process starts with peroxydisulfate, which can homolyze, generating sulfate radicals. More importantly, FEP is poorly soluble in most of the solvents we know; thus, the polymerization process is carried out as an emulsion in water in the presence of a surfactant such as PFOS.

What is PTFE?

The term PTFE stands for polytetrafluoroethylene. In common terms, it is named as Teflon. This material has fluorocarbon units as repeating units. PTFE is a synthetic fluoropolymer. The general formula of this material is (C₂F₄)_n.

PTFE is a material with high molecular weight, containing only carbon and fluorine atoms. This material exists in the solid-state at room temperature. PTFE is hydrophobic so, water cannot wet its surface. Furthermore, this material is considered to be non-reactive and useful material in the non-stick coating. This non-reactive nature arises due to the strength of the C-F bond. Due to this property, PTFE is useful in manufacturing containers and pipes. Furthermore, we can use this material as a lubricant as well. As a lubricant, it can reduce friction and the energy consumption of machinery. Besides, this material is poorly soluble in almost all the solvents.

The method of Teflon production is free-radical polymerization. We can make Teflon by polymerizing tetrafluoroethylene. However, this production process requires specialized apparatus because tetrafluoroethylene tends to explosively convert into tetrafluoromethane. It is a dangerous side reaction.

When considering its polymer properties, PTFE is a thermoplastic polymer. It occurs as a white solid at room temperature. The density of this material is about 2200 kg/m³. At very low temperatures, Teflon shows very high strength and toughness with self-lubrication properties. At high temperatures, it has good flexibility as well. Since this material is highly unreactive, the chemical species that can make a significant effect on it includes highly reactive chemical species such as alkali metals.

What are the Similarities Between FEP and PTFE

• FEP and PTFE have similar chemical compositions.
• These substances have similar corrosion resistant activity towards caustic agents.
• They contain identical dielectric constant values.

What is the Difference Between FEP and PTFE?

The term FEP stands for fluorinated ethylene-propylene copolymer while the term PTFE stands for polytetrafluoroethylene. The key difference between FEP and PTFE is that FEP is melt-processable using conventional injection moulding and screw extrusion techniques, whereas PTFE is not melt-processable. FEP has a considerably high melting point than PTEF. Moreover, PTFE is useful in manufacturing containers and pipes while FEP is superior to PTFE in some coating applications involving exposure to detergents.

The below infographic summarizes the differences between FEP and PTFE in tabular form for side by side comparison.

Summary – FEP vs PTFE

FEP and PTFE have closely similar chemical compositions. The key difference between FEP and PTFE is that FEP is melt-processable using conventional injection moulding and screw extrusion techniques, whereas PTFE is not melt-processable.

Image Courtesy:

1. “Fluorinated ethylene propylene” By Edgar181 (talk) – Own work (Public Domain) via Commons Wikimedia
2. “Perfluorodecyl-chain-from-xtal-Mercury-3D-balls” By Ben Mills – Own work (Public Domain) via Commons Wikimedia