This article clarifies the differences between fluoroplastics PTFE, FEP, PFA, and ETFE!

-- This article is translated from the original Polymer Detective Agency

Today, let's discuss a topic that many people often find confusing: What is the relationship between PTFE, FEP, PFA, and ETFE? Are they all fluoroplastics? What are the differences in their properties and applications? Is there a significant price difference? Is it difficult to process them

Many people refer to these materials interchangeably, or even simply say, "It's all Teflon anyway." However, once they use them, they encounter problems, either because the performance is excessive or the requirements are not met.

Today, we will clarify them all at once:

1. Why are there so many types of "PTFE family" materials?

2. What exactly is the difference in molecular structure?

3. What are the differences in performance?

4. How to choose application scenarios?

5. What about the price and processing difficulty?

01 Let's start with why there is modification

When it comes to the granddaddy of fluoroplastics, it has to be PTFE (polytetrafluoroethylene). Born in 1938, it has become a legend in the chemical, mechanical, electronic, and other industries, thanks to its three key properties: high temperature resistance, corrosion resistance, and low friction coefficient.

However, it also has a "fatal flaw":

• Extremely poor processability: Due to its high melting point and viscous melt, it cannot be molded using ordinary thermoplastic methods and can only be processed like metal powder through pressing and sintering;

• Weak mechanical properties: especially in terms of creep resistance and wear resistance (note: a low friction coefficient does not necessarily mean the material is wear-resistant), pure PTFE tends to "creep" under load;

• Almost zero transparency: Only white or milky white products can be made.

Therefore, people from chemical plants, cable factories, and medical device factories began to ponder whether it was possible to make it easier to process and achieve a more balanced performance while retaining its heat resistance and corrosion resistance. Thus, FEP, PFA, ETFE, and other "modified/homologous" materials of PTFE emerged.

02 Molecular structure differences

The performance of fluoroplastics ultimately stems from their molecular structure, especially the presence of fluorine atoms. Fluorine atoms have a small radius and strong polarity, and the C–F bond formed with carbon is the strongest known organic bond (with a bond energy of up to 485 kJ/mol), making fluoroplastics almost impervious to chemical attack.

Let me explain their structural differences to you in plain English:

• PTFE (Polytetrafluoroethylene)

• Basic structure – [CF₂–CF₂]–

• Structural characteristics: The carbon chain is completely encapsulated by fluorine, forming a straight chain structure with high crystallinity. It is equipped with a perfluorinated "armor" that is airtight and unbreakable, but it is too hard and slippery to process;

• FEP (Fluorinated Ethylene Propylene Copolymer)

• Basic structure: –[CF₂–CF₂]– with a small amount of –[CF₂–CF(–CF₃)]

• Structural characteristics: A small amount of hexafluoropropylene (HFP) units are introduced into the PTFE main chain, disrupting its regularity – similar to puncturing small holes in armor (by introducing HFP), making the molecular chain less regular, thus enabling melt processing;

• PFA (perfluoroalkoxyethylene copolymer)

• 

• Basic structure: –[CF₂–CF₂]– with a small amount of –[CF₂–CF(–OR_F)]

• Structural characteristics: Introducing perfluoroalkyl etheroxy side chains into the PTFE main chain improves melt flowability. Not only are holes drilled, but also mobility "pendants" (perfluoroalkyl etheroxy groups) are attached, resulting in better processing performance and higher temperature resistance than FEP;

• ETFE (ethylene-tetrafluoroethylene copolymer)

• Basic structure: –[CH₂–CH₂]– and –[CF₂–CF₂]–

• The fluorine content is lower than that of PTFE, with better toughness and easier processing. By alternating half of the "fluorine armor" with lightweight (ethylene), some chemical resistance is sacrificed in exchange for higher strength and toughness.

03 Performance Comparison

Here I provide you with an intuitive comparison table (the numerical ranges are typical values, with slight differences among different manufacturers):

A few points need to be highlighted:

• Temperature resistance: PFA is top-tier like PTFE, while FEP is slightly lower (the hexafluoropropylene unit in the FEP molecular chain contains a -CF(CF₃)-CF₂- structure, with the side group -CF₃ directly attached to the main chain carbon. The bond energy of the -C-CF₃ bond is relatively low (about 305 kJ/mol), making it prone to breaking above 260°C). ETFE has the lowest temperature resistance, but it can withstand long-term exposure up to 150°C without issues;

• Chemical resistance: The higher the fluorine content, the more stable it is. ETFE is slightly inferior, but still far superior to most plastics;

• Mechanical properties: ETFE has the best strength and toughness, suitable for making films and structural components, and can also be modified by adding fibers; PTFE is relatively soft;

• Transparency: FEP and PFA can be used to make transparent films, while PTFE cannot.

04 Application differences

The performance differences brought by different structures directly determine their division of labor in engineering:

• PTFE

Suitable for making extremely corrosion-resistant and temperature-resistant sealing rings, gaskets, bearing liners, chemical pipeline linings, expanded polytetrafluoroethylene (ePTFE) filter membranes, and medical waterproof breathable membranes

FEP

Transparent, corrosion-resistant, and heat-resistant up to 200℃, it can be extruded into films, cable sheaths, and transparent chemical pipes; with good weldability, it is used for solar photovoltaic backsheet films.

PFA

It combines the temperature and corrosion resistance of PTFE with the processability of FEP, and is used in semiconductor wet equipment pipelines, chemical storage tank linings, and precision medical tubing.

• ETFE

With strong mechanical properties, it can be used for large-scale membrane structures (such as the outer membrane of the Bird's Nest Stadium and greenhouse films), wire and cable sheaths, and anti-corrosion pipelines; it also exhibits excellent weather resistance.

05 Price difference

Market average price (for reference only, average market price of fluoroplastic in 2024, yuan/kg):

• PTFE：60~80

• FEP：120~160

• PFA: 200~300 (semiconductor grade is more expensive)

• ETFE：90~120

Note: The above is the bulk purchasing price (≥1 ton) in East China, subject to ±15% fluctuation due to crude oil/fluorspar price fluctuations.

PFA is expensive due to its complex synthesis process and high application threshold; FEP is more expensive than ETFE because of the high cost of fluorine monomers and low production volume.

06 Differences in processing difficulty

PTFE 

Processing method: Molding and sintering / paste extrusion and expansion

Core challenges:

• Ultra-high melt viscosity (10¹¹~10¹² Pa·s) → unable to melt and flow

• Large sintering shrinkage rate (3%~5%) → Difficult to control dimensional accuracy (requires compensatory design)

• Thermal cracking risk: Releases highly toxic perfluoroisobutylene (PFIB) at temperatures >400℃

FEP 

Processing method: extrusion/injection molding/blow molding (processing temperature 300~330℃)

Core challenges:

• Narrow temperature window (±10℃) → Poor fluidity at low temperatures, decomposition at high temperatures

• HF corrosion: decomposition at >350℃ produces hydrogen fluoride → corrodes equipment (requires Hastelloy alloy screws)

• Low melt strength → sagging during extrusion, uneven film thickness

PFA 

Processing method: extrusion/injection molding/blow molding (processing temperature 340~380℃)

Core challenges:

• Low melt strength → Parison sagging during blow molding (requiring radial heating compensation of the die head)

• Ultra-pure requirement: Platinum flow channel is required for semiconductor grade (to prevent metal ion contamination)

• Sensitive to surface defects: impurities > 0.1μm → film pinholes (melt filter required)

ETFE 

Processing method: extrusion/injection molding/thermoforming (processing temperature 240~270℃)

Core challenges:

• High crystallization speed → Uneven cooling may lead to warping (mold temperature needs to be controlled within ±2℃)

• Water absorption rate of 0.1% → Pre-drying is necessary (80℃/4h, moisture content ≤0.02%)

• Electrostatic accumulation: surface resistance > 10¹⁶Ω → Ionizing air is required for static elimination during cutting

07 Material selection techniques

A simple idea:

• Ultimate corrosion resistance + high temperature: choose PTFE or PFA;

• Transparency + corrosion resistance + moderate to high temperature: choose FEP or PFA;

• Strength + Weather resistance + Medium temperature: Choose ETFE;

• Limited budget → Consider ETFE first, then FEP, and finally PFA